1. MICROBIOLOGY: INTRODUCTION
i.Micro-biology is study of microorganisms like viruses, Bacteria, Protozoa, 1-celled algae and 1-celled fungi etc. Antonie van Leeuwenhoek of Holland, Louis Pasteur of France, Robert Koch of Germany and Joseph Lister of England were earlier, workers in Microbiology. Leeuwenhoek is recognized as 'pioneer' worker in microbiology, he discovered bacteria for the first time as 'animalcules' or the 'wretched beastes'. Pasteur was fist to study role of microorganisms in fermentation process involved in wine preparation. Koch studied anthrax disease, caused by bacteria Bacillus anthracis. On the basis of his study Koch proposed Law of Pathogenicity, which was later on recognized as Koch's Postulates. Koch's Postulates are not applicable for viruses & organisms causing TB and leprosy. Lister introduced antiseptic surgery and also prepared culture of bacteria first time.
ii.The two major research institutes of microbiology in world are: Pasteur Institute of Microbiology in Paris, France and Lister Institute of Microbiology, England. Workers at Lister Institute discovered 'naked' bacteria i.e. bacteria without cell of mucopolysaccharide complex. They were called 'L-form' of bacteria, named after Lister Institute. Mycoplasma like organisms, PPLO, is called L-form of Bacteria.
iii.Triple Antigen Programme includes, immunization against Diptheria, Pertusis (Whooping cough) and Tetanus. It is also called D.P.T. Oral drops of polio are delivered separately. BCG vaccines are first vaccines given to new borns after 3-4 weeks of birth. Vaccines of: Polio was discovered by Salke; Small pox by Jenner, BCG by Calmett-Guire; Anthrax by Koch and Rabies by Pasteur. Vaccines of anthrax were prepared first. Pasteur, for developing vaccines of rabies was rewarded handsomely by Czar of Russia.
2. MICROBIOLOGY: STUDY OF VIRUSES
2a) Viruses: Introduction
i.Study of viruses is called virology and Beijerinck is recognized as 'father of virology'. He reported enormous power of multiplication of viruses inside host cell. He also studied mechanism of nitrogen fixation by microorganisms like bacteria.
ii.The term 'virus' has been derived from Greek word 'virion' which means 'poison'. Viruses are defined as hyperparasites and 'filterable entities' not having any cellular organization and defined as hyperparasites and 'filterable entities' not having any cellular organization and because of this cell theory is not applicable on them. They are thus exceptions to cell theory. They form crystals when taken out of the host cell. This shows non-living nature of viruses, which was first revealed by Stanley while working on 'Tobacco Mosaic Virus'. Nucleoprotein structure of viruses was first studied by Bawden & Pierre. In nucleoprotein structure of viruses, core of nucleic acid is surrounded by coat of protein. Viruses are unique as they contain only one type of nucleic acid. Mutation in viruses was first reported by Delbruck. Mutation and enormous power of reproduction confirm living nature of viruses. Viruses are thus the only entities, which have characters of non-living and living entities both. They are thus 'connecting links' between non-living entities and lining entities.
2b) Viruses: Historical Studies
Studies in viruses started with independent works of Pasteur and Adolf Mayer. Pasteur prepared vaccines of rabies virus and used the term 'virus' for first time. Mayer reported mosaic like spots on leaves of tobacco plant infected with virus. He described the virus as Tobacco Mosaic Virus [TMV]. Ivanowski passed the cell sap of infected tobacco leaves through bacteria proof bacteria proof filter and sprayed the filtrate on healthy leaves. Mosaic spots appeared again. Ivanowski through his experiment described viruses as filterable entities. Famous conclusion of Beijerinck about viruses i.e. 'contagium vivum fluidum' means sap retains the infection of viruses (living fluid infectant). Takami of Holland studied transmission of viruses through various agencies. He observed that insects are important agencies in transmission of viruses. Insects that transmit viruses are called 'vertors'. Viruses-vector relationship is highly specific.
Culture of viruses was prepared for the first time by Ender. It was poliomyelitis virus. Hershey and Chase observed that nucleic acid is the infective part of virus. They selected Bacteriophages for their experiment. Bacteriophages are DNA containing viruses which attack bacteria. They were discovered by Twort; further studies were made by DeHerelle. Experiment of Hershey & Chase is another example which confirms status of DNA as genetic material. Safferman & Morris discovered 'Cyanophages' i.e., viruses which attack blue green algae like Lyngbya, Phormidium & Plectonema. They are also called LPP-1 on the basis of hosts. Mycophages were discovered by Sinoten. They contain ds RNA.
Issac & Lindeman discovered a protein called Interferon secreted by host cells against infection of viruses. They selected cold virus for their experiment. Gibbs described viruses in coded form which is called 'Cryptogram of viruses' Cryptogram of viruses is based on 4 pairs of characters:
First pair : Type of nucleic acid in virus i.e. R or D
Number of thread in nucleic acid 1 or 2
Second pair : Molecular weight of viruses in millions i.e. 2
Percentage of nucleic acid of the viruses 5
Third pair : Shape of the virus in total i.e. E (elongeted) or S (spiral) or
X (unknown)
Shape of the protein coat of the virus E or S or X
(E' means elongated structure or rod shaped structure with blunt ends)
Fourth pair : Host/vector i.e. S (seed plant), I(invertebrate), V(vertebrate),
B(bacterium), Fu(fungus), Di(diptra), Af(aphid), Zero or 0 (novector),
X(unknown vector) Vector of the virus X
Thus, for example R/1; 2/5; E/E; S/X is cryptogram of TMV.
For Polia Virus (Poliovirus Primus) cryptogram is R/1; 5/30; S/S; V/O.
For Influenza Virus (mixovirus influenzae) R/1; 2-3/10; S/E; V/O.
For T4 phage D/2; 130/40; X/X; B/O.
2c) Viruses: Some Terms
i.A complete virus having a core of nucleic acid and coat of protein is called virion. Protein coat of the virus is termed as capsid; units of capsid are capsomeres. A virus drops its infective part i.e., nucleic acid alone inside host cell; empty protein coat remains outside. This empty protein coat, which remains outside the host called ghost protein, disappears later on. Raw material for new protein coat of the progeny viruses is contributed by the host.
A few proteins in some viruses are enzymatic in functions e.g. lysozyme in bacteriophages, reverse transcriptase(RNA dependent DNA polymerase) in retrovituses, neuraminidase in influenza virus etc.
ii.Viriod: Subviral agent having infectious nucleic acid alone is called viroid. Viroids are RNA & particles lacks protein coat. Spindle disease in photo tuber is caused by viroid, which is PSTV. Viroids were discovered by Diener & Rayner.
iii.Prion or Slow Virus: Protein macromolecules causing infections are called prions. They lack ucleic acids. Scrappes & Kuru diseases (Severe brain infection) is sheep are caused by prions. They were first reported by Priusner who was awarded Nobel Prize for reporting Mad Cow disease caused by PrP (prion related protein). Bovine spongiform encephalopathy or Creulzfeldt Jacob disease (a type of insanity in young people), Kuru disease (the laughing death), Alzheimer's disease are caused by prions. In 1976 D.C.Gujdusek was awarded Nobel Prize for his work on prion based diseases.
iv.Viruses transmitted by insects are called Arboviruses. Viruses causing Dengue, encephalitis etc are arboviruses.
v.Viruses which contain ss-DNA are called 'Gemini viruses'. X174 phages are geminiviruses. They were reported by Sinsheimer.
vi.Viruses which enter inside host cell as intact structures, are called Adeno viruses. Well defined protein coat is absent in Adenoviruses.
vii.Virusoids or Satellilte RNAs (Rundle et. Al 1981). These are small circular RNAs similar to viroids, but are located inside the protein coat of a true virus. Virusoids required the assistance of virus for their replication.
2d) Viruses: Classification and Nomenclature
Earlier it was believed that plant viruses i.e. Phytophagineae contain RNA whereas animal viruses i.e. Zoophagineae contain DNA. This is, however, no more correct now. The only thing which is true about viruses is presence of only one type of nucleic acid. Cold virus i.e. Rhinovirus and poliovirus i.e. Enterovirus is together placed under Picorna virus.
2e) Viruses: Disease on Plants – Symptoms
i.Mosaic like spots may develop on leaves.
ii.Leaves may show rolling or curling.
iii.Leaves may show loss of chlorophyll (Chlorosis) or death of tissues (necrosis).
iv.Plants may show abnormal or stunted growth.
v.Plants may show uncontrolled cell division i.e. hyperplasia(cell number increase) and unwanted swelling i.e. Hypertrophy in host.
vi.Plants may show loss of entire inflorescence or flowers may become green i.e. virescence in flowers.
2f) Viruses: Some Common Viral Diseases
1. Plant Viral Diseases. Tobacco Mosaic, Potato Mosaic Pumpkin Mosaic, Apple Mosaic, Tulip Mosaic (Broken Tulip), Wheat Mosaic Streak, Bhindi Yellow Vein Mosaic, Potato Leaf Roll, Tobacco Leaf Curl, Papaya Leaf Curl. Banana Bunchy Top, Tomato Bunchy Top, Rice Tungro etc.
2. Animal Viral Diseases. Foot and Mouthm, Enquine encephalitis, Rinderpest, Kysanur Forest Disease (KFD) of monkeys (also humans), New Castle or Ranikhet of Fow].
3. Human Viral Diseases. Poliomyelitis, Rabies, Mumps, Measles, German Measles, Chickenpox, Smallpox (eradicated), Dengue, Encephalitis, Common cold, Flu, some gastrointestinal diseases, Yellow Fever, Herpes, Hepatitis, SARS, AIDS.
Some Important Modern Viral Diseases
1. Cancer or Carcinoma:
Despite the fact that virus causing cancer is yet to be identified, still cancer is considered like a viral disease because of typical viral symptoms like Hyperplasia & hypertrophy, are reported in cancer. Certain genes called proto-oncogenes (c-onc) are present in human cells, which are involved in normal cell function. Mutation of proto-oncogenes may give rise to oncogenes, which stimulate cell division leading to an uncontrolled growth of the cells causing cancer. All retoveiruses and some DNA containing viruses (such as poxvirus, adenovirus, Herpes virus, hepatitis-B virus etc.) possess oncogene (v.onc) in their genome. These viruses are potential cancer producing pathogens. Study of cancer is called Oncology. Temin and Baltimore's studies on Rous sarcoma virus [RSV] have provided new dimensions in the knowledge of cancer. RSV is RNA containing virus and RNA of RSV forms DNA inside host cell through reverse transcription or 'Teminism'. Newly formed DNA develops malignant tumours in host. Harmful tumor is called malignant tumours whereas tumours, which are not harmful, are termed as benign tumours. Are lethal in advanced stage.
2. Acquired Immunodeficiency Syndrome (AIDS):
AIDS is a viral disease in which our acquired immunity defense system is gradually shattered, and the patient dies of multiple infectious diseases. The first indication of AIDS disease came to light in USA in 1981 amongst a group of young homosexuals who were addicts of herion and other narcotics. Luc Montagnier (1983) and Robert Gallo (1984) discovered that a new type of retrovirus is the causative pathogen of AIDS. In 1986, The International Committee of virus Nomenclature (ICVN) named the AIDS virus as Human Immunodeficiency Virus (HIV).
Although AIDS is hardly a two and half decades old disease, it has spread virtually all over the world, becoming pandemic. According to the estimates of world Health Organization (WHO), about 52 million people in the world harbour HIV and thousands of new cases are detected every day. In India HIV infection was first detected in 1986 in some sex workers of Tamil Nadu. Since then, about 4 million cases have been detected and infection is fast spreading.
Structure of HIV:
HIV is a spherical, enveloped virus of about 90-120 nm diameter. Its genome consists of a single stranded RNA filament segmented into two identical filaments and associated with a 'reverse transcriptase enzyme'. Due to the presence of two identical filaments of RNA, HIV is considered to be 'diploid'. The envelope is comprised of a lipid bilayer derived from host cell membrane, and projecting, knob like glycoprotein spikes with pedicels formed of virus coded glycol-proteins (gp).
Pathogenesis and Symptoms:
The sentinels of our defense system are a type of white blood cells called lymphocytes. These cells are of different types to play different roles in acquired immunity. One type of lymphocytes called T4(TH) lymphocytes, play the crucial role in activation of other components of the immune system and production of antibodies. HIV attacks T4 lymphocytes and destroy them. As a result the T4 lymphocyte count in blood gradually diminishes (< 200). From the blood plasma the virus also permeates into other body fluids like semen, vaginal fluids saliva, tears, urine, sweat, breast milk etc. Gradual destruction of T4 lymphocytes through several years ultimately leads to a full blown AIDS disease, during which a patient suffers from persistent fever and diarrhea, loss of appetite and weight, weakness and fatique, body pain, dry cough, white lesions in mouth and alimentary canal and warts upon anus and genitals. Eventually, the patient loses immunity and dies of multiple infectious diseases.
Transmission:
HIV is present in blood and other body fluids of infected persons. Hence it is transmitted from one to another person through activities involving exchange or transfer of body fluids. Thus, HIV is primarily transmitted through sexual activities. Unprotected sex, sharing of syringes and needles by intravenous drug addicts, use of unsterilized syringes by doctors and health workers etc. are responsible for transmission of HIV. Transfusion of infected blood and blood products, transplantations from infected to healthy one through breast milk feeding after birth are the other potential mode of transmission of HIV.
Diagnosis:
Some genes of HIV genome code for synthesis of some antigens which are released into the blood by infected T4 lymphocytes. The immune system of body produces antibodies against these antigens, which can be detected by serological test called Elisa (Enzyme Linked Immunosorbent Assay), western blotting and PCR polymerase reaction test are the confirmatory test.
Symbol used to describe AIDS disease is ' ' (red ribbon). Noted Hollywood star Rock Hudson & Lawn Tennis Player Arthur Ashe of US were notable AIDS-causalities.
NARI (National AIDS Research Institute Puna).
NACO (National AIDS Control Organisation).
ARV (Anti Retro Viral Drug).
Prevention and Treatment:
General precautions such as safer sex and extensive use of condoms, strict screening of blood and blood products used for transfusions and tissue and organ transplantations, and extensive health education can prevent AIDS. December, 1 is observed as World's AIDS Day to arouse general awareness amongst people about HIV infection.
At present, there is no effective drug to save the immune system of AIDS patient from collapse. However, there are some drugs which are known to delay the progress of AIDS. These include Zidovudine (Azidothymidine-AZT), XQ-9302, Amphotericine-B and its methyl ester etc.
3. Pox:
Following types of pox diseases are reported in man:
Small Pox : Caused by DNA containing Pox viridae, Varoila.
Chicken Pox : Caused by DNA containing Herpes Virus, Vacicella.
German Pox : Caused by RNA containing Para influenza virus, Rubella.
Measles or Khasra : Caused by RNA containing Para influenza virus or Paramyxoviridae with minus strand RNA. AS already mentioned, vaccines of small pox were prepared by Jenner. Earlier small pox was very lethal disease in epidemic form in India. Officially, it has been eradicated from India with the help of WHO.
Natural Defenses against Viral Infections:
1. Interferons (Isaacs and Lindenmann, 1957). Interferons are antiviral proteins (a class of glycoproteins) which diffuse out from infected cells, enter into the cells in the neighbourhood and impart a defense mechanism to these cells against viral infections by inhibiting the synthesis of viral proteins. These are therefore used for therapeutic and preventive purposes in viral infections, interferons are always secreted by host cells against viral infection.
2. Body Immunity. Viruses are good antigens to induce active production of specific antibodies (by lymphocytes).
3. Immunoprophylaxis – Vaccines: Vaccines contain inactivated (attenuated) virions, which cannot cause the concerned diseases, but still act as antigens to induce antibody production by the immune system of the body.
4. Chemotherapy – Antiviral Drugs: The chemotherapeutic agents antibiotics which are used in the treatment and control of bacterial diseases are ineffective for viral diseases. However, some antiviral drugs have been prepared. These include (i) Thiosemicarbozone (for treatment and prevention of smallpox), (ii) Ribavirin or Virozole (for influenza),
(iii) Deoxyuridines, Acylovir (for herpes), (iv) Foscarnet (for hepatitis-B) etc.
2g) Viruses: Study of Bacteriophages
i.Discovery of bacteriophages is associated with Twort when he reported viral disease in bacteria. The term bacteriophages was coined by De Herelle. They are viruses, which attack bacteria. A typical bacteriophage looks like a tadpole/sperm comprising a hexagonal head of protein and a tail also a protein they show binal symmetry. Head is 1000A long and 650A in width; length of the tail is 1000A. Thus, head and tail are equal in length. Infective part of the bacteriophage in most of the cases is ds-linear DNA and it is present in hexagonal head. Joint of head and tails is neck, which is covered by collar of protein. Tail ends in end plate that develops 3 pairs of tail fibers of protein. Bacteriophages that attack E.coli are called coliphage or T-phages. They were numbered as T1, T2, T3, T4, T5, T6, T7 etc by Delburck, T2, T4, T6 etc are T-even phages T1, T3, T5, etc or T-odd phages.
ii.A bacteriophage comes into contact with the bacterial (host) cell through tail fibres. A passage is created in the host cell once the mucocomplex cell wall of bacteria is broken by lysozyme of bacteriophage. Once the passage is created, ds-linear DNA of bacteriophage is dropped inside the host cell. Empty protein coat i.e. Ghost protein remains out the host cell and disappears later on. Infective part or genetic material in X174 phages is ss circular DNA and it is RNA in MS-2 & R17 phages.
iii.Phage DNA dropped inside host cell may be virulent or temperate. Bacterial cell is destroyed if phage DNA is virulent, bacterial cell is not destroyed is phage DNA is temperate.
iv.Destruction of bacterial cell by virulent phage DNA is called lysis. The sequence of events leading to lysis of bacterial cell are:
Virulent phage DNA dropped inside bacterial cell.
Multiplication of phage DNA inside host cell i.e. Formation of prophage. Formation of complete phages. (End of latent period or period of eclipse of phages).
Destruction or lysis of bacterial cell (Total time: 15-20 minutes).*
v. A bacterial cell is not destroyed if phage DNA is temperate. Temperate phage DNA is attached with host DNA; this is called lysogeny. A lysogenic bacterial cell behaves normally till temperate phage DNA is attached. Lysogeny in bacteria was first reported by Lwoff. Lwoff also coined the term -phage for those phages in which tail terminates into single tail fibre.
Lysogeny may be of 3 types. They are -phage lysogeny; P1-phage lysogeny and mu-phage lysogeny. In -phage lysogeny, temperate phage DNA is attached with bacterial DNA at specific place i.e. at 'gal' & 'bio' genes of bacterial DNA. In P1-phage lysogeny, temperate phage DNA is attached with any place other than gal's genes. In mu-phage lysogeny, temperate phage DNA is never attached with bacterial DNA, remain in bacterial cytoplasm as plasmid.
A lysogenic bacterial cell shows different behaviour when exposed to different dosages of UV rays:
3. Microbiology: Study of Bacteria
3a) Bacteria: Introduction
i.Study of Bacteria is called 'Bacteriology'. Leeuwenhoek is recognized as pioneer worker in Bacteriology. Pasteur, Koch & Lister are other earlier workers in Bacteriology.
ii.The term bacteria were coined by Ehrenberg for the smaller 'animalcules' or the 'wretched beasts' of Leeuwenhoek. Bacteria are found everywhere and in all sorts of climates however they do not survive in acidic medium of Pickle solution or highly concentrated sucrose solution due to plasmolysis.
iii.Bacteria activity is reduced greatly at low temperature; this explains why foodstuff remains safe for longer period in cold devices like fridge and refrigerators etc. Bacteria behave in different manner in different range of temperature.
3b) Bacteria : Forms
i.On the basis of shape, bacteria may be cocci (Singular coccus), Bacilli (Bacillus), Vibrio, Spirillum etc. Cocci are spherical bacteria, smallest in size. They may be single (monoococucus), in pairs (Diplococcus), in chains (streptococcus), in bunches (staphylococcus) or cuboid (sar cinnae). Bacteria causing pneumonia are Diplococcus Bacilli are rod shaped bacteria they may be single or in chains (Streptobacilli). Majority of parasitic bacteria are rod shaped bacteria. Streptobacilli surrounded by mucilaginous sheath form Zoogloea. Vibro are comma shaped bacteria. Bacteria causing cholera are vibrio bacteria. Spirillum and spirochaete are zigzag spring like bacteria, Spirillum volutans is recognized as largest bacteria. The terms like coccus, bacillus, vibrio etc were coined by Mueller.
ii.On the basis of cilia, a bacterial cell may be:
Atrichous : Bacterial cell without cilia.
Monotrichour : Bacteria cell with single cilia.
Lopotrichous : Bacteria cell with tuft of cilia at one end.
Cephalotrichous : Bacterial cell with tuft of cilia at both the ends.
Amphitrichous : Bacterial cell with one cilia at both the ends.
Peritrichous : Bacterial cell with cilia throughout the body.
Bacteria causing cholera disease is comma shaped & Lophotrichous.
iii.On the basis of nutrition, bacteria may heterotrophy or autotroph. Heterotroph bacteria are further divided as saprophytic bacteria & parasitic bacteria. Similarly, autotroph bacteria are further divided as chemosynthetic and photosynthetic bacteria.
Bacteria, which obtain their food from dead organic matter, are saprophytic bacteria. They perform significant role of decomposers in ecosystem. Bacteria, which obtain their food from other living entity, are called parasitic bacteria. The living entity, which provides food to parasite, is termed as host. Host-parasite relation is specific. Parasite is called pathogen when it spreads in host.
Bacteria, which obtain their food through the inorganic reactions in which they participate, are called chemosynthetic bacteria. They are named after the inorganic reactions, us that they are involved. Thus, N-Bacteria S-Bacteria & Fe-Bacteria etc are examples of chemosynthetic bacteria. Chemosynthetic bacteria are basically autotroph but do not require pigment chlorophyll for energy requirement. Chemosynthetic bacteria will survive alone if chlorophyll pigment disappears from the world; rest will perish.
Bacteria, which obtain chemical energy through glucose formation, are called photosynthetic bacteria. They are autotrophs and depend on chlorophyll like pigments i.e., Bacteriochlorophyll & chlorobium chlorophyll (Bacterio viridies) for glucose formation. Green-S-Bacteria, Purple-S-Bacteria & Rhodospirillium etc. are examples of photosynthetic bacteria.
Comparison between normal and bacterial photosynthesis
Normal Photosynthesis
Bacterial Photosynthesis
1. Raw materials are CO2 & H2O
1. Raw materials are CO2 & H2S
2. H for reduction of CO2 into glucose comes from H2O
2. H- for reduction of CO2 into glucose comes from H2S.
3. Principal pigment is chlorophyll a
3. Principal pigment Bacteriochlorophyll a.
4. Intermediate H-acceptor is NADP
4. Intermediate H-acceptor is NAD.
5. PS I & PS II both are present in light phase.
5. PS I only is present in light phase; PS II is absent.
6. O2 is released as by product
6. S is released as by product
7. Biochemical reaction
6CO2 + 12H2O = C6H12O6+6H2O+6O2
7. Biochemical reaction.
6CO2 + 12H2O = C6H12O6+6H2O+12S
Generalised equation for both of the above
6CO2 + 12H2A = C6H12O6 + 6H2O + 12A
A may be oxygen or sulfur.
Photosynthesis in bacteria was first studied by Van Neil of Germany who was first to support the idea of Robino Hill that O2 released in normal photosynthesis comes from H2O and not from CO2.
3c) Bacteria: Disadvantages
Bacteria are our 'foes' as they are associated with several diseases of plants and animals including man due to parasitic mode of nutrition of some bacteria. Bacterial attack is less severe on plants than it is on animals.
Important bacterial diseases on plants are:
(a)Canker of Citrus (citrus canker) Xanthomonas citri
(b)Angular leaf spot of cotton X. malvacearum
(c)Fire blight of apples Erwinnia amylovora
(d)Crown gall of crops Agrobacterium tumefaciens
(e)Tondu of wheat Corynebacterium tritici
Important bacterial diseases on man are:
(f)Cyphillis Tryponema pallidum
(g)Plague (Black Death) Pasteurella pestis (Y. pestis)
(h)Chlorea Vibrio cholerae
(i)Anthrax Bacillus anthracis
(j)Pneumonia Diplococcus pneumonae
(k)Tuberculosis (TB) Mycobacterium tuberculoses
(l)Typhoid (Enteric fever) Salmonella typhi
(m)Bacterial dysentery Bacillus dysentrae (Shigella)
(n)Amoeboid dysentery Entamoeba histolytica (Protozoa)
(o)Tetanus (Lock jaw) Closteridium tetani
(p)Ptomaine (deadly food poisoning) Closteridium botulinum
(q)Leprosy Bacillus lepri (Mycobacterium lepri)
(r)Diptheria Corynebacterium diptherae
(s)Erysepalas (deadly blood Streptococcus
Poisoning; Death of RBC's)
(t)Whooping cough Bordetella partusis
(u)Gonorrhoea Neisseria gonorrhoae
Bacterial diseases like cholera, typhoid, dysentery etc are water borne diseases: tuberculosis, plague etc are air-borne diseases whereas disease like tetanus spreads through wounds. Syphilis is transmitted through sexual contact. Transmission of leprosy through contact is a matter of dispute. India based Mother Teresa was awarded Nobel Prize for her service to leprosy patients in West Bengal and other parts of India.
3d) Bacteria: Advantages:
Bacteria are our friends as they are associated with several advantages in various forms. Some of them are:
i.Bacteria & Ecosystem: Saprophytic bacteria along with saprophytic fungi perform useful role of decomposers in ecosystem. Decomposition of organic matter in absence of O2 is called putrefaction and breakdown of organic matter in presence of O2 is called decay. Highly un-decomposed organic matter is litter; partly decomposed organic matter is humus and highly decomposed organic matter is called humus.
ii.Bacteria & Industry: Lactobacillus laciti and Streptococcus lacti convert milk into curd. Acetobacillus aciti changes sugar solution into vinegar. Flavour in tea leaves by Micococcus condensa and in tobacco leaves by Micococus megatherium develops due to fermentation activity of bacteria. Retting involves separation of plant fibers after decomposition of non-cellulosic materials by various species of Closteridium like C.butyricum and C.felsineum.
iii.Bacteria and N-cycle system: Nitrogen is first essential element in terms of requirement for proper growth of plants. It is required in protein synthesis, chlorophyll synthesis and also in synthesis of nucleic acids. Plants cannot utilize molecular nitrogen directly. The plants mainly in the form of nitrates absorb it. Nitrogen changes into nitrate via ammonia formation. Some bacteria control N-cycle, which comprises Nitrogen fixation, Nitrification and Denitrification. Nitrogen fixation involves conversion of N2 into ammonia. Bacteria which participate in N-fixation are Closteridium, Azotobacter and Rhizobium etc. Closteridium and Azotobacter and asymbiotic biological N fixing bacteria whereas Rhizobium is symbiotic biological N-fixing bacteria are present in root nodules of Leguminous or papilionaceous plants. Klebsiella is leaf nodule N-fixing bacteria. Frankia is non-leguminous N-fixing bacteria 'nif' genes control biological N-fixation. Mechanism of biological N-fixation by bacteria was first studied by Heijerinck whereas Winogradasky studied biological N2 fixation by some blue green algae.
Conversion of NH3 into nitrite is termed as initial stage of Nitrification. A bacterium which participates in initial stage of nitrification is nitrosomonas Conversions of nitrite into nitrate is called final stage of nitrification. Nitrobacter is the bacteria which participates in final stage of nitrification.
Release of Nitrogen from Macromolecules of Nitrogen is called denitrification. Bacillus denitrificans is the bacteria involved in denitrification. The summary of Nitrogen cycle is given in the following figure:
Summary of various N-fixing bacteria:
Azotobacter, Thiobacillus, Mycobacterium etc. : Free living & aerobic.
Closteridium Klebsiella : Free living & anaerobic.
Rhizobium, Aopzprirllium Frankia : Symbiotic & anaerobic
Citrobacter : Symbiotic and anaerobic
Bacteria & Antibiotics: Though first antibiotic penicillin was obtained from ascomycetes fungus Penicillium notatum by Alexander Flemming in 1929, yet soil-borne bacteria Streptomyces of actinomycetes (ray fungi) are rich source of various types of antibioitics. Antibiotics are chemical inhibition. The term 'antibiotic' was coined by Salman Waksman. Antibiotics are known as chemotherapeutic agents. Some of the antibiotics extracted from bacteria are bacitracin, subtilin, polymyxin, gramicidin etc.
Salient features of some antibiotics chemotherapeutic agents
Name of the antibiotics
Name of the discover
Source of antibiotics
Action of antibiotics
Penicillin
Alexander Flemming
P. notatum
P. chrysogenum
Breaks muco complex cell wall of bacteria.
Streptomycin
Waksman
Streptomyces griesus
Inhibits synthesis of 30S fragment of ribosome in bacteria.
Erythromycin
Mc Guire
S. erythreus
Inhibits synthesis of 50S fragment of ribosome in bacteria
Chloromycin
Burkholder
S. venezualae
Inhibits initiation of protein synthesis in bacteria.
Aureomycin
Duggar
S. auerofaciens
Inhibits formation of tRNA amino acid complex.
Terramycin
Pfizer Ltd.
S. rimosus
Inhibits formation of tRNA amino acid complex.
Penicillin is not broad spectrum antibiotic because it is more active on gram positive bacteria, less effective on gram negative bacteria. Streptomycin is first brad spectrum antibiotic which is equally active on gram positive and gram negative bacteria both.
Bacteria & Miscellaneous uses
(a)Aerobacter aerogenes decomposes DDT whereas Flavobacterium and Corynebacterium decompose 2, 4-D etc. DDT and 2, 4-D are non-biodegradable chemicals, which may be lethal even.
(b)Bacillus pudita, pseudomonas and some other oil-eating bacteria help in cleaning up oil spills. They thus help in preventing water pollution of seas/oceans caused due to oil refineries.
(c)Anand Mohan Chakroborty has developed genetically engineered bacteria named Superbug that feeds on oil spills.
(d)Bacterium Methylophylus methylotropous is source of single cell protein (SCP) the product was called 'Pruteen'. Fungus Fusarium is also used for the purpose i.e. preparation of mycoprotein on larger scale.
(e)Batch culture & continuous culture are two main methods of fermentation on larger scale. The former is closed system whereas latter is open system.
3e) Bacteria: Classification:
Bacteria and blue green algae are prokaryotes as they lack true nucleus in absence of nuclear membranes. They were placed together under Schizophyta by Cohn in 1853. However, Whittaker in his famous five kingdom classification placed prokaryotes under Monera, a term coined by Stanier. Bergey's Manual in Determinative Microbiology (1974) is widely recognized in medical science:
3f) Bacteria: Structure of a Cell:
i.Bacteria is placed in plant kingdom because contains rigid & non-living cell wall which is outer most in position. Bacterial cell wall is made up of muco-complex or peptidoglycan. Muco-complex is a complex formed between few simple sugars and proteins: The sugars are N-Acetyl glycosamine (NAG) and N-Acetyl Muramic Acid (NAM) or murein. Protein of mucocomplex are formed by few amino acid i.e. Glycine, Lysine, glutamic acid and diaminopimelic acid (DAP): Peptidoglycan linkage of bacterial cell wall is broken by lysozyme enzyme of bacteriophages or by antibiotic penicillin.
Staining of bacterial cell wall was first introduced by Christian Gram. It involves staining of bacterial cell with crystal-violet (Gram Stan). With this bacterial cells appear deep violet coloured. Crystal violet staining is followed by treatment with organic solvent. If deep violet colour is retained by bacterial cell after treating with organic solvent then bacteria are called Gram positive. If deep violet colour is lost after treating with organic solvent then bacteria are termed as Gram negative.
Difference between Gram Positive and Gram Negative Bacteria
Mucocomplex content is high in gram positive bacteria
Mucocomplex content is low in gram negative bacteria
Teichoic acid is present
Teichoic acid is absent
Penicillin is more effective
penicillin is less effective
Lipid content is low, this explains why deep violet colour is retained after treatment with organic solvent
Lipid content is high, this explains why deep violet colour is lost after treatment with organic solvent lipid is dissolved in organic solvent
Example: Bacillus subtilis (Haybacillus)
Example: E. coli
Mucocomplex cell wall is surrounded by slime layer, which changes into capsule layer during unfavourable condition. Capsulated stage in bacteria is resistant to antibiotics to larger extent.
ii.True nucleus is absent in bacteria because nuclear membrances are absent in prokaryotes, Incipient nucleus in prokaryotes is called 'NUCLEOID' and it is represented by a double stranded circular DNA only. Nucleolus is also absent. ds circular DNA without proteins in bacteria may also be considered as bacterial chromosome.
iii.Membranou cell-organelles remain absent in prokaryotes including bacteria, however in some bacteria, inward folding of cell membrane may form structures like mesomomes & chromatophores: Mesosomes, first reported by Frtiz-James, develop in aerobic bacteria for complete breakdown of macromolecules in presence of O2. Definite role of mesosomes is also reported during replication of DNA. Chromatophores or photosynthetic lamellae develop for photosynthesis. Ribosomes for protein synthesis are 70S in size and they remain embedded directly in cytoplasm in absence of ER. Since ribosomes remain embedded directly in cytoplasm this explains why density of prokaryotic cytoplasm is more than density if eukaryotic. The two fragments of 70S ribosomes are 50S & 30S.
Carbohydrates are stored in the form of glycogen whereas storage of protein is in the form of volutin granules. Storage of inorganic substances is in the form of granulose.
iv.A bacterial cell may or may not have flagella. Bacterial flagellum is different from eukaryotic flagellum because bacterial flagellum is made of flagellin proteins and 9+2 arrangement is also not present. Flagella like structures but much smaller in length are called fimbrae or Pilli. Fimbrae or pili may be specialized to form sex pili, which play significant role during conjugation in bacteria.
v.Extra inheritable material, present in cytoplasm bacterial cell is called 'plasmid' discovered by Lederberg. Some plasmids are capable of combining with main genetic material i.e. DNA of bacterial cells. They are called Episomes. Therefore, it may be concluded that all episomes are plasmids but all plasmids are not episomes. R Factor in bacteria is purely a plasmid; it provides resistance against antibiotic. The other examples of common plasmids in bacteria are pBR322 and Col-factor, which produces colicin. F factor (fertility-factor) in bacteria is an example of episome. It plays significant role in conjugation. Bacterial cell, which contains F factor, is cytoplasm called F+ cell or donor cell and bacterial cell, which lack F factor, is called F– cell or recipient cell. Bacterial cell is termed as High frequency Recombinant (HFR) when F factor combines with DNA of bacteria.
3g) Bacteria: Reproduction:
i.Asexual reproduction through binary fission is very common method of reproduction in Bacteria. It takes place during favourable conditions. One parent bacterial cell splits to form two daughter bacterial cells in binary fission.
A bacterial cell divides every minute; time required to form 128 cells of bacteria will be? Number of divisions required to form 128 bacterial of cells will be:
1 Cell ---- Istdiv-----2 Cells ----IInddiv----4 Cells ----IIIrddiv---8 Cells---IVthdiv---16 Cells---Vthdiv---32 Cells----VIthdiv-----64 Cells---VIIthdiv---128 cells. Thus, numbe of divisions required to form 128 bacterial cells=7. Therefore, time required to form 128 bacterial cells: 7 divisions X 1 minute = 7 minutes.
A bacterial cell divides every minute it takes one hour to fill a cup; time required to fill half & quarter of the cup will be?
From the above, it is clear that: (X + 1+ 1) + 60. Hence, X = 58 minute.
Therefore time required to fill ¼ cup will be: 58 minutes and time required to form ½ cup will be 58 + 1 = 59 minutes.
ii.Conidia like structure develops during asexual reproduction in fungi like bacteria i.e., in Actinomycetales.
iii.Bacteria forms endospore during unfavourable conditions it is the hardest structure of bacteria. Bacterial cell under goes capsulated stage and entire inner contents shrink to form endospore. One bacterial cell forms one endospore during unfavourable conditions.
iv.Sexual reproduction or syngamy involves fusion of two haploid units or gametes. The two haploid units are formed after meiosis or reduction division. In bacteria meiosis or reduction division is not possible because bacterial cell contains single chromosome. This sexual reproduction or syngamy is not reported in bacteria in absence of meiosis. Sexual reproduction plays significant role in evolution because it is main method of genetic recombination in living entities. Though well-defined sexual reproduction is missing in bacteria, yet bacteria shows some important methods of genetic recombination.
3h) Bacteria: Methods of Genetic Recombination:
Three main methods of genetic recombination are reported in bacteria. They are conjugation, transformation and transduction. In addition to these three, sexduction is also a method of genetic recombination in bacteria.
i.Conjugation, a method of genetic recombination in bacteria was first reported by Lederberg & Tatum in bacterium E. coli. It involves transfer of 'F factor' from donor bacterial cell F+ to recipient bacterial cell F– through direct contact. The two types of bacterial cells i.e. F+ and F– come in contact with each other through sex pili and a passage called conjugation tube develops for transfer of F factor. F factor is doubled before transfer and F– cell becomes F+ after transfer of F factor. Thus genetic recombination takes places in recipient cell:
ii.Transformation another method of genetic recombination in bacteria was first reported by Griffith in 1926-27 in bacterium Diplococcus pneumonae. The event is in vitro (in Lab) only and not in vivo (not in nature). It involves transfer of a part of DNA of donor bacterial cell to recipient bacterial cell through medium solution. Part of DNA of donor bacterial cell, which is transferred, is called transformosome. It is 1/1000 of original DNA content of donor bacterial cell.
Griffith prepared two strains of Diplococcus pneumonae i.e. non-capsulated, non-virulent type (R-Type) and capsulated, virulent type (S-Type). The two types were infected in mice and following observations were observed:
R-Type : all mice healthy
S-type : all mice died of pneumonia
S-type Heat killed : all mice healthy
R-type + S-type (heat killed) : all mice died of pneumonia
The observation that all mice died when R-type + S-type (heat killed) was injected, prompted Griffith to conclude that there was transfer of 'something' from heat killed S-type to R-type, which made R-type virulent. Griffith could not identify this something all that time. Avery, Macleod & McCarty (Avery et al) later on repeated the experiment of Griffith in 1948 and identified that this something was part of DNA of S-type (heat killed), which was transferred to R-type. These parts of DNA called transformosome made R-type virulent. Avery et al. with this finding established the status of DNA as every genetic material. Work of Hershey & Chase involving DNA as infective part of Bacteriophage is another experiment, which establishes status of DNA as genetic material.
iii.Transduction yet another method of genetic recombination, was discovered by Zinder & Laederberg in bacterium Salmonella typhi. It involves transfer of a part of DNA (from donor bacterial ell to recipient bacterial cell through bacteriophages. The part of DNA transferred is about 1/1000 of original DNA content. The event is rare but it is reported in nature. New phages may carry a part of DNA of bacterial cell. Bacterial cell B' (recipient cell) receives a part of DNA of Bacterial cell A' (donor cell) through bacteriophages. In generalised transduction, recipient cell receives plasmid of donor cell.
iv.SEXDUCTION was reported by Addelburg & Burns in E. coli. They observed that during conversion of HFR into F+ dissociation of F factor is not always accurate. F factor some times carries a part of main DNA of Bacteria. This F factor with a part of bacterial DNA is called F prime of F' factor. When this cell conjugates and transfers the gene attached with F prime, recipient cell becomes 'partially diploid' for the particular gene. This phenomenon has been described as sexduction in bactera.
Methods of genetic recombination in bacteria are tools of genetic engineering that is a nascent branch of biotechnology genetic engineering aims at developing superior character of desired results by manipulating at gene level. Bacterial plasmids like pBR322, Ti factor (Tumor inducing factor) etc are of immense value in genetic engineering. Several diseases like Diabetes etc may be cured with the help of genetic engineering. High yielding & disease resistant varieties of crops may also be developed with the help of genetic engineering. Thus genetic engineering in near future may prove boon to mankind: but at the same time it may prove to be a curse as well. The biggest threat of genetic engineering is of biological warfare. Pathogens of several dreaded diseases of past may be regenerated again which may cause huge destruction to mankind.
4. Microbiology: Miscellaneous
i.Mycoplasma were discovered by Nocard & Roux as Mollicutes. They are 'L-form' of bacteria, which are filterable like viruses. They are called 'L-form' because they lack well defined mucocomplex cell wall of typical bacteria. Due to this they are polymorphic entities i.e. they may exist in several forms; hence the popular name of 'joker' in biological kingdom. Due to absence of cell wall, mycoplasma looks like a boiled fried egg. Mycro Plasma are gram negative and are not affected by antibiotics penicillin (inhibitor of cell wall formation) but are inhibited by tetracyclin Mycoplasma has a definite cellular organization; a cell of mycoplasma is the smallest cell. Genetic material is ds DNA that is highly coiled and attached with a disc at one end. Cytoplasm contains RNA & 70S ribosomes. Mycoplasma require sterols for the growth. Some biologists place mycoplasma between viruses & bacteria. Dieseases like 'Little leaf of brinjal' and 'witches broom' of sugarcane etc are caused by Mycoplasma and related mollicutes placed under Pleuro Pneumonia like organism (PPLO). Some microbiologists have named mycoplasma like organism as Spiroplasma, which cause diseases on plants.
ii.Rickettsias are tiny obligate, gram negative pleomorphic but walled parasites present in blood sucking insects like ticks, lices, mites etc. They may be rod-shaped or spherical. They have mucopeptide cell wall and genetic material is ds circular DNA. Cytoplasm contains RNA and 70S ribosomes. They are sensitive to antibiotics and multiply by fission. Diseases like Typhus, Q-fever, Trench fever rocky-mountain spotted fever etc are caused by Rickettsias. Ricketts first observed them but Proper description was made by Rocha-levis later on.
iii.Spirochaetes are protozoa like aflagellate bacteria. They have an axial filament called crista, which is spirally coiled. They show gliding movement and multiply by fission. Diseases like Syphilis, Jaundice etc are caused by them.
iv.Chlamydiae: They are Gram(-ve) intracellular parasites of about 0.25 m. size, often grouped along rickettsiae. However, their reproductive cycle differs from rickettsiae in the formation of initial or reticulate bodies (RB) and elementary bodies inside host phagosome. They have cell wall similar to typical bacterial wall. They lack ATP formation and obtain the same from outside chlamydiae are thus energy parasites. The common diseases caused by chlamydiae include Conjuntivitis, nongonococcal urethritis and lymphogram losa venecatum, pneumonia and bronchopneumonia, psittacosis.
SARS (Severe Acute Respiratory Syndrome), this viral disease was first reported in Guangdong Province in Southern China in Nov. 2002. The cause of SARS was identified as a member of the Corona Viridae (single stranded RNA viruses).
SARS causing virus transmitted by droplets from coughs and sneezes.
It produces severe form of pneumonia, fever of 100.4 oF (some time with chills), headache, bodyaches and malaise.
High Security Animal Disease laboratory Bhopal, is the main center where SARS virus study carried out.
Vaccination:
Vaccination is a preventative strategy that aims to stimulate the host immune system, by exposing it to the infectious agent in question in an inactivated or incomplete form. There are four types of virus vaccines:
1. Attenuated (='weakened') vaccines contains 'live' viruses, but ones whose pathogenicity has been greatly reduced. E.g. Polio Virus vaccine developed by Albert Sabin in the 1960s. The cowpox virus used by Edward Jenner in his pioneering vaccination work in the late 18th century was a naturally occurring attenuated version of the smallpox virus.
2. Inactivated vaccines contain viruses which have been exposed to a denaturing agent such as formalin. This has the effect of rendering them non-infectious, while at the same time retaining their ability to stimulate an immune response. Vaccines directed against influenza are of this type.
3. Subunit vaccines depend on the stimulation of an immune response by just a part of the virus. Since the complete virus is not introduced, there is no change of infection, so vaccines of this type have the attraction of being very safe. Subunit vaccines are often made using recombinant DNA technology; the first example to be approved for human use was the hepatitis B vaccine, which consists of part of the protein coat of the virus produced in specially engineered yeast cells.
4. DNA vaccines are also the product of modern molecular biology techniques. DNA coding for virus antigens is directly injected into the host, where it is expressed and triggers a response by the immune system. Vaccines of this type have not so far been approved for use in humans.
Satellite Viruses:-
i.Satellite viruses are also known as 'incomplete viruses'.
ii.The replication of this virus is dependent of coinfection of a second 'helper' virus.
iii.Satellite virus and helper virus are separate entities; they encode their own capsids and infect the cell independently.
Saturday, April 10, 2010
स्टेम सेल से श्वास नली का सफल प्रतिरोपण
श्वास नली का सफल प्रतिरोपण
चिकित्सा जगत में तीसरी बार श्वास नली का प्रत्यारोपण किया गया है
ब्रिटेन में 10 साल के लड़के की श्वास नली का उसके ख़ुद के स्टेम सेल से सफल प्रतिरोपण किया गया है.
चिकित्सा जगत में इस ऑपरेशन को बड़ी उपलब्धि माना जा रहा है. क़रीब नौ घंटे तक ग्रेट ऑरमंड स्ट्रीट हॉस्पिटल में चले इस ऑपरेशन में श्वास नली के लिए स्टेम सेल इस लड़के के शरीर से ही लिया गया.
हालाँकि श्वास नली का दुनिया में पहला प्रतिरोपण 2008 में स्पेन में किया गया था, लेकिन इस ऑपरेशन में श्वास नली के बहुत छोटे हिस्से का प्रतिरोपण कर दिया गया था.
डॉक्टरों के कहना है कि लड़के के स्वास्थ्य में तेज़ी से सुधार हो रहा है और सामान्य रूप से सांस ले रहा है.
उपलब्धि
इस लड़के को जन्म से ही सांस लेने में मुश्किल होती थी और इसकी वजह थी उसकी श्वास नली का बेहद संकरा होना. डॉक्टरों के अनुसार जन्म के समय लड़के की श्वास नली सिर्फ़ एक मिलीमीटर चौड़ी थी.
पहली बार किसी बच्चे का उपचार स्टेम सेल से किया गया है और ये अब तक की सबले लंबी प्रत्यारोपित श्वास नली है
मार्टिन ब्रिशेल
डॉक्टरों ने इस लड़के की श्वास नली का रास्ता चौड़ा करने के लिए पिछले साल नवंबर में भी ऑपरेशन किया था, लेकिन ये सफल नहीं हो सका और मरीज़ को कई दिक्कतों का सामना करना पड़ा.
इसके बाद डॉक्टरों ने लड़के के बोन मैरो (मेरु रज्जा) से स्टेम सेल लेकर धातु की श्वास नली के अंदर और बाहर प्रत्यारोपित करने का निर्णय लिया. डॉक्टरों को भरोसा है कि अगले महीने तक स्टेम सेल स्पेशलाइज़्ड सेल में बदल जाएगी.
दो साल पहले दो बच्चों की माँ 30 वर्षीय क्लाउडिया कास्टिलो स्टेम सेल से बनी श्वास नली को प्रत्यारोपित करने वाली पहली शख्स थीं. तपेदिक के चलते उनकी श्वास नली ख़राब हो गई थी.
चिकित्सा जगत में तीसरी बार श्वास नली का प्रत्यारोपण किया गया है
ब्रिटेन में 10 साल के लड़के की श्वास नली का उसके ख़ुद के स्टेम सेल से सफल प्रतिरोपण किया गया है.
चिकित्सा जगत में इस ऑपरेशन को बड़ी उपलब्धि माना जा रहा है. क़रीब नौ घंटे तक ग्रेट ऑरमंड स्ट्रीट हॉस्पिटल में चले इस ऑपरेशन में श्वास नली के लिए स्टेम सेल इस लड़के के शरीर से ही लिया गया.
हालाँकि श्वास नली का दुनिया में पहला प्रतिरोपण 2008 में स्पेन में किया गया था, लेकिन इस ऑपरेशन में श्वास नली के बहुत छोटे हिस्से का प्रतिरोपण कर दिया गया था.
डॉक्टरों के कहना है कि लड़के के स्वास्थ्य में तेज़ी से सुधार हो रहा है और सामान्य रूप से सांस ले रहा है.
उपलब्धि
इस लड़के को जन्म से ही सांस लेने में मुश्किल होती थी और इसकी वजह थी उसकी श्वास नली का बेहद संकरा होना. डॉक्टरों के अनुसार जन्म के समय लड़के की श्वास नली सिर्फ़ एक मिलीमीटर चौड़ी थी.
पहली बार किसी बच्चे का उपचार स्टेम सेल से किया गया है और ये अब तक की सबले लंबी प्रत्यारोपित श्वास नली है
मार्टिन ब्रिशेल
डॉक्टरों ने इस लड़के की श्वास नली का रास्ता चौड़ा करने के लिए पिछले साल नवंबर में भी ऑपरेशन किया था, लेकिन ये सफल नहीं हो सका और मरीज़ को कई दिक्कतों का सामना करना पड़ा.
इसके बाद डॉक्टरों ने लड़के के बोन मैरो (मेरु रज्जा) से स्टेम सेल लेकर धातु की श्वास नली के अंदर और बाहर प्रत्यारोपित करने का निर्णय लिया. डॉक्टरों को भरोसा है कि अगले महीने तक स्टेम सेल स्पेशलाइज़्ड सेल में बदल जाएगी.
दो साल पहले दो बच्चों की माँ 30 वर्षीय क्लाउडिया कास्टिलो स्टेम सेल से बनी श्वास नली को प्रत्यारोपित करने वाली पहली शख्स थीं. तपेदिक के चलते उनकी श्वास नली ख़राब हो गई थी.
टीबी बैक्टीरिया को मारेगा उसी का रसायन
टीबी के इलाज में इसे महत्वपूर्ण खोज माना जा रहा है
वैज्ञानिकों का कहना है कि उन्होंने टीबी के इलाज का नया तरीका खोज निकाला है.
विज्ञान की शोध पत्र नेचर केमिकल बायलॉजी में प्रकाशित शोध के अनुसार ब्रिटेन और अमरीका के वैज्ञानिकों ने टीबी बैक्टीरिया के एक ऐसे रसायन का पता लगाया है जो टीबी बैक्टीरिया को स्वंय समाप्त कर देगा.
लेकिन बीबीसी संवाददाता का कहना है कि ये देखना होगा कि अंतरराष्ट्रीय दवा कंपनियाँ इस ओर कितना ध्यान देती हैं क्योंकि शोध की ये प्रक्रिया काफ़ी लंबी है.
ग़ौरतलब है कि टीबी के कारण विश्व में हर साल लाखों लोगों की मौत हो जाती है.
शोधकर्ता इस बीमारी के ऐसे बैक्टीरिया के सामने आने से चिंतित हैं जिन पर दवाओं का असर नहीं होता.
विश्व स्वास्थ्य संगठन के अनुमान के मुताबिक एमडीआर टीबी यानी मल्टी ड्रग रिज़िसटेंट टीबी के लाखों मामले हर साल सामने आते हैं.
इनमें से ज़्यादातर मामले भारत, चीन और पूर्व सोवियत संघ से होते हैं.
मल्टी ड्रग रिज़िसटेंट टीबी बीमारी का वो रूप है जिसमें कम से कम दो मुख्य तरह की टीबी पर दवाओं का असर नहीं होता है.
इस तरह की टीबी के लिए अलग किस्म की दवाओं का इस्तेमाल करना पड़ता है.
ये दवाएँ ज़्यादा नुक़सानदेह और मंहगी होती हैं और साथ ही ठीक होने में समय भी ज़्यादा लगता है.
उल्लेखनीय है कि टीबी की रोकथाम करने वाली मौजूदा दवा सौ फीसदी प्रभावी नहीं है और इसका इस्तेमाल भी लगातार कम से कम छह महीने करना पड़ता है.
इसका मतलब यह है कि बहुत से लोग अगर इस कोर्स को पूरा नहीं करते तो इस रोग का आक्रमण फिर से होने का ख़तरा बना रहता है.
जलवायु परिवर्तन से बिगड़ता प्राकृतिक संतुलन
ग्लोबल वॉर्मिंग के चलते हो रहे जलवायु परिवर्तन के कारण प्रकृति का संतुलन बिगड़ने लगा है. अगर कुछ वैज्ञानिकों की मानें तो यह ग्लोबल वॉर्मिंग एक प्रकृतिजन्य प्रक्रिया का हिस्सा है, जो एक निश्चित समय चक्र पर लगातार होती है.
इसके कारण पृथ्वी पर रहने वाली सभी प्रजातियों को लगातार परिवर्तनशील होना पड़ता है. प्राकृतिक रूप से होने वाली ये प्रक्रियाएं प्रजातियों के क्रमिक विकास के लिए फायदेमंद होती है.
हालांकि यह सिद्धांत पूरी तरह मान्य नहीं है और देखा जाए तो मानव गतिविधियों के कारण ग्लोबल वार्मिंग के प्रभावों में तेजी से जलवायु परिवर्तन तेज हो गया है. अनेक पर्यावरणविदों और वैज्ञानिकों ने आशंका जताई है कि ग्लोबल वॉर्मिंग के चलते हो रहा जलवायु परिवर्तन निकट भविष्य में कई प्रजातियों के विलुप्त होने का सबसे बड़ा कारण हो सकता है.
जलवायु परिवर्तन का सबसे दूरगामी प्रभाव पड़ता है उस क्षेत्र में रहने वाली प्रजातियों पर. तापमान के कुछ डिग्री सेंटीग्रेट ऊपर नीचे होने भर से कई प्रजातियां के विलुप्तीकरण का खतरा पैदा हो जाता है. ग्लोबल वॉर्मिंग के प्रभावों का सबसे ज्यादा दुष्प्रभाव पड़ता है क्षेत्र के स्थानीय पारिस्थितिक तंत्र पर, जो बहुत ही नाजुक होते हैं.
ध्रुवीय भालू पर ग्लोबल वॉर्मिंग की सीधी मार
एक ओवरहीटिंग जलवायु वैश्विक परिस्थितियों में कितना बड़ा परिवर्तन पैदा कर रही है और मौजूदा नाजुक पारिस्थितिकी प्रणालियों में वर्तमान प्रजातियों को कितना नुकसान हो सकता है, नीचे दिए गए कुछ उदाहरणों से समझा जा सकता हैः
उत्तरी गोलार्द्ध में स्थित कनाडा के बर्फीले मैदानों से ध्रुवीय भालू गायब होते जा रहे है, क्योंकि कनाडा में बर्फीला क्षेत्र लगातार कम होता जा रहा है. ध्रुवीय भालुओं के प्राकृतिक रहवास में बर्फ उनकी खाद्य श्रृंखला के लिए सबसे ज्यादा महत्वपूर्ण तत्व है. आर्कटिक समुद्र में भालू शिकार के लिए सिर्फ बर्फ पर निर्भर हैं. यह जीव खुले समुद्र में सील व मछलियों का शिकार करते समय बर्फ को एक अस्थायी मंच के रूप में उपयोग करता है.
विशेषज्ञों का मानना है कि आर्कटिक समुद्र में बर्फ प्रति दशक 9 प्रतिशत की दर से पिघल रही है. यह समुद्र ही ध्रुवीय भालू का एकमात्र निवास स्थान है, जहां उनके अस्तित्व पर खतरा छा गया है.
दक्षिण अमेरिका में सालाना प्रजनन के लिए समुद्री कछुए ब्राजील के समुद्र तटों पर अपने अंडे देने आते हैं, तटों की नरम रेत पर घोंसले बनाने की सबसे बड़ी वजह है वहां का मुफीद तापमान. रेत का तापमान कछुओं के अंडों का लिंग निर्धारण करता है. ठंडी रेत से मादा कछुए और अगर रेत गरम हो तो नर कछुए अंडों से बाहर आते हैं और इस संतुलन से वंशवृद्धि निश्चित होती है.
लेकिन ग्लोबल वॉर्मिंग से समुद्र का स्तर बढ़ने लगा है और अलग-अलग स्थानों पर दिए गए अंडों के पानी में डूबने का खतरा बना हुआ है. ग्लोबल वॉर्मिंग के
पिघल रहे हैं ग्लेशियर कारण पानी का तापमान भी अनिश्चित हो गया है. इससे रेत के तापमान में घट-बढ़ से अंडों से सभी मादा या नर कछुए पैदा होने का डर है, जिससे इस प्रजाति का प्राकृतिक संतुलन बिगड़ रहा है.
उत्तरी अटलांटिक के सबसे बड़े और शानदार प्राणी व्हेल से मानव द्वारा शोषण का एक लंबा इतिहास जुड़ा है, लेकिन अब समुद्र के पानी के तापमान में वृद्धि के कारण व्हेल का आहार प्रभावित हो रहा है.
प्लांक्टन और कवक पर आश्रित व्हेल को अब खाने की तलाश में काफी दिक्कतें आ रही हैं. ग्लोबल वॉर्मिंग के चलते पानी का तापमान बदला है, जिससे प्लांक्टन और कवक की संख्या में अप्रत्याशित कमी देखी गई है.
चीन के विशाल पांडा का भविष्य अनिश्चित बना हुआ है. इसके आवास दक्षिण पश्चिमी चीन के पहाड़ी क्षेत्रों में पाए जाने वाले बांस के वन अब खंडित हो चुके हैं. विशाल पांडा की आबादी अब नगण्य है और इनका मुख्य आहार बांस है. चीन के बांस के जंगल एक नाजुक पारिस्थितिकी तंत्र है और ग्लोबल वार्मिंग के कारण जलवायु परिवर्तन से प्रभावित हैं
इसके कारण पृथ्वी पर रहने वाली सभी प्रजातियों को लगातार परिवर्तनशील होना पड़ता है. प्राकृतिक रूप से होने वाली ये प्रक्रियाएं प्रजातियों के क्रमिक विकास के लिए फायदेमंद होती है.
हालांकि यह सिद्धांत पूरी तरह मान्य नहीं है और देखा जाए तो मानव गतिविधियों के कारण ग्लोबल वार्मिंग के प्रभावों में तेजी से जलवायु परिवर्तन तेज हो गया है. अनेक पर्यावरणविदों और वैज्ञानिकों ने आशंका जताई है कि ग्लोबल वॉर्मिंग के चलते हो रहा जलवायु परिवर्तन निकट भविष्य में कई प्रजातियों के विलुप्त होने का सबसे बड़ा कारण हो सकता है.
जलवायु परिवर्तन का सबसे दूरगामी प्रभाव पड़ता है उस क्षेत्र में रहने वाली प्रजातियों पर. तापमान के कुछ डिग्री सेंटीग्रेट ऊपर नीचे होने भर से कई प्रजातियां के विलुप्तीकरण का खतरा पैदा हो जाता है. ग्लोबल वॉर्मिंग के प्रभावों का सबसे ज्यादा दुष्प्रभाव पड़ता है क्षेत्र के स्थानीय पारिस्थितिक तंत्र पर, जो बहुत ही नाजुक होते हैं.
ध्रुवीय भालू पर ग्लोबल वॉर्मिंग की सीधी मार
एक ओवरहीटिंग जलवायु वैश्विक परिस्थितियों में कितना बड़ा परिवर्तन पैदा कर रही है और मौजूदा नाजुक पारिस्थितिकी प्रणालियों में वर्तमान प्रजातियों को कितना नुकसान हो सकता है, नीचे दिए गए कुछ उदाहरणों से समझा जा सकता हैः
उत्तरी गोलार्द्ध में स्थित कनाडा के बर्फीले मैदानों से ध्रुवीय भालू गायब होते जा रहे है, क्योंकि कनाडा में बर्फीला क्षेत्र लगातार कम होता जा रहा है. ध्रुवीय भालुओं के प्राकृतिक रहवास में बर्फ उनकी खाद्य श्रृंखला के लिए सबसे ज्यादा महत्वपूर्ण तत्व है. आर्कटिक समुद्र में भालू शिकार के लिए सिर्फ बर्फ पर निर्भर हैं. यह जीव खुले समुद्र में सील व मछलियों का शिकार करते समय बर्फ को एक अस्थायी मंच के रूप में उपयोग करता है.
विशेषज्ञों का मानना है कि आर्कटिक समुद्र में बर्फ प्रति दशक 9 प्रतिशत की दर से पिघल रही है. यह समुद्र ही ध्रुवीय भालू का एकमात्र निवास स्थान है, जहां उनके अस्तित्व पर खतरा छा गया है.
दक्षिण अमेरिका में सालाना प्रजनन के लिए समुद्री कछुए ब्राजील के समुद्र तटों पर अपने अंडे देने आते हैं, तटों की नरम रेत पर घोंसले बनाने की सबसे बड़ी वजह है वहां का मुफीद तापमान. रेत का तापमान कछुओं के अंडों का लिंग निर्धारण करता है. ठंडी रेत से मादा कछुए और अगर रेत गरम हो तो नर कछुए अंडों से बाहर आते हैं और इस संतुलन से वंशवृद्धि निश्चित होती है.
लेकिन ग्लोबल वॉर्मिंग से समुद्र का स्तर बढ़ने लगा है और अलग-अलग स्थानों पर दिए गए अंडों के पानी में डूबने का खतरा बना हुआ है. ग्लोबल वॉर्मिंग के
पिघल रहे हैं ग्लेशियर कारण पानी का तापमान भी अनिश्चित हो गया है. इससे रेत के तापमान में घट-बढ़ से अंडों से सभी मादा या नर कछुए पैदा होने का डर है, जिससे इस प्रजाति का प्राकृतिक संतुलन बिगड़ रहा है.
उत्तरी अटलांटिक के सबसे बड़े और शानदार प्राणी व्हेल से मानव द्वारा शोषण का एक लंबा इतिहास जुड़ा है, लेकिन अब समुद्र के पानी के तापमान में वृद्धि के कारण व्हेल का आहार प्रभावित हो रहा है.
प्लांक्टन और कवक पर आश्रित व्हेल को अब खाने की तलाश में काफी दिक्कतें आ रही हैं. ग्लोबल वॉर्मिंग के चलते पानी का तापमान बदला है, जिससे प्लांक्टन और कवक की संख्या में अप्रत्याशित कमी देखी गई है.
चीन के विशाल पांडा का भविष्य अनिश्चित बना हुआ है. इसके आवास दक्षिण पश्चिमी चीन के पहाड़ी क्षेत्रों में पाए जाने वाले बांस के वन अब खंडित हो चुके हैं. विशाल पांडा की आबादी अब नगण्य है और इनका मुख्य आहार बांस है. चीन के बांस के जंगल एक नाजुक पारिस्थितिकी तंत्र है और ग्लोबल वार्मिंग के कारण जलवायु परिवर्तन से प्रभावित हैं
महामशीन का पहला महाप्रयोग
: दोष ईश्वर का ही है जो कहते हैं कि कण कण में बसे हैं. इसीलिए सबसे सूक्ष्म भौतिक कण में सबसे विराट आध्यात्मिक शक्ति खोजी जा रही है. उस कण को कहते तो हैं हिग्स-बोसोन, पर मानते हैं कि वही "ब्रह्मकण" है.
मंगलवार 30 मार्च से जेनेवा के पास यूरोपीय मूलकण प्रयोगशाला सेर्न में हिग्स-बोसोन के अस्तित्व का खंडन या मंडन करने के महाप्रयोग का पहला अपूर्व प्रयास शुरू हुआ, हालांकि शुरू होते ही मूलकण त्वरक एलएचसी की सुरक्षा प्रणाली ने दो बार प्रयोग को रोक भी दिया. बताया गया कि मशीन की बिजली की प्रणाली में किसी गड़बड़ी के कारण सुरक्षा प्रणाली ने अपने आप प्रयोग को रोक दिया. लेकिन तीसरा प्रयास सफल रहा. दो प्रोटोन किरणों की आपस में टक्कर हुई. यह अभी नहीं कहा जा सकता कि इस टक्कर से ब्रह्मकण हिग्स-बोसोन बने या नहीं.
प्रयोग से पहले सभी वैज्ञानिक बहुत उत्साहित और उत्तेजित थे. सेर्न के महानिदेशक, जर्मनी के रोल्फ़-डीटर होयर ने कहा, "हिग्स का अस्तित्व यदि सचमुच है, तो एलएचसी उसे पा कर ही रहेगा."
एलएचसी (लार्ज हैड्रन कोलाइडर) नाम है उस महामशीन का, जिस के 27 किलोमीटर लंबे निर्वात पाइपों में प्रोटोन कणों को पहले त्वरित किया जाता है. जब उनकी गति प्रकाश की गति (तीन लाख किलोमीटर प्रतिसेकंड) से कुछ ही कम रह जाएगी, तब दो विपरीत दिशाओं से आते हुए कणों की आपस में टक्कर कराई जाएगी.
समझा जाता है कि इस टक्कर से एक बहुत ही सूक्ष्म पैमाने पर लगभग वही परिस्थिति पैदा होगी, जो 13 अरब 70 करोड़ साल पहले उस समय थी, जब एक महाधमाके (बिग बैंग) के साथ ब्रह्मांड की उत्पत्ति हुई थी. ब्रह्मांड की उत्पत्ति के समय सबसे पहले हिग्स-बोसोन ही बने होंगे. उन से बाद में बने वे अन्य कण, जिन से अणु और परमाणु बने होते हैं. इस चराचर जगत में हर जीव-निर्जीव इलेक्ट्रोन, प्रोटोन, न्यूट्रोन वाले परमाणुओं का ही बना है.
30 मार्च से शुरू हो रहे प्रयोग में वैज्ञानिक प्रोटोन कणों की दो विपरीत दिशाओं से आ रही किरणों की गति बढ़ाने के लिए हर किरण को साढ़े तीन टेरा यानी साढ़े तीन खरब इलेक्ट्रॉनवोल्ट तक की ऊर्जा प्रदान करेंगे. यह अब तक का एक नया रेकॉर्ड होगा, हालांकि एलएचसी की क्षमता हर किरण को सात टेरा इलेक्ट्रॉन वोल्ट तक की त्वरण ऊर्जा प्रदान करने की है.
सितंबर 2008 में जब एलएचसी पहली बार चालू हुआ था, तब सारी दुनिया में कोहराम मच गया था कि जेनेवा में एक ऐसा प्रयोग होने जा रहा है, जिससे ऐसे ब्लैक होल (कृष्ण विवर) बन सकते हैं, जो धरती सहित सब कुछ निगल सकते हैं. उस समय, कुछ ही दिन बाद बिजली के एक शॉर्ट सर्किट के कारण एलएचसी को बंद कर देना पड़ा.
सेर्न के महानिदेशक रोल्फ़-डीटर होयर ने जर्मनी के डोएचलांड रेडियो के साथ एक भेंटवार्ता में सोमवार को कहा कि बहुत हुआ तो ऐसे अतिसूक्ष्म ब्लैक होल बन सकते हैं, जो वास्तव में पदार्थ की हमारे लिए अपरिचित क्वांटम अवस्थाएं हो सकते हैं. क्वांटम अवस्था उस अवस्था को कहा जा सकता है, जिस में पदार्थ और ऊर्जा के बीच का द्वैत अद्वैत में बदल जाता है. लेकिन यह अद्वैत रूप भी इतना क्षणिक होगा कि वह तुरंत विघटित हो कर द्वैत में बदल जायेगा. होयर ने कहा कि हमारे ब्रह्मांड में अरबों वर्षों से हर सेकेंड अरबों-खरबों इस तरह की प्रघटनाएं हो रही हैं "और हम अब भी हैं."
हिग्स-बोसोन अभी तक दो वैज्ञानिकों ब्रिटेन के पीटर हिग्स और भारत के सत्येंद्रनाथ बोस की ऐसी कल्पना हैं, जिन के बारे में माना जाता है कि वे ही प्रटोन और न्यूट्रोन कणों को उनका भार देते हैं. पदार्थ, अर्थात अणु-परमाणु की संरचना संबंधी इस समय का तथाकथित स्टैंडर्ड मॉडल यदि सही है, तो हिग्स-बोसोन का भी अस्तित्व होना चाहिए.
पदार्थ और कुछ नहीं, ऊर्जा का ही दूसरा रूप है. लेकिन, ऊर्जा का कोई द्रव्यमान (भार) नहीं होता, जबकि पदार्थ का होता है. अतः प्रश्न यही उठता है कि यह द्रव्यमान कहां से आता है, कैसे आता है?
सेर्न के महानिदेशक होयर ने यह भी कहा कि एलएचसी में दो प्रोटोन किरणों की टक्कर कुछ वैसी ही है, "मानो एटलांटिक महासागर के ऊपर दो सूइयां आपस में टकराएं." सेर्न की ओर से बताया गया है कि पहली टक्कर होने तक कई दिन बीत सकते हैं. उस के बाद भी टक्कर के आंकड़ों की जांच-परख करने और उनमें हिग्स-बोसोन के संकेत पहचानने में महीनों लग सकते हैं, क्योंकि सिद्धांततः अरबों टक्करों में से केवल कोई एक टक्कर ऐसी हो सकती है, जिसमें हो सकता है कि बहुत ही अल्प समय के लिए हिग्स-बोसोन बने हों. यह ब्रह्मांड के अरबों-खरबों पिंडों के बीच किसी ऐसे पिंड की तलाश करने जैसा है, जहां हमारी पृथ्वी जैसी कोई दुनिया भी बसी हो.
संसार की सबसे मंहगी महामशीन एलएचसी एक साल चली मरम्मत के बाद नंवबर से दुबारा काम करने लायक बनी है. सर्दियों के अवकाश के बाद फ़रवरी के अंत में उसे फिर से चालू किया गया. नई मरम्मतों के लिए अगले वर्ष उसे फिर से बंद कर दिया जाएगा.
मंगलवार 30 मार्च से जेनेवा के पास यूरोपीय मूलकण प्रयोगशाला सेर्न में हिग्स-बोसोन के अस्तित्व का खंडन या मंडन करने के महाप्रयोग का पहला अपूर्व प्रयास शुरू हुआ, हालांकि शुरू होते ही मूलकण त्वरक एलएचसी की सुरक्षा प्रणाली ने दो बार प्रयोग को रोक भी दिया. बताया गया कि मशीन की बिजली की प्रणाली में किसी गड़बड़ी के कारण सुरक्षा प्रणाली ने अपने आप प्रयोग को रोक दिया. लेकिन तीसरा प्रयास सफल रहा. दो प्रोटोन किरणों की आपस में टक्कर हुई. यह अभी नहीं कहा जा सकता कि इस टक्कर से ब्रह्मकण हिग्स-बोसोन बने या नहीं.
प्रयोग से पहले सभी वैज्ञानिक बहुत उत्साहित और उत्तेजित थे. सेर्न के महानिदेशक, जर्मनी के रोल्फ़-डीटर होयर ने कहा, "हिग्स का अस्तित्व यदि सचमुच है, तो एलएचसी उसे पा कर ही रहेगा."
एलएचसी (लार्ज हैड्रन कोलाइडर) नाम है उस महामशीन का, जिस के 27 किलोमीटर लंबे निर्वात पाइपों में प्रोटोन कणों को पहले त्वरित किया जाता है. जब उनकी गति प्रकाश की गति (तीन लाख किलोमीटर प्रतिसेकंड) से कुछ ही कम रह जाएगी, तब दो विपरीत दिशाओं से आते हुए कणों की आपस में टक्कर कराई जाएगी.
समझा जाता है कि इस टक्कर से एक बहुत ही सूक्ष्म पैमाने पर लगभग वही परिस्थिति पैदा होगी, जो 13 अरब 70 करोड़ साल पहले उस समय थी, जब एक महाधमाके (बिग बैंग) के साथ ब्रह्मांड की उत्पत्ति हुई थी. ब्रह्मांड की उत्पत्ति के समय सबसे पहले हिग्स-बोसोन ही बने होंगे. उन से बाद में बने वे अन्य कण, जिन से अणु और परमाणु बने होते हैं. इस चराचर जगत में हर जीव-निर्जीव इलेक्ट्रोन, प्रोटोन, न्यूट्रोन वाले परमाणुओं का ही बना है.
30 मार्च से शुरू हो रहे प्रयोग में वैज्ञानिक प्रोटोन कणों की दो विपरीत दिशाओं से आ रही किरणों की गति बढ़ाने के लिए हर किरण को साढ़े तीन टेरा यानी साढ़े तीन खरब इलेक्ट्रॉनवोल्ट तक की ऊर्जा प्रदान करेंगे. यह अब तक का एक नया रेकॉर्ड होगा, हालांकि एलएचसी की क्षमता हर किरण को सात टेरा इलेक्ट्रॉन वोल्ट तक की त्वरण ऊर्जा प्रदान करने की है.
सितंबर 2008 में जब एलएचसी पहली बार चालू हुआ था, तब सारी दुनिया में कोहराम मच गया था कि जेनेवा में एक ऐसा प्रयोग होने जा रहा है, जिससे ऐसे ब्लैक होल (कृष्ण विवर) बन सकते हैं, जो धरती सहित सब कुछ निगल सकते हैं. उस समय, कुछ ही दिन बाद बिजली के एक शॉर्ट सर्किट के कारण एलएचसी को बंद कर देना पड़ा.
सेर्न के महानिदेशक रोल्फ़-डीटर होयर ने जर्मनी के डोएचलांड रेडियो के साथ एक भेंटवार्ता में सोमवार को कहा कि बहुत हुआ तो ऐसे अतिसूक्ष्म ब्लैक होल बन सकते हैं, जो वास्तव में पदार्थ की हमारे लिए अपरिचित क्वांटम अवस्थाएं हो सकते हैं. क्वांटम अवस्था उस अवस्था को कहा जा सकता है, जिस में पदार्थ और ऊर्जा के बीच का द्वैत अद्वैत में बदल जाता है. लेकिन यह अद्वैत रूप भी इतना क्षणिक होगा कि वह तुरंत विघटित हो कर द्वैत में बदल जायेगा. होयर ने कहा कि हमारे ब्रह्मांड में अरबों वर्षों से हर सेकेंड अरबों-खरबों इस तरह की प्रघटनाएं हो रही हैं "और हम अब भी हैं."
हिग्स-बोसोन अभी तक दो वैज्ञानिकों ब्रिटेन के पीटर हिग्स और भारत के सत्येंद्रनाथ बोस की ऐसी कल्पना हैं, जिन के बारे में माना जाता है कि वे ही प्रटोन और न्यूट्रोन कणों को उनका भार देते हैं. पदार्थ, अर्थात अणु-परमाणु की संरचना संबंधी इस समय का तथाकथित स्टैंडर्ड मॉडल यदि सही है, तो हिग्स-बोसोन का भी अस्तित्व होना चाहिए.
पदार्थ और कुछ नहीं, ऊर्जा का ही दूसरा रूप है. लेकिन, ऊर्जा का कोई द्रव्यमान (भार) नहीं होता, जबकि पदार्थ का होता है. अतः प्रश्न यही उठता है कि यह द्रव्यमान कहां से आता है, कैसे आता है?
सेर्न के महानिदेशक होयर ने यह भी कहा कि एलएचसी में दो प्रोटोन किरणों की टक्कर कुछ वैसी ही है, "मानो एटलांटिक महासागर के ऊपर दो सूइयां आपस में टकराएं." सेर्न की ओर से बताया गया है कि पहली टक्कर होने तक कई दिन बीत सकते हैं. उस के बाद भी टक्कर के आंकड़ों की जांच-परख करने और उनमें हिग्स-बोसोन के संकेत पहचानने में महीनों लग सकते हैं, क्योंकि सिद्धांततः अरबों टक्करों में से केवल कोई एक टक्कर ऐसी हो सकती है, जिसमें हो सकता है कि बहुत ही अल्प समय के लिए हिग्स-बोसोन बने हों. यह ब्रह्मांड के अरबों-खरबों पिंडों के बीच किसी ऐसे पिंड की तलाश करने जैसा है, जहां हमारी पृथ्वी जैसी कोई दुनिया भी बसी हो.
संसार की सबसे मंहगी महामशीन एलएचसी एक साल चली मरम्मत के बाद नंवबर से दुबारा काम करने लायक बनी है. सर्दियों के अवकाश के बाद फ़रवरी के अंत में उसे फिर से चालू किया गया. नई मरम्मतों के लिए अगले वर्ष उसे फिर से बंद कर दिया जाएगा.
खिलाड़ियों को फंसाने वाली बीमारी
खिलाड़ियों को फंसाने वाली बीमारी
: क्लाउडिया पेषश्टाइन डोपिंग किसी भी खिलाड़ी के करियर को तबाह कर सकता है. लेकिन जर्मनी की क्लाउडिया पेषश्टाइन कोई प्रतिबंधित दवा लिए बिना ही डोपिंग में पकड़ी गई और उन पर प्रतिबंध भी लगा. दरअसल उन्हें खून की एक वंशानुगत बीमारी है.
आइस स्कैटिंग करने वाली जर्मन एथलीट क्लाउडिया पेषश्टाइन के करियर में तब अचानक से ब्रेक लग गया जब उन्हें अप्रत्यक्ष डोपिंग के आरोप में खेलने से रोक दिया गया. अप्रत्यक्ष डोपिंग का मतलब है कि खिलाड़ी किसी बीमारी के लिए दवा ले रहा है लेकिन उसका असर ऐसा होता है, जैसे उसने प्रतिबंधित दवाएं ले ली हों. क्लाउडिया बार बार कहती रहीं कि उन्होंने डोपिंग नहीं किया है लेकिन उनके ख़ून में बराबर एक केमिकल की मात्रा ज़्यादा आ रही थी.
37 साल की क्लाउडिया को इन सब आरोपों से थोड़ी राहत तब मिली जब डॉक्टर ने कहा कि उसे एक वंशानुगत बीमारी है जिसकी वजह से उसके ख़ून में गड़बड़ी है. डॉक्टर गेरहार्ड एहनिंगर बताते हैं कि क्लाउडिया के ख़ून में लगातार रेटिक्युलोज़ाइटन की मात्रा ज़्यादा आ रही थी. यूरोप में ख़ून की जांच करने वाली लैबोरेटरी के प्रमुख डॉक्टर आन्द्रियास वाइमान कहते हैं, "जैसा कि हमने पाया कि क्लाउडिया के ख़ून में अनियमितताओं का कारण पिता से आई बीमारी है. उससे भी आश्चर्य की बात ये है कि उसके किसी भी भाई बहन को यह बीमारी नहीं है."
: शानदार करियर पर ग्रहण
बर्लिन की रहने वाली इस आइस स्केटर की बीमारी ख़ून में एक तरह की अनियमितता है जिसे डॉक्टर स्फेरोसायटोसिस कहते हैं. जर्मनी में आठ लाख लोगों में यह गड़बड़ी वाला जीन होता है. हालांकि इससे जीवन को कोई ख़तरा नहीं होता. खिलाड़ियों की क्षमता में भी कोई समस्या नहीं होती, बस डोपिंग की टेस्ट में पता नहीं होने पर गड़बड़ी हो जाती है. वैसे भी डायरेक्ट डोपिंग के मामले में अभी तक क्लाउडिया पेषश्टाइन को नहीं पकड़ा गया है लेकिन फिर भी नियमों के हिसाब से उस पर प्रतिबंध तो लग ही गया है.
वहीं ल्यूबिक की यूनिवर्सिटी में फिजियोलॉजी संस्थान के प्रमुख वोल्फ़गांग येल्केमान ने उम्मीद नहीं छोड़ी है. वह कहते हैं, "मुझे विश्वास है कि अगर इस केस को फिर से देखा जाए तो बहुत संभव है कि नए लेबोरेट्री नमूनों से अभी का फ़ैसला बदला जा सकेगा. अप्रत्यक्ष डोपिंग के मामले में भी इन नमूनों का फ़ायदा होगा."
लेकिन जब तक ये सब कुछ होगा क्या क्लाउडिया पेषश्टाइन का करियर बच पाएगा!
: क्लाउडिया पेषश्टाइन डोपिंग किसी भी खिलाड़ी के करियर को तबाह कर सकता है. लेकिन जर्मनी की क्लाउडिया पेषश्टाइन कोई प्रतिबंधित दवा लिए बिना ही डोपिंग में पकड़ी गई और उन पर प्रतिबंध भी लगा. दरअसल उन्हें खून की एक वंशानुगत बीमारी है.
आइस स्कैटिंग करने वाली जर्मन एथलीट क्लाउडिया पेषश्टाइन के करियर में तब अचानक से ब्रेक लग गया जब उन्हें अप्रत्यक्ष डोपिंग के आरोप में खेलने से रोक दिया गया. अप्रत्यक्ष डोपिंग का मतलब है कि खिलाड़ी किसी बीमारी के लिए दवा ले रहा है लेकिन उसका असर ऐसा होता है, जैसे उसने प्रतिबंधित दवाएं ले ली हों. क्लाउडिया बार बार कहती रहीं कि उन्होंने डोपिंग नहीं किया है लेकिन उनके ख़ून में बराबर एक केमिकल की मात्रा ज़्यादा आ रही थी.
37 साल की क्लाउडिया को इन सब आरोपों से थोड़ी राहत तब मिली जब डॉक्टर ने कहा कि उसे एक वंशानुगत बीमारी है जिसकी वजह से उसके ख़ून में गड़बड़ी है. डॉक्टर गेरहार्ड एहनिंगर बताते हैं कि क्लाउडिया के ख़ून में लगातार रेटिक्युलोज़ाइटन की मात्रा ज़्यादा आ रही थी. यूरोप में ख़ून की जांच करने वाली लैबोरेटरी के प्रमुख डॉक्टर आन्द्रियास वाइमान कहते हैं, "जैसा कि हमने पाया कि क्लाउडिया के ख़ून में अनियमितताओं का कारण पिता से आई बीमारी है. उससे भी आश्चर्य की बात ये है कि उसके किसी भी भाई बहन को यह बीमारी नहीं है."
: शानदार करियर पर ग्रहण
बर्लिन की रहने वाली इस आइस स्केटर की बीमारी ख़ून में एक तरह की अनियमितता है जिसे डॉक्टर स्फेरोसायटोसिस कहते हैं. जर्मनी में आठ लाख लोगों में यह गड़बड़ी वाला जीन होता है. हालांकि इससे जीवन को कोई ख़तरा नहीं होता. खिलाड़ियों की क्षमता में भी कोई समस्या नहीं होती, बस डोपिंग की टेस्ट में पता नहीं होने पर गड़बड़ी हो जाती है. वैसे भी डायरेक्ट डोपिंग के मामले में अभी तक क्लाउडिया पेषश्टाइन को नहीं पकड़ा गया है लेकिन फिर भी नियमों के हिसाब से उस पर प्रतिबंध तो लग ही गया है.
वहीं ल्यूबिक की यूनिवर्सिटी में फिजियोलॉजी संस्थान के प्रमुख वोल्फ़गांग येल्केमान ने उम्मीद नहीं छोड़ी है. वह कहते हैं, "मुझे विश्वास है कि अगर इस केस को फिर से देखा जाए तो बहुत संभव है कि नए लेबोरेट्री नमूनों से अभी का फ़ैसला बदला जा सकेगा. अप्रत्यक्ष डोपिंग के मामले में भी इन नमूनों का फ़ायदा होगा."
लेकिन जब तक ये सब कुछ होगा क्या क्लाउडिया पेषश्टाइन का करियर बच पाएगा!
हमारे बीच ही रहते हैं एलियंस!
एलियंस यानी दूसरे गृह के प्राणियों के बारे में आप का क्या ख़याल है? एक सर्वेक्षण के मुताबिक विश्व में 20 प्रतिशत लोगों का मानना है कि एलियंस हमारे बीच इंसानों के भेष में घूमते हैं.
समाचार एजेंसी रॉयटर्स ने एक सर्वेक्षण किया जिसमें 22 देशों के 23 हजार लोगों से सवाल पूछे गए. भारत और चीन में 40 प्रतिशत से ज़्यादा लोगों का मानना है कि एलियंस पृथ्वी पर मनुष्यों के भेष में घूमते हैं. वहीं नीदरलैंड्स, स्वीडेन और बेल्जियम के ज़्यादातर लोग ऐसा नहीं मानते. वहां केवल 8 प्रतिशत लोग ही एलियंस की उपस्थिति पर विश्वास करते हैं.
सर्वेक्षण में हिस्सा लेने वाले लोगों में से 80 प्रतिशत को पक्का भरोसा है कि एलियंस हमारे बीच नहीं रहते हैं. इपसोस मार्केट रिसर्च कंपनी के अधिकारी जॉन राइट का कहना है, "अगर सर्वेक्षण के परिणामों को देखा जाए तो जिन देशों की जनसंख्या ज़्यादा है, वहां ज़्यादा लोगों का मानना है कि एलियंस हमारे बीच हैं लेकिन छोटी जनसंख्या वाले देशों में कम लोग ही ऐसा समझते हैं. हो सकता है कि एक छोटे देश में आप अपने पड़ोसी को ज़्यादा अच्छी तरह जानते हों."
ज़्यादातर महिलाएं पड़ोसियों के हालचाल और सामाजिक मेल मिलाप में विश्वास रखती हैं. शायद इसलिए 17 प्रतिशत महिलाओं के मुकाबले 22 प्रतिशत परुष इस बात को मानते हैं कि हमारे आसपास आदमियों के भेष में एलियन रहते हैं. इस बात पर विश्वास करने वाले ज़्यादातर लोगों की उम्र 35 साल से कम है जबकि ऐसा न मानने वालों में ज़्यादा संख्या महिलाओं की है.
समाचार एजेंसी रॉयटर्स ने एक सर्वेक्षण किया जिसमें 22 देशों के 23 हजार लोगों से सवाल पूछे गए. भारत और चीन में 40 प्रतिशत से ज़्यादा लोगों का मानना है कि एलियंस पृथ्वी पर मनुष्यों के भेष में घूमते हैं. वहीं नीदरलैंड्स, स्वीडेन और बेल्जियम के ज़्यादातर लोग ऐसा नहीं मानते. वहां केवल 8 प्रतिशत लोग ही एलियंस की उपस्थिति पर विश्वास करते हैं.
सर्वेक्षण में हिस्सा लेने वाले लोगों में से 80 प्रतिशत को पक्का भरोसा है कि एलियंस हमारे बीच नहीं रहते हैं. इपसोस मार्केट रिसर्च कंपनी के अधिकारी जॉन राइट का कहना है, "अगर सर्वेक्षण के परिणामों को देखा जाए तो जिन देशों की जनसंख्या ज़्यादा है, वहां ज़्यादा लोगों का मानना है कि एलियंस हमारे बीच हैं लेकिन छोटी जनसंख्या वाले देशों में कम लोग ही ऐसा समझते हैं. हो सकता है कि एक छोटे देश में आप अपने पड़ोसी को ज़्यादा अच्छी तरह जानते हों."
ज़्यादातर महिलाएं पड़ोसियों के हालचाल और सामाजिक मेल मिलाप में विश्वास रखती हैं. शायद इसलिए 17 प्रतिशत महिलाओं के मुकाबले 22 प्रतिशत परुष इस बात को मानते हैं कि हमारे आसपास आदमियों के भेष में एलियन रहते हैं. इस बात पर विश्वास करने वाले ज़्यादातर लोगों की उम्र 35 साल से कम है जबकि ऐसा न मानने वालों में ज़्यादा संख्या महिलाओं की है.
चीनी जहाज से समंदर में बड़े प्रदूषण का खतरा
चीनी जहाज से समंदर में बड़े प्रदूषण का खतरा
ऑस्ट्रेलिया के ग्रेट बैरियर रीफ से गुज़र रहे चीन के एक जहाज़ के दुर्घटनाग्रस्त हो जाने से समंदर में प्रदूषण और वहां रहने वाली मूंगों की बेशुमार प्रजातियों के लिए खतरा पैदा हो गया है. जहाज से रिसते तेल ने बढाई चिंता.
रीफ़ मूंगों जैसे समुद्री जीवों के जुड़ने से बने छोटे द्वीपों को कहते हैं. ग्रेट बैरियर रीफ़ दुनिया की सबसे बड़ा रीफ़ इलाका है और इसमें लगभग 2900 रीफ़ और 900 द्वीप शामिल हैं. समदंर के बहुत से प्राणी रीफ़ को अपना घर बनाते हैं. ग्रेट बैरियर रीफ़ को संयुक्त राष्ट्र ने विश्व धरोहर का दर्जा दिया है.
शेंग नेंग 1 नाम का चीनी जहाज़ रीफ़ से शनिवार को टकराया और ज़मीन पर चढ़ गया जिससे उसके टैंकर में छेद हो गए और तेल रिसने लगा. ऑस्ट्रेलिया के राज्य क्वीन्सलैंड की मुख्यमंत्री एना ब्लाई ने कहा कि जहाज़ को सहारा देने के लिए दोनों तरफ जहाज़ों को तैनात किया गया और शेग नेंग 1 से तेल दूसरे जहाज़ में लाने की बात चल रही है.
चीनी जहाज से रिसते तेल की वजह से इस जैव धरोहर को खतरा पैदा हो गया है. इस जहाज पर 65 हजार टन कोयला लदा है. साथ ही इसमें 950 टन कच्चा तेल भी मौजूद है. इस सामान को दूसरे जहाजों पर लादने में हफ्तों और महीनों का समय लग सकता है.
अब तक शेंग नेंग 1 से ढाई टन तेल बाहर सागर रिस चुका है और समंदर पर तीन किलोमीटर दूर तक तेल की परत बन गई है. ऑस्ट्रेलिया के सागर सुरक्षा प्राधिकरण के प्रवक्ता ग्रैहम पीची का कहना है कि इस वक़्त सबसे ज़रूरी है कि रीफ को तेल के प्रदूषण से बचाया जाए. ग्रेट बैरियर रीफ के आसपास के इलाकों में कई समुद्री जीव पाए जाते हैं. पीची के मुताबिक इसकी रक्षा के लिए ख़ास क़ानून भी बनाए गए हैं.
सुरक्षा अधिकारी पैट्रिक क्वर्क का कहना है कि जहाज़ बार बार रीफ से टकरा रहा है जिससे उसके मूल ढांचे को नुकसान पहुंच सकता है. ब्लाई के मुताबिक चीनी जहाज ग़ैर क़ानूनी तरीके से बैरियर रीफ के इन इलाकों तक पहुंचा है. ऑस्ट्रेलिया की सरकार इसकी जांच रही है और ब्लाई को उम्मीद है कि शेंग नेंग 1 पर कोई कार्रवाई भी होगी.
By.-Susheel Dwivedi
Kendriya Vidyalaya Dholchera
Assam
www.bioguruindia.blogspot.com
ऑस्ट्रेलिया के ग्रेट बैरियर रीफ से गुज़र रहे चीन के एक जहाज़ के दुर्घटनाग्रस्त हो जाने से समंदर में प्रदूषण और वहां रहने वाली मूंगों की बेशुमार प्रजातियों के लिए खतरा पैदा हो गया है. जहाज से रिसते तेल ने बढाई चिंता.
रीफ़ मूंगों जैसे समुद्री जीवों के जुड़ने से बने छोटे द्वीपों को कहते हैं. ग्रेट बैरियर रीफ़ दुनिया की सबसे बड़ा रीफ़ इलाका है और इसमें लगभग 2900 रीफ़ और 900 द्वीप शामिल हैं. समदंर के बहुत से प्राणी रीफ़ को अपना घर बनाते हैं. ग्रेट बैरियर रीफ़ को संयुक्त राष्ट्र ने विश्व धरोहर का दर्जा दिया है.
शेंग नेंग 1 नाम का चीनी जहाज़ रीफ़ से शनिवार को टकराया और ज़मीन पर चढ़ गया जिससे उसके टैंकर में छेद हो गए और तेल रिसने लगा. ऑस्ट्रेलिया के राज्य क्वीन्सलैंड की मुख्यमंत्री एना ब्लाई ने कहा कि जहाज़ को सहारा देने के लिए दोनों तरफ जहाज़ों को तैनात किया गया और शेग नेंग 1 से तेल दूसरे जहाज़ में लाने की बात चल रही है.
चीनी जहाज से रिसते तेल की वजह से इस जैव धरोहर को खतरा पैदा हो गया है. इस जहाज पर 65 हजार टन कोयला लदा है. साथ ही इसमें 950 टन कच्चा तेल भी मौजूद है. इस सामान को दूसरे जहाजों पर लादने में हफ्तों और महीनों का समय लग सकता है.
अब तक शेंग नेंग 1 से ढाई टन तेल बाहर सागर रिस चुका है और समंदर पर तीन किलोमीटर दूर तक तेल की परत बन गई है. ऑस्ट्रेलिया के सागर सुरक्षा प्राधिकरण के प्रवक्ता ग्रैहम पीची का कहना है कि इस वक़्त सबसे ज़रूरी है कि रीफ को तेल के प्रदूषण से बचाया जाए. ग्रेट बैरियर रीफ के आसपास के इलाकों में कई समुद्री जीव पाए जाते हैं. पीची के मुताबिक इसकी रक्षा के लिए ख़ास क़ानून भी बनाए गए हैं.
सुरक्षा अधिकारी पैट्रिक क्वर्क का कहना है कि जहाज़ बार बार रीफ से टकरा रहा है जिससे उसके मूल ढांचे को नुकसान पहुंच सकता है. ब्लाई के मुताबिक चीनी जहाज ग़ैर क़ानूनी तरीके से बैरियर रीफ के इन इलाकों तक पहुंचा है. ऑस्ट्रेलिया की सरकार इसकी जांच रही है और ब्लाई को उम्मीद है कि शेंग नेंग 1 पर कोई कार्रवाई भी होगी.
By.-Susheel Dwivedi
Kendriya Vidyalaya Dholchera
Assam
www.bioguruindia.blogspot.com
बड़बोला भगवानः क्रेग वेंटर
जीनोम से भी जटिल है जीवन
बड़बोला भगवानः क्रेग वेंटर
दस साल पहले अमेरिकी वैज्ञानिक क्रेग वेन्टर ने बड़े गर्व से घोषणा की थी कि उनकी प्रयोगशाला सेलेरा जीनोमिक्स में मानवीय जीनोम के अधिकांश जीनों को पढ़ लिया गया है. लेकिन जीवन की जटिलता को सामने आने में अभी और वक्त लगेगा.
क्रेग वेन्टर को गर्व इस बात का भी था कि सरकारी सहायताओं से चल रहा अंतरराष्ट्रीय ह्यूमन जीनोम प्रॉजेक्ट इस काम में पिछड़ गया था. उनकी घोषणा से दोनों के बीच प्रतियोगिता और भी तेज़ हो गई. लेकिन जून 2000 में दोनों ने मिल कर मानवीय जीनोम का एक आरंभिक नक्शा पेश किया. उस समय वेंटर ने कहा, "मैंने दूसरे लोगों की टीका टिप्णियों की कभी परवाह नहीं की. मैं मेहनत से काम करता हूं. अधिक से अधिक जानकारियां जुटाता हूं और अपनी राय आप बनाता हूं.
इस बीच अनुवंशिक जीवविज्ञान में बहुत प्रगति हुई है. मानवीय जीनभंडार यानी जीनोम को विकोडित कर लेने से सारी बीमारियों पर विजय पा लेने का सब्ज़बाग हालांकि अब भी टेढ़ी खीर है, तब भी यह तो मानना ही पड़ेगा कि मनमौज़ी क्रेग वेंटर के भड़काऊ कामों ने इस क्षेत्र में एक क्रांति-सी ला दी है. वह कहते हैं, "ऐसे भी लोग होते हैं, जो हाई स्कूल से आते ही अपना विचार बना चुके होते हैं. वे जानते हैं कि उन्हें क्या करना है और वे अपना विचार कभी बदलते नहीं. मैं अब भी जानने में लगा हूं कि मैं अभी और क्या कुछ कर सकता हूं."
बड़बोली बातें
वेंटर का बड़बोलापन कड़वा भले ही लगे, लेकिन वह अपना काम कर जाता है. 1998 में उन्होंने मानवीय जीनों की कोड भाषा को पढ़ कर उनका नक्शा बनाने के लिए सेलेरा जीनोमिक्स की स्थापना की. हालांकि इसी काम के लिए ह्यूमन जीनोम प्रॉजेक्ट नाम से एक अंतरराष्ट्रीय परियोजना 1990 से ही चल रही थी. वेंटर ने अपनी निजी प्रयोगशाला में यह काम सरकारी पैसों से चल रही अंतरराष्ट्रीय परियोजना से पहले ही लगभग पूरा कर लिया.
अंतरराष्ट्रीय परियोजना में काम कर रहे वैज्ञानिकों की सुस्ती पर कटाक्ष करते हुए वेंटर कहते हैं, "मैं भी यदि उनकी तरह समझौतावादी और सुस्त रहा होता, तो मानवीय जीनोम आज तक पढ़ा नहीं जा सका होता."
भगवान बनने का दंभ
63 वर्ष के वेंटर कहीं न कहीं भगवान बनने और दुनिया को कुछ देकर जाने के उत्कट अभिलाषी लगते हैं. तभी तो वह कहते हैं, "हो सकता है कि मेरी बात साइंस फ़िक्शन जैसी लगे, लेकिन योजना और आनुवंशिक चयन एक दिन डार्विन के विकासवाद का स्थान ले लेंगे."
वेंटर अपने विज्ञान के लिए नैतिकता की कोई सीमारेखा स्वीकार नहीं करते. उनकी अगली ज़िद है मनुष्य का बनाया कृत्रिम जीवन पैदा करना. 2007 में उन्होंने विज्ञान जगत के सामने रखा अपना स्वनियोजित और स्वनिर्मित पहला कृत्रिम बैक्टीरिया. कहते हैं, कृत्रिम जीवधारियों की रचना के द्वारा वे दुनिया के सामने खड़ी ऊर्जा समस्या को हल करने और जलवायु परिवर्तन को रोकने में सहायक बन सकते हैं. वेंटर के मुताबिक, "डिज़ाइन किए हुए, कृत्रिम आणविक जीवों के द्वारा हम बड़ी-बड़ी सामाजिक समस्याओं को हल कर सकते हैं. वैकल्पिक ऊर्जा पैदा कर सकते हैं."
क्रेग वेंटर शायद ही कभी हंसते हुए दिखाई पड़ते हैं. उन की प्रयोगशाला खूब कमाई कर रही है. अन्य वैज्ञानिक या तो उन्हें कोसते-धिक्कारते हैं, या मन ही मन पूजते हैं. उनकी खिल्ली अब कोई नहीं उड़ाता..
By.-Susheel Dwivedi
www.bioguruindia.blogspot.com
बड़बोला भगवानः क्रेग वेंटर
दस साल पहले अमेरिकी वैज्ञानिक क्रेग वेन्टर ने बड़े गर्व से घोषणा की थी कि उनकी प्रयोगशाला सेलेरा जीनोमिक्स में मानवीय जीनोम के अधिकांश जीनों को पढ़ लिया गया है. लेकिन जीवन की जटिलता को सामने आने में अभी और वक्त लगेगा.
क्रेग वेन्टर को गर्व इस बात का भी था कि सरकारी सहायताओं से चल रहा अंतरराष्ट्रीय ह्यूमन जीनोम प्रॉजेक्ट इस काम में पिछड़ गया था. उनकी घोषणा से दोनों के बीच प्रतियोगिता और भी तेज़ हो गई. लेकिन जून 2000 में दोनों ने मिल कर मानवीय जीनोम का एक आरंभिक नक्शा पेश किया. उस समय वेंटर ने कहा, "मैंने दूसरे लोगों की टीका टिप्णियों की कभी परवाह नहीं की. मैं मेहनत से काम करता हूं. अधिक से अधिक जानकारियां जुटाता हूं और अपनी राय आप बनाता हूं.
इस बीच अनुवंशिक जीवविज्ञान में बहुत प्रगति हुई है. मानवीय जीनभंडार यानी जीनोम को विकोडित कर लेने से सारी बीमारियों पर विजय पा लेने का सब्ज़बाग हालांकि अब भी टेढ़ी खीर है, तब भी यह तो मानना ही पड़ेगा कि मनमौज़ी क्रेग वेंटर के भड़काऊ कामों ने इस क्षेत्र में एक क्रांति-सी ला दी है. वह कहते हैं, "ऐसे भी लोग होते हैं, जो हाई स्कूल से आते ही अपना विचार बना चुके होते हैं. वे जानते हैं कि उन्हें क्या करना है और वे अपना विचार कभी बदलते नहीं. मैं अब भी जानने में लगा हूं कि मैं अभी और क्या कुछ कर सकता हूं."
बड़बोली बातें
वेंटर का बड़बोलापन कड़वा भले ही लगे, लेकिन वह अपना काम कर जाता है. 1998 में उन्होंने मानवीय जीनों की कोड भाषा को पढ़ कर उनका नक्शा बनाने के लिए सेलेरा जीनोमिक्स की स्थापना की. हालांकि इसी काम के लिए ह्यूमन जीनोम प्रॉजेक्ट नाम से एक अंतरराष्ट्रीय परियोजना 1990 से ही चल रही थी. वेंटर ने अपनी निजी प्रयोगशाला में यह काम सरकारी पैसों से चल रही अंतरराष्ट्रीय परियोजना से पहले ही लगभग पूरा कर लिया.
अंतरराष्ट्रीय परियोजना में काम कर रहे वैज्ञानिकों की सुस्ती पर कटाक्ष करते हुए वेंटर कहते हैं, "मैं भी यदि उनकी तरह समझौतावादी और सुस्त रहा होता, तो मानवीय जीनोम आज तक पढ़ा नहीं जा सका होता."
भगवान बनने का दंभ
63 वर्ष के वेंटर कहीं न कहीं भगवान बनने और दुनिया को कुछ देकर जाने के उत्कट अभिलाषी लगते हैं. तभी तो वह कहते हैं, "हो सकता है कि मेरी बात साइंस फ़िक्शन जैसी लगे, लेकिन योजना और आनुवंशिक चयन एक दिन डार्विन के विकासवाद का स्थान ले लेंगे."
वेंटर अपने विज्ञान के लिए नैतिकता की कोई सीमारेखा स्वीकार नहीं करते. उनकी अगली ज़िद है मनुष्य का बनाया कृत्रिम जीवन पैदा करना. 2007 में उन्होंने विज्ञान जगत के सामने रखा अपना स्वनियोजित और स्वनिर्मित पहला कृत्रिम बैक्टीरिया. कहते हैं, कृत्रिम जीवधारियों की रचना के द्वारा वे दुनिया के सामने खड़ी ऊर्जा समस्या को हल करने और जलवायु परिवर्तन को रोकने में सहायक बन सकते हैं. वेंटर के मुताबिक, "डिज़ाइन किए हुए, कृत्रिम आणविक जीवों के द्वारा हम बड़ी-बड़ी सामाजिक समस्याओं को हल कर सकते हैं. वैकल्पिक ऊर्जा पैदा कर सकते हैं."
क्रेग वेंटर शायद ही कभी हंसते हुए दिखाई पड़ते हैं. उन की प्रयोगशाला खूब कमाई कर रही है. अन्य वैज्ञानिक या तो उन्हें कोसते-धिक्कारते हैं, या मन ही मन पूजते हैं. उनकी खिल्ली अब कोई नहीं उड़ाता..
By.-Susheel Dwivedi
www.bioguruindia.blogspot.com
Wednesday, April 7, 2010
Science study material
Chapter -1
Chemical Reactions and Equations
Q.1. What is the general name of substances which are added to fat & oil containing
food to prevent rancidity. (1 Mark)
Ans. Antioxidants
Q.2. Write balanced chemical equation for the reaction of barium chloride with
Aluminium sulphate. (1 Mark)
Ans. 3 BaCl2 + Al2 (SO4)3 3 BaSO4 +2AlCl3.
Q.3. Identify the substance that is oxidised and the substance that is reduced in the
following reaction. 4 Na+O2 2 Na2O (1 Mark)
Ans. Substance Oxidised Na
Substance reduced O2
Q.4. Why does the colour of copper sulphate solution fade when iron nail is dipped in
it. (2 Mark)
Ans. The solution changes into iron sulphate Fe+CuSO4 FeSO4 + Cu
Q.5. What happens when quick lime is added to water? Write the chemical equation.
Which type of reaction is it endothermic or exothermic? (2 Mark)
Ans. Calcium oxide reacts vigorously with water to produce slaked lime (Calciumm hydroxide)
CaO+H2O Ca (OH)2 +Heat energy. It is an exothermic reaction.
Q.6. Silver chloride turns grey when kept in sunlight. Write chemical equation for it.
What type of reaction is it? (2 Mark)
Ans. 2 Ag Cl Sunlight 2 Ag (S) + Cl2 (g). It is a decomposition reaction
where light energy is absorbed. So it is an endothermic reaction.
Q.7. What happens when potassium iodide solution is added to lead nitrate solution? Give equation of the reaction involved. What type of reaction is represented by this example? (3marks)
Ans. When potassium iodide solution is added to lead nitrate solution, then a yellow
precipitate of lead iodide is formed alongwith potassium nitrate solution
Pb(NO3)2 (aq) + 2KI (aq) PbI2 (S) + 2 KNO3 (aq)
This is an example of a double displacement reaction. It is also a precipitation
Reaction.
Q.8. When a green iron salt is heated strongly, its colour finally changes to black and the odour of burning sulphur is given out.
a)Name the iron salt.
b)Name the type of reaction that take place during the heating of iron salt.
c)Write a chemical equation for the reaction involved. (3 Marks)
Ans:- a) Ferrous Sulphate
b) Thermal decomposition
c) 2 FeSO4 (S) Heat Fe2O3(s) + SO2 (g) + SO3 (g)
(Ferrous sulphate) (ferric oxide)
Green Colored Reddish brown.
Q. 9. Which type are the following reactions?
a) NH4Cl NH3 + HCl.
b) Fe + CuSO4 Fe SO4 + Cu
c) Ag NO3 + NaCl AgCl + NaNO3
d) PbO2 + SO2 PbSO4
e) CaCO3 CaO +CO2 (5 Marks)
Ans. a) Thermal decomposition reaction
b) Displacement reaction
c) Double displacement reaction
d) Combination reaction.
e) Thermal decomposition reaction
Q.10. Write balanced chemical equations for the following reactions:-
(5 Marks)
a) Dilute Sulphuric acid is poured on zinc granules
b) Iron reacts with steam
c) Carbon dixide reacts with water in the process of photosynthesis
d) Limestone is heated strongly.
e) Silver chloride is kept in sunlight in a china dish.
a) Zn + H2SO4 ZnSO4 + H2.
b) 3 Fe + 4H2O Fe3O4 + 4 H2
c) 6CO2 + 6H2O Sunlight C6H12O6 +6O2
d) CaCo3 Heat Chlorophyll CaO +Co2
e) 2 Ag Cl 2 Ag + Cl2
Chapter 2
Acids, Bases & Salts
1. How is the concentration of hydronium ion (H3O+) affected when a solution of an
acid is diluted? (1 Mark)
Ans. The concentration of hydronium ions, decreases when a solution of an acid is
Diluted.
2. Fresh milk has a PH of 6. How do you think the PH will change as it turns into curd? (1 Mark)
Ans. Its PH will decrease due to the production of lactic acid which is acidic in nature.
3. What is the PH of acid rains? ( 1 Mark )
Ans. Less than 5.6
4. Tooth enamel is one of the hardest substances in our body. How does it undergo
damage due to eating chocolates & sweets. What should we do to prevent it ?. ( 2 marks )
Ans. The bacteria present in mouth produce acids by the degradation of sugar & food
particles present in the mouth after eating. The acid so produced corrodes tooth
Enamel (Ca3(PO4)2). In order to prevent tooth decay we should clean the mouth
after eating food & we should use alkaline tooth paste.
5. Explain why for diluting an acid concentrated acid is added to water & not water to concentrated acid ?
Ans. This is because the process of dissolution of an acid in water is highly exothermic
process. For dilution the acid must be added slowly to water with constant stirring.
If water is added to acid, the heat generated may cause the mixture to splash out and cause burns. The glass container may also break due to excessive local heating.
6. A house wife found that the cake prepared by her is hard and small in size. Which
ingredients has she forgotten to add that would have made the cake fluffy? Give
reason.
Ans. She has forgotten to add baking powder. When baking powder is added [Sodium bicarbonate and tartaric acid mixture] during the preparation of cake and heated then
sodium bicarbonate reacts with tartaric acid to form CO2 gas. This CO2 evolved
makes the cake to rise and become light and fluffy. Since the cake prepared by the
house wife is small and hard, it means that she had forgotten to add baking
powder.
Q.7. You have been provided with three test tubes. One of them contains distilled water
and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, have will you identify the contents of each test
tube?
Ans. Dip red litmus paper in solution repeatedly in each tube.
(a)The tube in which the red litmus paper turns purple contains distilled water.
(b)The tube in which red litmus paper turns blue contains basic solution.
(c)The tube in which red litmus paper remains red contains acidic solution.
Q.8. Do basic solutions also have H+ (aq) ions? If yes, then why are these basic? What is an alkali ? (3 Marks)
Ans: Basic solutions also contain H+ (aq) ions. But in basic solutions:
[H+] <> 10-7 M
Since (OH-aq) is more than [H+aq]hence these are basic solutions.
Bases that are soluble in water are called alkalis. For example NaOH, KOH, Ca(OH)2
Q. 9. What is neutralization reaction? Write 3 applications of neutralization reaction.
Ans. Neutralization it is an interaction of an acid with a base to form salt and water.
e.g. HCI + NaOH NaCl + H2 O
Acid Base Salt Water
Q. 10. Application :(i) Antacids neutralize the excess acids in our stomach and relieve us
from pain Ex-magnesium hydroxide (milk of magnesia).
(ii) If the pH of the sail is less than 7 i.e. it is acidic, the farmer will treat the soil
with quick time, slaked time, chalk etc to neutralize the acidity.
(iii) Bee sting contains methanoic acid which causes pain and irritation. Use of
mild base. Ex baking soda neutralizes it.
Q 10. a) How do metal carbonates and metal hydrogen carbonates react with acids?
Explain with the help of an activity.
(b) What happens when sulphuric acid in rain reacts with calcium carbonate in buildings
Made from limestone? (5marks)
Ans. (a) All metal carbonates and hydrogen carbonates react with acids to form a
corresponding salt, carbon dioxide & water.
Metal Carbonate + Acid -> Salt + Carbon dioxide + water
Metal hydrogencarbonate + Acid -> Salt + Carbon dioxide + Water.
For ex, Sodium carbonate reacts with dilute hydrochloric acid as follows:-
Na2CO3 (S) + 2 HCI (aq) -> 2 NaCI (aq + H20 (l) + CO2 (g)
Sodium hydrogen carbonate reacts with dilute hydrochloric acid as follows:-
NaHCO3 (S) + HCI (aq) -> NaCI (aq) + H2O(l) + C02 (g)
Activity :- Text book page number 20 Activity 2.5
Observation:- CO2 is produced with an effervescence. When this gas is allowed to
pass through lime water it becomes cloudy. It is a test for CO2.
b) When sulphuric acid in rain reacts with calcium carbonate in buildings made
from limestone calcium sulphate and Carbon dioxide is produced.
CaCO3 + H2SO4 -> CaSO4 + CO2 + H2O.
Chapter -3
Metals & Non-Metals
Q.1. What would happen to a copper vessel if it is left for a few days in humid
atmosphere without being cleaned ? (1)
Ans:- The surface will get corroded with the formation of a green layer of copper
carbonate.
Q.2. Why is ZnO Called an amphoteric oxide? Show with the help an equation.
Ans. ZnO is called an amphoteric oxide because it shows both acidic as well as basic
behaviour, i.e., it reacts with both acids (eg. HCl) as well as bases(Eg. NaOH) to form salt & water.
ZnO + 2HCl -> ZnCl2 + H2O
ZnO + 2 NaOH -> Na2 ZnO2 + H2O
Q.3. Write the chemical equation for the reaction of hot aluminium with steam.
Ans. 2 Al + 3 H2O -> Al2O3+ 3H2
Q4. An element reacts with oxygen to form an oxide which dissolves in dilute HCl. The
Oxide also turns a solution of red litmus blue. Is the element a metal or a non-metal?
Explain with help of a suitable example.
Ans. The element is a metal. Taking the example of Na Metal, its oxide will be Na2O . It
dissolves dilute HCI as follows:
Na2O + 2 HCI -> 2NaCl + H2O
Na2O as well as all other metal oxides are basic. For example, Na2O is basic as it dissolves in water to form NaOH which is a base. Basic oxides turn red litmus blue.
Q.5. Give reasons for the following:
(i) Carbon is not used for making aluminium from aluminium oxide.
(ii) Al easily combine with oxygen but still can be used for making kitchen utensils. (2)
Ans. (i) Carbon is not used for making aluminium from aluminium oxide because
aluminium has greater affinity to oxygen than for carbon. Hence carbon cannot
reduce aluminium oxide to aluminium.
(ii)Aluminium easily combines with 02 to form a layer of aluminium oxide. This layer, however, acts as a protective layer and doesn’t allow the metal underneath to react further.
Q.6. What is activity series of metals? Arrange Al, Zn, and Mg. in an increasing order of reactivity. (2)
Ans. The arrangement of metals in order of their decreasing reactivity with respect to other is called activity series of metals. The increasing order of the given metals is: Hg <> Zn SO4 + Cu
(iii) Reaction of metals with HNO3 doesn’t evolve H2 gas. It is because HNO3 is a strong oxidizing agent. It oxidizes H2 produced to water and is itself reduced to any of its oxides such as N20. NO. or NO2.
Q8. Write chemical equations for the reactions taking place when
i)Zinc carbonate is calcined
ii)Cinnabar (HgS) is heated in the air.
iii)Manganese dioxide is heated with aluminium powder. ( 3 )
Ans. i) Zn CO3 (S) Calcination ZnO (S) + CO2 (g)
ii) 2HgS (S) + 302 (g) Heat 2HgO (S) + 2SO2 (g)
2HgO-> 2Hg (l) + O2 (g)
iv)3MnO2 + 4 Al. Heat 2Al2O3 + 3 Mn.
Q. 9. a) What is ionic bond?
b) How ionic bond is formed?
c) Write the formation of magnesium chloride. (5)
Ans. (a) The Chemical bond found by the transfer of electrons from one atom to another
is known as an ionic bond.
(b)An ionic bond is formed when one of the atoms can donate electrons to achieve the inert gas electronic configuration and other atoms need electrons to achieve the inert gas electronic configuration. When a metal (Usually 1, 2 or 3 electrons in outermost shell) reacts with a non-metal (usually 5, 6 or 7 electron in outermost shell), transfer of electrons takes place from metal atoms to the non-metal atoms and an ionic bond is formed.
(c)Formation of magnesium chloride (MgCl2). The atomic number of magnesium is 12. it has two electrons in its valence shell as shown below:
12 Mg – 2, 8, 2
Magnesium, therefore, has a tendency to lose the 2 valence electrons and in the
process attains the electronic configuration of neon
Mg-> Mg 2+ + 2e-
2, 8, 2 2,8
Chlorine (atomic number 17 ) has 7 electrons in the valence shell. It has a tendency to gain one electron to complete its octet.
Cl + e- Cl-
2,8,7 2,8,8
Thus, when magnesium and chlorine are brought together, the magnesium atom transfers its two valence electrons to two chlorine atoms. In the process both the atoms acquire the stable electronic configuration of nearest inert gases. The positively charged magnesium ion Mg2+ and negatively charged Chloride ions (Cl-) are now held together by the electrostatic force of attraction.
‾
Mg2+ + 2 Cl- Mg2+ 2 Cl- or MgCl2
This process can also be shown as below
(Mg 2+) [ ] 2 Mg xx
Q. 10. What is the difference between alloy & amalgam? Write the composition of brass & bronze. Write 2 properties of alloy. (5)
Ans. (a) Alloy – It is a homogeneous mixture of 2 or more metals or a metal and a non-metal.
Amalgam – If in an alloy one of the metals is mercury, then the alloy is an amalgam.
(b) Brass – Alloy of Copper and Zinc.
Bronze – Alloy of Copper and tin.
(c) Properties of alloy – (i) The electrical conductivity and melting point of an alloy is
less than that of pure metal.
(ii) Alloy does not corrode easily.
CHAPTER-4
Carbon and its Compounds
Q1. What is denatured alcohol? (1)
Ans:- Ethane is made unfit for drinking by adding poisonous substances like methane to it. Dyes are also added to colour the alcohol blue so that it can be identified easily. This is called denatured alcohol.
Q2. Name the product other than water formed on burning of ethanol in air? (1)
Ans:- Carbon dioxide gas.
Q3. Give the names of the functional groups: (1)
a) CHO b) C
Ans:- a) Aldehyde b) Ketone.
Q4. Why carbon forms compounds by sharing of electrons and not by formation of ions? ( 2)
Ans:- Carbon is tetravalent in nature. If it gains 4 electrons to form C 4- ions, then it will be difficult for 6 protons to hold on to 10 electrons.
To lose 4 electrons forming C4 + ion, it would require a large amount of energy to remove 4 electrons. Hence it forms bond by sharing of electrons.
Q5.Allotropy is a property shown by which class of substances: elements, compounds or mixtures? Give one example of allotropy. ( 2)
Ans. Elements show allotropy. For example, graphite, diamond and fullerenes are allotropic forms of carbon.
Q6. Under what conditions can a saturated hydrocarbon produce a sooty flame? (2)
Ans. Saturated hydrocarbon produce sooty flame only when burnt in limited supply of oxygen.Due to limited supply of oxygen, the incomplete combustion of the hydrocarbon takes place resulting in unburnt carbon producing sooty flame.
Q7.a) Draw the structure for the following compounds: (3)
i)Propanoic acid.
ii)Butanal
b) Why is conversion of ethanol acid considered as oxidation reaction?
ANS. a) H H O
H C C C OH
H H
Propanoic acid
H H H H
H C C C C = 0
H H H
Butanal
b) Ethanol is oxidised with alkaline potassium permanganate to form ethanoic acid. As the addition of oxygen takes place,therefore it is called oxidation reaction.
Q8. What happens when an ester is heated with a base such as sodium hydroxide? Write equation of the reaction which takes place? What is the special name for this reaction and for what purpose it is used? (3)
Ans. When an ester is heated with sodium hydroxide solution then the ester gets hydrolysed to form the parent alcohol and sodium salt of the carboxylic acid .
Example---When ethyl ethanoate ester is boiled with sodium hydroxide solution, then sodium eyhanoate and ethanol are produced.
CH3COOC2H5 + NaOH ---------CH3COONa + C2H5OH
Sodium Ethanol
Ethanoate
The alkaline hydrolysis of esters is known as saponification (soap making).This is because of the fact that this reaction is used for the preparation of soaps. When the esters of higher fatty acids with glycerol (oils and fats) are hydrolysed with sodium hydroxide solution,we get sodium salt of higher fatty acids which are called soaps.
.
Q9 a)What is the difference between soap and detergent in chemical composition ?
b)Why detergent remains effective in hard water while soap not for cleaning?
c)Explain the mechanism of the cleaning action of soap. (5)
Answer:- a) Soap:- It is sodium or potassium salts of long chain carboxylic acid.
Detergent:- It is ammonium or sulphonate salts of long chain carboxylic acids.
b) Soap reacts with calcium and magnesium chloride or sulphate which causes hardness of water to form an insoluble substance (scum). The charged ends of detergents donot form insoluble precipitates with the calcium and magnesium ions in hard water. Thus, they remain effective in hardwater.
c) Most dirt is oily in nature. Oil does not dissolve in water. The molecule of soap has two ends with differing properties. The ionic-end of soap dissolves in water while the carbon chain dissolves in oil. The soap molecules, thus form structures called micelles where one end of the molecule is towards the oil droplet while the ionic end faces outside. This forms an emulsion in water. The soap micelles thus helps in dissolving the dirt in water and we can wash our clothes clean.
10) Write the chemical equation for the following reaction:
a) Ethanoic acid with Sodium Carbonate
b) Ethanoic acid with Sodium Bicarbonate
c)Burning of Ethanol
d)Ethanoic acid with Sodiun Hydroxide
e) Heating Ethanol at 443K with excess concentrated sulphuric acid (5)
Anwser:- a)2CH3COOH + Na2Co3 2CH3COONa + H2O + CO2
b) CH3COOH + NaHCO3 CH3COONa + H2O + CO2
c)CH3CH2OH + O2 CO2 + H2O + heat and light
d) NaOH + CH3COOH CH3 COONa + H2O
Hot conc.
e) CH3 CH2OH CH2 = CH2 + H2O
H2SO4
5. PERIODIC CLASSIFICATION OF ELEMENTS
Q.1.What were the criteria used by Mendeleyev in creating his periodic table?
Ans.In creating his periodic table, Mendeleev was guided by two factors:-
(a). Increasing atomic masses and;
(b) Grouping together of elements having similar properties.
Q.2.Besides Gallium, which other elements have since been discovered that fill the gaps left by Mendeleev in this periodic table?
Ans.Scandium and Germanium.
Q.3.Name two elements you would expect to show same kind of chemical reactivity as Magnesium. What is your best choice?
Ans.Beryllium, Calcium and Strontium will show same kind of chemical reactivity as Magnesium because they are placed in the same group. Elements placed in the same group have similar outer electronic configuration.
Q.4.Looking at the resemblance of Hydrogen to alkali metals and the Halogen family, to which group and period should Hydrogen be assigned in Mendeleev’s periodic table?
Ans.Since properties of Hydrogen resemble both alkali metals and Halogens, it can be placed either in group IA or group VII A. Since Hydrogen has the lowest atomic mass, it is placed in period I.
Q.5.An atom has electronic configuration 2, 8, 7.
(a) What is the atomic number of this element?
(b) To which of the following elements would it be chemically similar:-
(i) 7N
(ii) 9F
(iii)15P
(iv)18Ar
Ans. (a) The atomic number of the element is 2+ 8+7=17.
(b) Electronic configurations of the given elements are:-
(i)N-2,5.
(ii)F-2,7.
(iii)P-2,8,5.
(iv)Ar-2,8,8.
Thus F having similar electronic configuration with 7 valence electrons would be chemically similar to the given element.
Q.6.The positions of three elements A, B, C in the periodic table are show below:-
Group 16 Group 17
- -
- A
- -
B C
(a) State whether C is a metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller than B in size?
(c) Which type of ion (cation or anion) will be formed by element A?
Ans.(a) Elements of group 17 have 7 electrons in their respective valence shell and have a strong tendency to gain an electron to complete their octet. So, A is a non-metal.
(b) On moving down a group, the atomic size increases and thus the force of attraction of the nucleus for the incoming electrons decreases. Hence the reactivity decreases. Therefore C is less reactive than A.
(c) B and C belong to the same period. On going from left to right in a period the nuclear charge increases but the number of shells remain same. Therefore atomic size decreases from left to right. Thus C is smaller in size than B.
Q.7.Use Mendeleev’s periodic table to predict the formulae for the oxides of K, C, Al, Si and Ba.
Ans.K2O, CO2, Al2O3, SiO2, BaO.
Q.8.A metal M forms an oxide having the formula M2O3. It belongs to third period of the modern periodic table. Give its atomic number and valency.
Ans.Atomic number of the element is 2, 8, 3=13 and its valency is 3.
Q.9.What are the uses of Modern Periodic table?
Ans.In modern periodic table, the elements with similar properties are placed together in the same group. If we know the properties of one element of the group, the properties of other elements of the group can be predicted. Thus it makes the study of elements systematic.
Q.10.Why is long form periodic table regarded better than Mendeleev’s periodic table?
Ans.It is due to the following reasons:-
(a)It is based on atomic number.
(b)There is no confusion regarding the position of isotopes.
(c)All groups are independent and there are no sub-groups.
(d)It is more systematic.
Chapter 6
Life Processes
VSA Question carrying 1 marks each
Q1. What are the main two types of nutrition?
Ans. Autotrophic and Hetrotrophic nutrition.
Q2. what does the word ‘Sapro’ mean?
Ans. The word Sapro means rotten.
Q3. What is the process of obtaining food in Amoeba called?
Ans. The process of obtaining food in Amoeba is called Phagocytes.
Q4. name the cellular organelles where the folloing processes take place (i) Photo synthesis (ii) Cellular aerobic respiration?
Ans. (i) Chloroplast (ii) Mitochondria.
Q5. What is the function of bile?
Ans. Bile brings about the emulsification of fats.
Q6. Where are hormones synthesized in plants?
Ans. In planyts hormones are synthesized in the shoot and root tips.
Q7. Name the largest artery in our body?
Ans. Aorta
Q8. What is the liquid part of blood called?
Ans. Plasma.
SAQ carrying 2 marks each.
Q1. What is emulsification?
Ans. Breakdown of the large fat droplets into smaller ones.
Q2. Why are plants green?
Ans. Plants posses green chloplastic pigments called chlorophyll which absorb most of the blue and red regions of the incident light. They reflect green light so the plants look green in colours.
Q3. State the function of epiglottis?
Ans. Epiglottis is a leaf like cartilaginous flap present at the anterior end of glottis. It closes the glottis during swallowing to check the entry of food into glottis.
Q4. In which form is (i) Carbohydrates stored in plants (ii)Food stored in animals.
Ans. (i) Carbohydrates are stored in the form of starch in plants.
(ii) In animals food is stored in the form of glycogen.
Q5. What is breathing?
Ans. It is aphysical process of inhalation or bringing in fresh air for obtaining oxygen and exhalation or taking out of foul air for elimination of CO2.
SAQ carrying 3 marks each.
Q1. Why are white blood corpulses called “Soldiers” of the body?
Ans. White blood corpulses are called soldiers of the body because they protect the body from infections by destroying foreign matter. They also manufacture antibodies which are responsible for immunity.
Q2. What happens to glucose which enters nephron along with filtrate during excretion in human beings. State two vital functions of kidney.
Ans. Glucose is reabsorbed in tubule.
Vital functions of kidney (i) Excreation, separation of nitrogenous wastes for elimination.
(ii) Osmoregulation, maintainance of balance of water and salts in the body through elimination if extra and retention if deficient.
Q3. When is blood clotting useful?
Ans. Cloting of blood is useful phenomenon to stop flowing of blood (bleeding) during cuts and accidents and at the time of accidents.
Q4. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Ans. Mammals and birds are warm blooded animals. They continiously use energy to maintain treir body temperature. They have a higher energy need and require more oxygenated blood for their cells. It is important that their oxygenated blood doesnot mixup with deoxygenated blood.
Long Answer Question carrying 5 marks.
Q1. Name the blood vessel that brings deoxygenated blood to the human heart (b) Which chamber of human heart receives oxygenated blood (c) Explain how oxygenated blood from this chamber is sent to all parts of the body?
Ans. (a) Pulmonary vein.
(b) Left arterium.
(c) After receiving the deoxygenated blood, the atium contract during this countraction the deoxygenated blood of the right atium is poured into the right ventricle. Then the ventricle contract and the deoxygenated blood flows to the lungs through pulmonary artery.
CHAPTER 7
CONTROL AND COORDINATION
Q1 Which gland secretes the growth hormone? (1)
Ans Pituitary gland (anterior lobe of pituitary).
Q2 Name the part of the hindbrain which is responsible for maintaining the posture and balance of the body. (1)
Ans Cerebellum.
Q3 Which hormone is responsible for the development of moustache and beard
in man ?
Ans Testosterone
Q4 Why is the use of iodised salt advisable ? (2)
Ans Iodine is essential for the synthesis of thyroxin hormone in the thyroid gland.
Thyroxin regulates carbohydrates , protein and fat metabolism in the body so
. as to provide the best balance for growth .In case of deficiency of iodine in
our diet , there is a possibility that we might suffer from goitre . Thus , use
of iodised salt is advisable to prevent iodine deficiency in the body .
Q5 Why are diabetic patients advised to take less sugar in their diet by the
doctor ? (2)
Ans Insulin hormone is secreted by the pancreas which helps in regulating blood
sugar level in our body .It is not secreted in proper amount in the body of
the diabetic patient. If the sugar level in the blood rises , it causes many
harmful effects . So the diabetic patients are advised to take less sugar .
Q6. What happens at the synapse between two neurons ? (2)
Ans. The information acquired at the end of the dendrite tip of a nerve cell sets
of a chemical reaction that creates an electrical impulse This impulse travels from the dendrite to the cell body , and then along the axon to its end .At
the end of the axon , the electrical impulse sets off the release of some
chemicals . These chemicals cross the gap or synapse and start a similar
electrical impulse in a dendrite of the next neuron .
Q7. What is the difference between sensory and motor neurons? Which part of the brain
is responsible for auditory reception and sensation of smell? (3)
Ans. Sensory neurons-These are the neurons that transmit impulses towards the central
nervous system (brain and spinal chord) through their axons.
Motor neurons- These are the neurons that transmit impulses from central nervous
system towards effectors (muscles or glands).
Specific part of brain is responsible for auditory reception and smell.
Q8 Draw a human brain and label its different parts? (3)
Ans Text book page no.118 & fig.7.3.
Q9 What is a reflex action? Explain with help of an example. Draw a labeled diagram
to show the reflex action? (5)
Ans a) Reflex action is spontaneous & involuntary response of effectors (muscles &
glands) to stimulus. It is extremely quick action that does not involve any thinking
by the brain.
b) When our hand accidentally touches the hot object, heat is sensed by the thermo receptors present in the skin of hand. The receptor triggers nerve impulse in sensory neuron. It transmits message to spinal cord. In spinal cord impulse is passed on to the relay neuron which ,in turn passes it to the motor neuron. The motor neuron transmits the instruction to a muscle in our arm. The arm muscles contract and pulls our hand away from the hot object.
c) Text book page no.117 fig7.2
Q10. a)How is the movement of leaves of a sensitive plant different from the movement of the shoot towards light? 5)
b)Name one plant hormone that promotes growth in plant and one plant hormone that inhibits growth?
c)How does phototropism occur in stem?
Ans a) The movement of leaves of a sensitive plant is neither towards nor away from stimulus like touch. While movement of shoot is towards stimulus like light .The movement of leaves of a sensitive plant is not directional while the movement of shoot is directional.
b)Plant hormone that promotes growth in plants-Auxin
Plant hormone that inhibits growth-Abscisic acid.
c)The movement of a plant part in response to light is called phototropism.
The shoot responds by bending towards light while roots respond by bending away from the light. We know that the plant stem responds to light and bends towards it due the action of auxin hormone.This happens as follows:
i)When sunlight comes from above, then the auxin hormone present in the tip of the stem spreads uniformly down the stem .Due to the equal presence of auxin, both the sides of the stem grow straight and with some rapidity.
ii)When the light falls on the right side of the plant, then the auxin hormone collects in the left side of the stem, away from the light. This is because auxin hormone prefers to stay in shade.
Thus more auxin hormone is present in the left side of the stem as compared to the right. The left side of stem, hence grows faster than its right side and therefore, the stem bends towards the right side (direction of light).
8.
Q1 Name any two sexually transmitted diseases?
Ans: 1] Gonorrhoea 2] syphilis
Q2 Write full form of IUCD and AIDS?
Ans: IUCD-Intra Uterine Contraceptive Device.
AIDS-Acquired Immuno Deficiency syndrome.
Q3 Where does fertilization take place in human female?
Ans: Fertilization takes place inside the fallopian tubes.
Q4 If a women is using Copper-T, will it help her in protecting sexually transmitted diseases?
Ans: Copper-T prevents fertilization but the chances of infection persist. So, Copper-T will not help her in protection against sexually transmitted diseases.
Q5 What are the advantages of sexual reproduction over asexual reproduction?
Ans: Due to reshuffling of chromosomes and crossing over, sexual reproduction brings about variation in almost all characters so that no two individuals are similar. Genetic changes contribute to evolution of species to form better organisms. Asexual reproduction does not contribute to evolution of species as there is no variation.
Q6 Why is vegetative propagation practiced for growing some type of plants?
Ans: Vegetative propagation is practiced in some plants because-
1.It is the only method of reproduction in seedless plants.
2.A full matured plant is obtained in a very short time.
3.It helps to preserve the characters of the plant the breeder desires.
4.It is an easy and economical method for multiplication of ornamental plants.
Q7 How does reproduction helps in providing stability to population of species?
Ans: Reproduction helps in providing stability to population by-
1.Introducing variation in the population through genetic combination that helps the population to tide over adverse environmental conditions and adapt to changing environment.
2.Balancing birth and death rate.
Q8 What could be the reasons for adopting contraceptive methods?
Ans: Contraceptive methods are adopted for the following purposes-
1.To avoid frequent and unwanted pregnancies.
2.To maintain good reproduction health.
3.To obtain protection from sexually transmitted diseases.
4.To restrict the number of children.
Q9 Differentiate between menarche and menopause?
Ans- Commencement of menstruation at puberty in human female is termed menarche and its stoppage at the age of 50yrs is called menopause.
Q10 What is the importance of DNA copying in reproduction?
Ans-DNA copying is an important phenomenon of reproduction through which the organisms pass their features to their offsprings. It maintains the genetic pool and the body design features in different generation of the species. DNA copying also produces variations due to genetic linkage and crossing over of chromosomes. Such variations are useful for the survival of species.
9.
Q1:-Give examples of two variations found in humans.
Ans: - 1. Human height
2. Free earlobe and attached earlobe
Q2:- Write the names of the components of DNA?
Ans: - Components of DNA are nucleotides. Each nucleotide has further three components-
1.Deoxyribose sugar
2.A nitrogenous base
3.A phosphate group
Q3:-Give two examples where environmental factors govern sex-determination?
Ans: - a) In turtle, high incubation temperature results in the development of female progeny.
b) In lizard high incubation temperature results in male progeny.
Q4:- What is genetic engineering? Give the full form of GMO.
Ans: - It is the technique of altering the genetic make up of an organism by inserting gene (or segment of DNA) from other organism into its DNA.
The full form of GMO is GENETICALLY MODIFIED ORGANISM.
Q5:- How are the areas of study – evolution and classification interlinked?
Ans:-Classification of organisms is based on relative similarities and differences among organisms. Resemblances in organisms are because they have arisen from a common ancestor and differences are due to adaptations to different types of environment. As the organisms can be graded in order of increasing complexity, it indicates the concept evolution.
Q6:-Why are small numbers of surviving tigers a cause worry from the point of view from genetics?
Ans: - With decreasing number of tigers, their genetic pool is also vanishing which is essential to maintain the ecological and food chain balance.
Q7: - Will geological isolation be a major factor in the speciation of an organism that reproduces asexually? Why or Why not?
Ans: -During asexual reproduction organisms undergo a little variation over generations .The variation in the genetic pool are not enough to raise a new species .Thus, any change resulting from geographical isolation may not be passed to the next generation.
Q7: -A man with blood group ‘A’ marries a women blood group ‘O’ and their daughter has blood group ‘O’. Is this information enough to tell you which of the traits –blood group ‘A’ or ‘O’ is dominant? Why or Why not?
Ans: - Blood group ‘A’ is dominant while ‘O’ is recessive character. If a man with blood group ‘A’ marries a woman with blood group ‘O’ and their daughter has blood group ‘O’ , then the man has one copy of ‘A’ and one copy of ‘O’ blood group.
Q8: - Differentiate between autosomes and sex chromosomes.
Ans: - 1. The pair of chromosomes that are responsible for development of body characters are called autosomes .In human body, there 22 pairs of autosomes.
2.The pair of chromosomes which are responsible for determining the sex of the individual called sex chromosomes .
Q9: -Why Mendel selected garden pea plant for his experiment.
Ans: - Mendel selected garden pea plant for his experiment because-
1. Pure varieties of pea were available.
2. Pea plants showed a number of easily detectable contrasting characters.
3. The flower structure of pea is such that it allows controlled breeding.
4. Pea flower normally remains closed and undergoes self pollination.
Q10:-How is the equal genetic contribution of male and female parents ensured in the progeny?
Ans:-The gametes responsible for the formation of progeny develop by the process of meiosis. During meiosis only one set of chromosomes (50% of Gene) is transferred to the gamete. When male and female gametes fuse, one set of chromosome from each parent cell come together and complete the genetic pool.So, progeny receives 50% genetic contribution through each gamete(male and female).
10.LIGHT – REFLECTION AND REFRATION
Q1:- Define 1 dioptre of power of lens?
Ans: - One dioptre is the power of a lens of focal length one metre.
Q2:- Why do you prefer convex mirror as a rear-view mirror in vehicles?
Ans: - A convex mirror produces an erect and highly diminished image of the objects.Further, since it is curved outwards; it gives a wider field of view.
Q3:- The refractive index of diamond is 2.42.What is the meaning of the statement?
Ans: - It means that light travels 2.42 times faster in vacuum than in diamond.
Q4:- One half of a convex lens is covered with a black paper. Will this lens produce a complete image of that object? Verify your answer experimentally. Explain your observation.
Ans:- Yes ,it will produce a complete image of the object.
This can be verified experimentally by observing the image of the distant object like tree on a screen when lower half of the lens is covered with a black paper. However, the brightness of the image gets reduced.
Q5:- How can you distinguish between a convex mirror, a plane mirror and concave mirror?
Ans: - With the help of virtual image of three mirrors, we can distinguish between three mirrors-
a)Plane mirrors will produce virtual image of the same size.
b)Concave mirrors will produce magnified virtual image.
c)Convex mirror will produce a diminished virtual image.
Q6:- The magnification produced by a plane mirror is +1.What does this mean?
Ans:- m = h’/h=1
Therefore, h’ = h
i.e, the size of the image is equal to the size of the object. +ve sign of m indicates that the image is virtual.
Q7:- Calculate the distance at which an object should be place in front of a thin convex lens of focal length 10cm to obtain a virtual image of double its size?
Ans:- f = +10cm
m = +2 (as the image is virtual)
As, m = v/u = 2
Or, V = 2u
As, 1/v -1/u = 1/f
Or, 1/2u - 1/u = 1/10
Or, - 1/2u = 1/10
Therefore u = -5cm
The object should be place at a distance of -5cm from the lens.
Q8:- A concave mirror of focal length 20cm is to be used as a shaving mirror. Which of the following is the suitable object distance from the mirror? Justify your answer.
a)10cm
b)20cm
c)30cm
Ans:- For using concave mirror as shaving mirror, uQ9:-Light enters from air into diamond. Which has a refractive index of 2.42? Calculate the speed of light in diamond. (The speed of light in air is 3 x 108 m/s)
Ans:-
As, n = c/v
V = c/n
= 3 x (10)8/2.42
= 1.24 x 108 m/s
Q10:- A concave mirror of focal length 15cm forms an image of an object kept at a distance of 10cm from the mirror. Find the position, nature and size of the image formed by it.
Ans:- Here ,
f = -15cm
u=-10cm
v=?
1/v= 1/f -1/u (mirror formula)
1/v= 1/ (-15) -1/ (-10)
= 1/10 – 1/15
= 3/30 -2/30
=1/30
Therefore, v = 30cm
Thus, the image is formed at 30cm from the mirror.
As, v is positive, the image is virtual and erect
As, m = -v/u
= - 30/ (-10)
=3
Therefore, the size of the image is three times the size of the object.
11.HUMAN EYE AND COLOURFUL WORLD
Q1:- Name the optical phenomenon responsible for formation of RAINBOW?
Ans:- Refraction, internal reflection and dispersion of light.
Q2:- What is meant by scattering of light?
Ans:-Scattering is the bouncing off of electro-magnetic radiations by atoms and molecules of the medium through which they are propagating.
Q3:- Why different colours deviate through different angles on passing through a prism?
Ans:- This is because different colours have different wavelengths and glass has different refractive index for different wavelengths .
Q4:-Which phenomenon of vision is used in cinematography?
Ans:-Persistence of vision.
Q5:- The near point of the hypermetropic eye is 1metre.What is the power of the lens required to correct this defect. Assume that near point of the normal eye is 25cm.
Ans: - Since, the near point of the hypermetropic eye is1m (100cm), the lens used should be such that the rays of light starting from normal near point(25cm) appear to come from the near point of hypermetropic eye.
Thus,
u = -25cm
v =-100cm
1/f =1/v -1/u
f = uv/u-v
= (-25) x (-100)/ (-25) – (-100)
=100/3
=33.3cm
P = 100/f
= 100/33.3
= 3 D
Since the power is positive , lens must be convex.
Q6:-The far point of a myopic person is 80cm in front of the eye. What is the nature and power of the lens required to correct the problem?
Ans:- Distance of far point ,x =80cm
P =?
For viewing distant objects, focal length of the corrective lens
f = - x = -80cm
P = 100/f
= 100/-80
=-1.25 D
The Lens is concave.
Q7:- Danger Signals are red in colour, why?
Ans:-Due to its longer wavelength, red colour is least scattered by fog or smoke.Thus, the red is visible in the same colour from large distances.
Q.8.Why do we have two eyes for vision and not just one?
Ans. (a) It gives a wider field of view.
(b).The ability to detect faint objects is enhanced with two eyes instead of one.
(c). Our eyes are separated by a few centimeters; each eye sees a slightly different image. Our brain combines the two images into one and thus provides a three-dimensional perception of the objects.
Q.9.What is persistence of vision?
Ans.The ability of an eye to continue to see the image of an object for a very short duration even after the removal of the object is called persistence of the vision. In human eye, vision persists for 1/16th of a second after removal of the object.
Chapter 12
Electricity
V.S.A Question (1 mark each)
1.What is the resistance of an ideal voltmeter and an ammeter?
Ans. Infinite and zero.
2.What is the value of charge on an electron in coulomb?
Ans. -1.6 x 10-19
3.Why is resistance more in combination of resistors?
Ans. In series combination of resistors, the effective length of the conducting path increases and as such resistance increases (R ∞l)
4.Name two special characters of a heater coil?
Ans. A heater coil should have (i) high resistivity (ii) high melting point.
5.What is the resistance of a connecting wire?
Ans. It is negligible, almost zero.
S.A.Q (2 marks each)
1. What is the difference between a resistor and resistance?
Ans. A resistor is an object where as resistance is its property due to which it obstructs the flow of electrons through it.
2.Electric current is flowing through a wire from west to east direction. What is the direction of motion of the conductor electrons in the wire?
Ans. From east to west as direction of electric current is opposite to the direction of flow of conduction electrons.
3.Why are the conductors of electric heating devices such as toasters and electric irons) made of an alloy rather than a pure metal?
Ans. It is because alloy is less affected by the rise in temperature than a pure metal. In other words alloys do not oxidise (or burn) easily at high temperature.
4.What will be the equivalent resistance R of two resistors R1 and R2 (i) connected in series and (ii) connected in parallel?
Ans. When connected in series
R=R1+R2
When connected in parallel
1/R=1/R1+1/R2 or R=(R1R2) /(R1+R2)
5.What will happen to current if the voltage across the circuit reduces to half its original value while the resistance of the circuit remains constant?
Ans. Current=Voltage/Resistance
If voltage becomes half its original value, the resistance remains the same, then current in the circuit will be reduced to half its original value.
SAQ (3 marks each)
1.A wire of resistance 5 ohm is bent in the form of a closed circle. What is the effective resistance between the two points at the ends of any diameter of the circle?
Ans. The length of the wire between two points at the ends of a diameter of a circle is half of the whole wire. The resistance of a conductor is directly proportional to its length.
Thus, the two resistance 5/2 Ω will be in parallel.
Let R be the effective resistance.
1/R=2/5+2/5
1/R=4/5
R=5/4=1.25 Ω
2.Calculate the effective resistance in the diagram given.
Ans. In this case resistance DA and AB are in series. DC and CB are also in series. But AD and AB together are in parallel to DC and CB together.
Thus, Resistance (DA + AB)=1+1=2Ω
and Resistance (DC + AB)=1+1=2Ω
Let Rp be the effective resistance, then (by parallel formula)
1/Rp=1/2+1/2
=(1+1)/2=2/2
Rp=1Ω
Thus, the combination has a resistance of 1 ohm.
3.Why does resistance of a conductor increase with increase in temperature?
Ans. When a metallic is heated the atoms in the metal vibrate with greater amplitude and frequency due to increase in temperature the thermal velocities of free electrons also increase. Therefore the numbers of collisions between free electrons and atoms increase. This increases the resistance of the conductor.
4.Why is it not advisable to handle electrical circuit with wet hands?
Ans. The resistance of dry skin human body is about 50,000Ω. When the skin is wet, the resistance is lowered to about 10,000Ω. If a person with wet hand touches the electrical circuit the current will flow suddenly due to less resistance. Therefore, it is advisable not to touch the electrical circuit with wet hands.
Long Answer Question (5 marks)
1.A dry cell should be used intermittently and not continuously. Explain why?
Ans. Hydrogen gas in the formed during the working of the dry cell. This gas in the form of bubbles forms an insulated layer around the carbon rod (i.e anode). As a result of this, the resistance of the cell is increased and hence the flow of charges in the cell is opposed. Ultimately, the dry cell stops working if used continuously. However, these bubbles of hydrogen gas are removed slowly by Mno2, which acts depolarizers. The dry cell can work if the bubbles of hydrogen gas around carbon rod are completely removed by Mno2. For this purpose time is required. So the dry cell should be used intermittently to provide sufficient time for the removal of hydrogen gas bubbles by manganese dioxide.
13.Magnetic effect of electric current
V.S.A.Q (1 marks)
1. What constitute the field of a magnet?
Ans. The space around a magnet within which its magnetic effect can be experienced, constitutes the (magnetic) field of the magnet.
2. What is meant by the following? A fuse is rated at 8 A?
Ans. It means that it burn if current exceeds 8A.
3.What is short circuiting in an electric supply?
Ans. Short circuiting in an electric supply occurs when the live wire touches the neutral wire.
4.What happens when a current carrying conductor is kept in a magnetic field?
Ans. It experience a force.
5.Are magnetic field lines open or closed curves?
Ans. They are closed curves.
6. What is the frequency of AC in India?
Ans. It is 50 Hz.
SAQ (2 marks)
1.Write down any two properties of magnetic field lines.
Ans. 1 It is directed from north pole to south-pole outside the magnet and inside the magnet it is vice-versa.
2.Two magnetic field lines never intersect each other.
2. What is electro-magnetic induction?
Ans. In reality it is the conversion of mechanical energy into electrical energy.
3.What is the role of each of the three pins in a power plug?
Ans. The thick pin at the top of a power plug is for earthing ,the live pin is on the left and the neutral pin is on the right of the power plug.
4. what are the two main precautions to be the taken while using an electric supply?
Ans. (i)Electric supply should be immediately switched off from the main switch in case a person touches a live wire or if there is a fire in the house.
(ii) Electric supply should also be switched off during natural calamities like earthquake, floods etc.
5.What is the difference between two circuits used in household electricity?
Ans. One of 15 ampere rating is used for higher power appliances and second of 5 ampere rating is used for bulbs, fans, etc. which are of lower power rating.
6.Two wires A and B suspended. These wires are connected in parallel with a battery as shown in figure. Will the distance of separation between the wires (i) remains the same or (ii) increases or (iii) decreases? Explain.
Ans. When wires are connected to battery in parallel, then the current in both the wires will attract each other, therefore the distance between the wire decreases.
SAQ (3 marks)
1.A circuit has a fuser of 5 A. What is the maximum number of 100 watt (220v) bulbs this can be safely used in the circuit?
Ans. Suppose x number of such bulbs can be used.
Power of one bulb =100 watt
Power of x bulb (p)=100 x X watts
Potential difference(v)=220 volts.
I=5 ampere
P=VI
= 100 x X= 220x5
X =220x5/100=11 bulbs
2.On what factors does the force experienced by a current carrying conductor placed in a uniform magnetic field depend?
Ans. The place in a uniform magnetic field depends on :-
(i)The length of the conductors(l).
(ii)The magnitude of current flowing through the conductor (l), and
(iii)The magnitude of the magnetic field of the conductor (B)
3.A fixed wire AB carries current I. An electron is moving parallel to the wire in which direction does the electron tend to move?
Ans. By right hand thumb rule, the magnetic field in the vicinity of wire is downward, perpendicular to the plane of the paper. The conventional direction of electrical current his opposite to the direction of motion of electron. By Fleming left hand rule the force on electron is always away from wire in the plane of paper; therefore, the electron will be deflected downward (away from the wire) in the plane of paper.
4.A cylindrical bar magnet is kept along the axis of a circular coil. Will there be a current induced in the coil if the magnet is rotated about the axis?
Ans. The magnetic field of a cylindrical magnet his symmetrical about the axis. As the magnet is placed along the axis of circular coil, there will be no induced current because the magnetic flux linked with the coil does not change due to rotation of the magnet.
LAQ (5 marks)
1.Answer the following
i.What is the phenomenon of electron magnetic induction?
ii.Which is the device used for producing current?
iii.What is the essential difference between AC generator and a DC generator?
iv.At the time short circuit, what happens to the current in the circuit?
v.Give the role of split ring in AC generator?
Ans. i) the phenomenon of electromagnetic induction is producing induced current in a coil due to relative motion between a magnet and the coil.
ii) The device used for producing current is generator
iii) The essential difference between an AC generator and DC generator is that AC generator has slip rings while the DC generator has a commutator.
iv)At the time of short circuit, the current in the circuit increases heavily.
v)The role of split ring is to reverse the direction of current through a circuit.
14.Sources of Energy
VSAQ (1 marks)
1.Name the two forms of energy usually at our homes?
Ans. Heat and electricity
2.Exposure to which component of solar radiation could be a health hazard?
And. Ultra violet radiation.
3.Name two forms in which solar energy manifests itself in oceans?
Ans. Tidal energy and ocean thermal energy
4.What are the sources of energy in nuclear fission and fusion?
Ans. The disappearance of certain mass ( m) in both the processes, fission and fusion. It appears as energy.
5.Which radiations of sunlight are used in heating a solar cooker?
Ans. Infra red radiations.
6.Name any two renewable sources of energy?
Ans. Solar energy and Geo-Thermal energy.
SAQ(2 marks)
1.Give any two peaceful uses of nuclear energy.
Ans. Nuclear energy can be used:
(i)for generating electricity
(ii)in the treatment of cancer
2.How is electrical energy obtained from nuclear reactors?
Ans.The large amount of heat produced during nuclear fission is treated to convert into steam. The steam is then used to drive turbines which are connected to electrical generators which convert it into electrical energy.
3.What is the purpose of glass sheet in solar heating devices?
Ans. Glass sheet has a property that permit the infra-red radiations of short wave length from the sun to get into heating device but does not allow IR radiations of longer wave length to leave the solar heating device.
4.Why is the use of charcoal discouraged although it is a better fuel than coal?
Ans. Because charcoal is prepared from destructive distillation of wood. So, for this purpose more and more trees would have to be cut down which causes deforestation. It affects the ecological balance of earth.
5.Can any source of energy be pollution free? Why or why not?
Ans. No source of energy can be perfectly pollution free but biomass energy, hydroenergy, wind energy, geothermal energy and solar energy is almost pollution free. If fossil fuel is allowed to burn in presence of excess of oxygen the pollution produced can be much reduced.
SAQ (3 marks)
1.If you could use any source energy for heating your food, which one would you use and why?
Ans. Fuel to be used should be easily accessible, should be easy to store and transport and should be economical. If we are in city area, LPG should be used since it does not produce pollution, is easily available and is economical.
In rural area, gobar gas or biogas should be used. It is almost free, has high calorific value and is pollution free. It is also renewable source of energy.
2.What is Bio-energy?
Ans. Bio-energy is the energy generated by biomass. Energy may be in form of fire, fuel oil, biogas, animal dung alcohol, charcoal or even human excreta. Fuels are derived from bio-mass. It is an indirect source of solar energy and is renewable source of energy.
3.Hydrogen gas has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG. Why or why not?
Ans. The by-product of hydrogen when used as a fuel and burnt is water while that of CNG are water and carbon dioxide gas. Water is an absolutely harmless by-product, however carbon dioxide in the environment causes green house effect leading to global warming. Hence, hydrogen can be called a cleaner fuel than CNG.
4.“Only a small part of the solar energy that strikes the upper regions of atmosphere, reaches the surface of the earth”. Discuss?
Ans. When the solar energy falls in the top surface of the atmosphere then some solar energy is reflected back into the space by the atmosphere, and the atmosphere also absorbs a lot of solar energy, for example most of the ultra violet rays are absorbed by the ozone layer. So the solar energy which reaches on the earth’s atmosphere is mainly in the form of heat rays (infrared rays) and visible light, which is a small part of the solar energy.
5.What is geo-thermal energy? What are its limitations?
Ans. Geo-thermal energy is the heat of the earth and is the naturally occurring thermal energy found within rock formations and the fluids held within those formations. Geo-thermal energy is on of those few sources that do not come directly or indirectly from the solar energy.
Limitations
i)Goe-thermal hot spots are scattered and usually some distance away from the areas that need energy.
ii)The overall power production has lower efficiency (about 15%) as compared to that of fossil fuels (35% to 40%)
iii)Though as a whole geothermal energy is inexhaustible, a single bore has a limited life span of about 10 yrs.
iv)Noise pollution is caused by drilling operations at geo-thermal sites.
LAQ (5marks)
1.What are environment consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Ans. The demand of energy consumption is increasing day to day. Exploiting any source energy may disturb the environment in one-way or other. For example getting energy from fossil fuel may cause lot of pollution in air. Getting energy from nuclear fission may create problem of disposal of nuclear waste.
Steps for reducing energy consumption should be such that we get maximum energy from least fuel. For this:
i.Under the given situation technology utilized should be the best possible. For example. Using smokeless chulhas should be preferred to traditional chulhas.
ii.Energy should be extracted by most economic method under the given situation. Where as energy extraction by solar cells may be useless in big towns due to cost factor, it may be indispensable for artificial satellites.
iii.Wastage of energy should be strictly avoided. Energy saved is equal to energy produced.
iv.Sources of energy should be such that it causes least damage to environment.
15.Our environment
VSAQ (1 marks)
1.Would you eat animals or plants to get more calories of heat?
Ans. We should eat plants to get more calories of heat.
2.What will happen if we kill all the organisms in one tropic level?
Ans.If we kill all the organisms in one tropic level, unbalances are created in the food chain.
3.Write an aquatic food chain?
Ans. Phytoplankton ton zooplanktonfishseal
4.Why ozone layer is called radiation belt?
Ans. Because it checks the entry of high energy UV-radiations of sunlight in the earth’s atmosphere.
5.What is detritus?
Ans. Dead organic matter.
6.Explain why the practice of serving tea in Kulhads (disposable cups made of clay) on trains has been discontinued.
Ans. Because the use of a lot of clay for making millions of Kulhads daily lead to the loss of fertile top soil in the fields.
7.Write the full form of CFC. Give its one harmful effect.
Ans. The full form of CFC is Chloroflouro-carbons. Chloroflouro carbons are damaging the ozone layer in the upper atmosphere.
SAQ (2 marks)
1.How is the ozone formed?
Ans. Ozone is formed high up in atmosphere by the action of ultraviolet radiation on oxygen gas as follows.
O2 O + O
O2 + O O3 (ozone molecule)
Oxygen molecule.
2.State any two practices which can help in the protection of our environment.
Ans. i. Disposal of waste after its separation as biodegradable and non-biodegradable waste material
ii. Judicious use of unleaded petrol, alternate sources of energy. Engines of vehicles should also be properly tuned and serviced so that vehicles run efficiently.
3.Give two ways in which biodegradable substance would affect the environment.
Ans. i. Stink- Within a day or so waste biodegradable substances begin to stink and produce foul gases.
` ii. Pests and Pathogens- the decaying biodegradable substances become breeding places of many pests. Because of being waste in origin they often contain pathogens.
4.Which of the following are biodegradable and which non-biodegradable?
Glass bottle, Paper, Ball point pen refill, DDT, Wheat, Cake, Wood, Polythene bag, Cotton, Grass, Vegetable peels.
Ans. i. Biodegradable: Paper, Wheat, Cake, Wood, Jute bag, Cotton Cloth, Grass, Vegetable peels.
ii. Non- biodegradable: Glass bottle, Ballpoint pen refill, DDT, Polythene bag.
5.What is ‘Ten percent low’?
Ans. Ten percent low is an enunciation given by Lindeman (1942) that states that only 10% of energy contained in a lower tropic level, the remaining 90% being lost in transfer and respiration of the later.
SAQ (3 marks )
1.How is solar energy introduced into the ecosystem?
Ans. The green plants have a mechanism for trapping solar energy with the help of their green pigment called chlorophyll. The green plants after trapping the solar energy, convert it into chemical energy whish is stored as carbohydrates in the plants. Thus the initial point where energy from the environment enters into the living components of ecosystem (like plants and animals) is the process of preparation of food by green plants through photosynthesis.
2.How can you help in reducing the problems of waste disposal?
Ans. 1. Recycling of wastes.
2. Reduction at source.
3. Better management.
4. Vermi-composting.
` 5. Use of eco friendly products such as disposable paper cups in place of plastic cups,
Chapter 16
Management of Natural Resource
VASQ(1 marks)
1. Write utility of construction of dam and reservation.
Ans. Regular supply of water for irrigation, controlling floods and generating electricity.
2. Define biodiversity.
Ans. It refers to totality of genes, species and ecosystem of a region, eg -Forest.
3. Why was Ganga Action plan launched?
Ans. To restore quality of water in the Ganga. It was very poor due to pollution.
4. What are the three R’s to save environment?
Ans. Reduce, Recycle and Reuse.
5.The presence of which organism indicates the pollution index of water body?
Ans. The presence of coli form group of bacteria indicates the pollution index of water body.
6. Name the river with which Sardar Sarovar Dam is associated.
Ans. The river with which Sardar Sarovar Dam is associated is Narmada.
7. Give one criticism about large dam.
Ans. Large dams consume large amount of public money without the generation of proportionate benefits.
SAQ(2 marks)
1. Mention two ways in which water harvesting can be undertaken.
Ans. i. Capturing sum off water from roof-tops.
ii. Capturing sum off water from local catchments.
2. Why reuse better than recycling?
Ans. Reuse is better than recycling because the process of recycling uses some energy. In the reuse strategy we simply use things again and again.
3. What would be advantages of exploring resources with short terms aims?
Ans. Exploring resources with short-term aims provide immediate advantage that meet current basic human need.
4. How can you as an individual contribute or make a difference to management of (i) water resources and (ii) Coal and petroleum?
Ans.(i) Running water will not be used for brushing teeth or taking bath. Water will be taken in a mug and bucket for these purpose to prevent wastage.
(ii) Switch off unnecessary lights and fans etc. and use bicycle to cover short distances instead of a scooter or car.
5. Write down any two consequences of deforestation.
Ans. i. Change in climate and global warming
ii. Soil erosion and floods.
6. Name any two endangered plant and animal species.
Ans. Endangered plant species- Pitcher Plant and Snow orchid.
Endangered animal species- Indian wild Ass and Great Indian Rhinoceros
SAQ ( 3marks)
1. Can you suggest some changes in yours school whish would make it environment friendly?
Ans. i. School busses should be run on CNG instead of diesel.
ii. Trees should be planted along the school boundary.
iii. The fallen leaves of trees should be collected and made into compost. This compost can be used in school garden.
2. What are the causes of pollution of Ganga river?
Ans. 1. Dumping of garbage and untreated swage from all the towns and cities on the banks of the ricer.
ii. Bathing by millions of people, washing clothes, animals and vehicles in the river water.
iii. Immersion of ashes or even dead bodies in the performance of rituals.
iv. Releasing chemical effluents from industries directly into the river water.
3. Find out the traditional system of water-harvesting/ management.
Ans. Traditional system of water harvesting/ management.
i. Diversion of water flowing in streams into man made channels to cater to the demand of the people
ii. Collection of water in ponds.
iii. Contraction of dams.
4. Why is dependence of man or nature greater than that of any other organism?
Ans. Man’s dependence on nature is greater than that of any other organism because he:
i.Has developed curiosity for more comforts and security.
ii.Consumes large amount of material and energy.
iii.Has developed a new bond of socio-economic environment which consists of things developed by man through his tools and techniques.
5.What is Chipko Andolan?
Ans. This movement was launched by people of Reni in Garhwal. It was spearheaded by Sundar Lal Bahuguna. The Chipko Andolan (Hug the trees Movement) was the result of a grass- root level effort to end the alienation of people from their forests. The movement originated from an incident in a remote village called Reni in Garhwal during the early 1970’s The women of the village reached the forest and clasped the tree trunks to trees and felling it. Thus thwarted the constructor had to withdraw.
Chemical Reactions and Equations
Q.1. What is the general name of substances which are added to fat & oil containing
food to prevent rancidity. (1 Mark)
Ans. Antioxidants
Q.2. Write balanced chemical equation for the reaction of barium chloride with
Aluminium sulphate. (1 Mark)
Ans. 3 BaCl2 + Al2 (SO4)3 3 BaSO4 +2AlCl3.
Q.3. Identify the substance that is oxidised and the substance that is reduced in the
following reaction. 4 Na+O2 2 Na2O (1 Mark)
Ans. Substance Oxidised Na
Substance reduced O2
Q.4. Why does the colour of copper sulphate solution fade when iron nail is dipped in
it. (2 Mark)
Ans. The solution changes into iron sulphate Fe+CuSO4 FeSO4 + Cu
Q.5. What happens when quick lime is added to water? Write the chemical equation.
Which type of reaction is it endothermic or exothermic? (2 Mark)
Ans. Calcium oxide reacts vigorously with water to produce slaked lime (Calciumm hydroxide)
CaO+H2O Ca (OH)2 +Heat energy. It is an exothermic reaction.
Q.6. Silver chloride turns grey when kept in sunlight. Write chemical equation for it.
What type of reaction is it? (2 Mark)
Ans. 2 Ag Cl Sunlight 2 Ag (S) + Cl2 (g). It is a decomposition reaction
where light energy is absorbed. So it is an endothermic reaction.
Q.7. What happens when potassium iodide solution is added to lead nitrate solution? Give equation of the reaction involved. What type of reaction is represented by this example? (3marks)
Ans. When potassium iodide solution is added to lead nitrate solution, then a yellow
precipitate of lead iodide is formed alongwith potassium nitrate solution
Pb(NO3)2 (aq) + 2KI (aq) PbI2 (S) + 2 KNO3 (aq)
This is an example of a double displacement reaction. It is also a precipitation
Reaction.
Q.8. When a green iron salt is heated strongly, its colour finally changes to black and the odour of burning sulphur is given out.
a)Name the iron salt.
b)Name the type of reaction that take place during the heating of iron salt.
c)Write a chemical equation for the reaction involved. (3 Marks)
Ans:- a) Ferrous Sulphate
b) Thermal decomposition
c) 2 FeSO4 (S) Heat Fe2O3(s) + SO2 (g) + SO3 (g)
(Ferrous sulphate) (ferric oxide)
Green Colored Reddish brown.
Q. 9. Which type are the following reactions?
a) NH4Cl NH3 + HCl.
b) Fe + CuSO4 Fe SO4 + Cu
c) Ag NO3 + NaCl AgCl + NaNO3
d) PbO2 + SO2 PbSO4
e) CaCO3 CaO +CO2 (5 Marks)
Ans. a) Thermal decomposition reaction
b) Displacement reaction
c) Double displacement reaction
d) Combination reaction.
e) Thermal decomposition reaction
Q.10. Write balanced chemical equations for the following reactions:-
(5 Marks)
a) Dilute Sulphuric acid is poured on zinc granules
b) Iron reacts with steam
c) Carbon dixide reacts with water in the process of photosynthesis
d) Limestone is heated strongly.
e) Silver chloride is kept in sunlight in a china dish.
a) Zn + H2SO4 ZnSO4 + H2.
b) 3 Fe + 4H2O Fe3O4 + 4 H2
c) 6CO2 + 6H2O Sunlight C6H12O6 +6O2
d) CaCo3 Heat Chlorophyll CaO +Co2
e) 2 Ag Cl 2 Ag + Cl2
Chapter 2
Acids, Bases & Salts
1. How is the concentration of hydronium ion (H3O+) affected when a solution of an
acid is diluted? (1 Mark)
Ans. The concentration of hydronium ions, decreases when a solution of an acid is
Diluted.
2. Fresh milk has a PH of 6. How do you think the PH will change as it turns into curd? (1 Mark)
Ans. Its PH will decrease due to the production of lactic acid which is acidic in nature.
3. What is the PH of acid rains? ( 1 Mark )
Ans. Less than 5.6
4. Tooth enamel is one of the hardest substances in our body. How does it undergo
damage due to eating chocolates & sweets. What should we do to prevent it ?. ( 2 marks )
Ans. The bacteria present in mouth produce acids by the degradation of sugar & food
particles present in the mouth after eating. The acid so produced corrodes tooth
Enamel (Ca3(PO4)2). In order to prevent tooth decay we should clean the mouth
after eating food & we should use alkaline tooth paste.
5. Explain why for diluting an acid concentrated acid is added to water & not water to concentrated acid ?
Ans. This is because the process of dissolution of an acid in water is highly exothermic
process. For dilution the acid must be added slowly to water with constant stirring.
If water is added to acid, the heat generated may cause the mixture to splash out and cause burns. The glass container may also break due to excessive local heating.
6. A house wife found that the cake prepared by her is hard and small in size. Which
ingredients has she forgotten to add that would have made the cake fluffy? Give
reason.
Ans. She has forgotten to add baking powder. When baking powder is added [Sodium bicarbonate and tartaric acid mixture] during the preparation of cake and heated then
sodium bicarbonate reacts with tartaric acid to form CO2 gas. This CO2 evolved
makes the cake to rise and become light and fluffy. Since the cake prepared by the
house wife is small and hard, it means that she had forgotten to add baking
powder.
Q.7. You have been provided with three test tubes. One of them contains distilled water
and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, have will you identify the contents of each test
tube?
Ans. Dip red litmus paper in solution repeatedly in each tube.
(a)The tube in which the red litmus paper turns purple contains distilled water.
(b)The tube in which red litmus paper turns blue contains basic solution.
(c)The tube in which red litmus paper remains red contains acidic solution.
Q.8. Do basic solutions also have H+ (aq) ions? If yes, then why are these basic? What is an alkali ? (3 Marks)
Ans: Basic solutions also contain H+ (aq) ions. But in basic solutions:
[H+] <> 10-7 M
Since (OH-aq) is more than [H+aq]hence these are basic solutions.
Bases that are soluble in water are called alkalis. For example NaOH, KOH, Ca(OH)2
Q. 9. What is neutralization reaction? Write 3 applications of neutralization reaction.
Ans. Neutralization it is an interaction of an acid with a base to form salt and water.
e.g. HCI + NaOH NaCl + H2 O
Acid Base Salt Water
Q. 10. Application :(i) Antacids neutralize the excess acids in our stomach and relieve us
from pain Ex-magnesium hydroxide (milk of magnesia).
(ii) If the pH of the sail is less than 7 i.e. it is acidic, the farmer will treat the soil
with quick time, slaked time, chalk etc to neutralize the acidity.
(iii) Bee sting contains methanoic acid which causes pain and irritation. Use of
mild base. Ex baking soda neutralizes it.
Q 10. a) How do metal carbonates and metal hydrogen carbonates react with acids?
Explain with the help of an activity.
(b) What happens when sulphuric acid in rain reacts with calcium carbonate in buildings
Made from limestone? (5marks)
Ans. (a) All metal carbonates and hydrogen carbonates react with acids to form a
corresponding salt, carbon dioxide & water.
Metal Carbonate + Acid -> Salt + Carbon dioxide + water
Metal hydrogencarbonate + Acid -> Salt + Carbon dioxide + Water.
For ex, Sodium carbonate reacts with dilute hydrochloric acid as follows:-
Na2CO3 (S) + 2 HCI (aq) -> 2 NaCI (aq + H20 (l) + CO2 (g)
Sodium hydrogen carbonate reacts with dilute hydrochloric acid as follows:-
NaHCO3 (S) + HCI (aq) -> NaCI (aq) + H2O(l) + C02 (g)
Activity :- Text book page number 20 Activity 2.5
Observation:- CO2 is produced with an effervescence. When this gas is allowed to
pass through lime water it becomes cloudy. It is a test for CO2.
b) When sulphuric acid in rain reacts with calcium carbonate in buildings made
from limestone calcium sulphate and Carbon dioxide is produced.
CaCO3 + H2SO4 -> CaSO4 + CO2 + H2O.
Chapter -3
Metals & Non-Metals
Q.1. What would happen to a copper vessel if it is left for a few days in humid
atmosphere without being cleaned ? (1)
Ans:- The surface will get corroded with the formation of a green layer of copper
carbonate.
Q.2. Why is ZnO Called an amphoteric oxide? Show with the help an equation.
Ans. ZnO is called an amphoteric oxide because it shows both acidic as well as basic
behaviour, i.e., it reacts with both acids (eg. HCl) as well as bases(Eg. NaOH) to form salt & water.
ZnO + 2HCl -> ZnCl2 + H2O
ZnO + 2 NaOH -> Na2 ZnO2 + H2O
Q.3. Write the chemical equation for the reaction of hot aluminium with steam.
Ans. 2 Al + 3 H2O -> Al2O3+ 3H2
Q4. An element reacts with oxygen to form an oxide which dissolves in dilute HCl. The
Oxide also turns a solution of red litmus blue. Is the element a metal or a non-metal?
Explain with help of a suitable example.
Ans. The element is a metal. Taking the example of Na Metal, its oxide will be Na2O . It
dissolves dilute HCI as follows:
Na2O + 2 HCI -> 2NaCl + H2O
Na2O as well as all other metal oxides are basic. For example, Na2O is basic as it dissolves in water to form NaOH which is a base. Basic oxides turn red litmus blue.
Q.5. Give reasons for the following:
(i) Carbon is not used for making aluminium from aluminium oxide.
(ii) Al easily combine with oxygen but still can be used for making kitchen utensils. (2)
Ans. (i) Carbon is not used for making aluminium from aluminium oxide because
aluminium has greater affinity to oxygen than for carbon. Hence carbon cannot
reduce aluminium oxide to aluminium.
(ii)Aluminium easily combines with 02 to form a layer of aluminium oxide. This layer, however, acts as a protective layer and doesn’t allow the metal underneath to react further.
Q.6. What is activity series of metals? Arrange Al, Zn, and Mg. in an increasing order of reactivity. (2)
Ans. The arrangement of metals in order of their decreasing reactivity with respect to other is called activity series of metals. The increasing order of the given metals is: Hg <> Zn SO4 + Cu
(iii) Reaction of metals with HNO3 doesn’t evolve H2 gas. It is because HNO3 is a strong oxidizing agent. It oxidizes H2 produced to water and is itself reduced to any of its oxides such as N20. NO. or NO2.
Q8. Write chemical equations for the reactions taking place when
i)Zinc carbonate is calcined
ii)Cinnabar (HgS) is heated in the air.
iii)Manganese dioxide is heated with aluminium powder. ( 3 )
Ans. i) Zn CO3 (S) Calcination ZnO (S) + CO2 (g)
ii) 2HgS (S) + 302 (g) Heat 2HgO (S) + 2SO2 (g)
2HgO-> 2Hg (l) + O2 (g)
iv)3MnO2 + 4 Al. Heat 2Al2O3 + 3 Mn.
Q. 9. a) What is ionic bond?
b) How ionic bond is formed?
c) Write the formation of magnesium chloride. (5)
Ans. (a) The Chemical bond found by the transfer of electrons from one atom to another
is known as an ionic bond.
(b)An ionic bond is formed when one of the atoms can donate electrons to achieve the inert gas electronic configuration and other atoms need electrons to achieve the inert gas electronic configuration. When a metal (Usually 1, 2 or 3 electrons in outermost shell) reacts with a non-metal (usually 5, 6 or 7 electron in outermost shell), transfer of electrons takes place from metal atoms to the non-metal atoms and an ionic bond is formed.
(c)Formation of magnesium chloride (MgCl2). The atomic number of magnesium is 12. it has two electrons in its valence shell as shown below:
12 Mg – 2, 8, 2
Magnesium, therefore, has a tendency to lose the 2 valence electrons and in the
process attains the electronic configuration of neon
Mg-> Mg 2+ + 2e-
2, 8, 2 2,8
Chlorine (atomic number 17 ) has 7 electrons in the valence shell. It has a tendency to gain one electron to complete its octet.
Cl + e- Cl-
2,8,7 2,8,8
Thus, when magnesium and chlorine are brought together, the magnesium atom transfers its two valence electrons to two chlorine atoms. In the process both the atoms acquire the stable electronic configuration of nearest inert gases. The positively charged magnesium ion Mg2+ and negatively charged Chloride ions (Cl-) are now held together by the electrostatic force of attraction.
‾
Mg2+ + 2 Cl- Mg2+ 2 Cl- or MgCl2
This process can also be shown as below
(Mg 2+) [ ] 2 Mg xx
Q. 10. What is the difference between alloy & amalgam? Write the composition of brass & bronze. Write 2 properties of alloy. (5)
Ans. (a) Alloy – It is a homogeneous mixture of 2 or more metals or a metal and a non-metal.
Amalgam – If in an alloy one of the metals is mercury, then the alloy is an amalgam.
(b) Brass – Alloy of Copper and Zinc.
Bronze – Alloy of Copper and tin.
(c) Properties of alloy – (i) The electrical conductivity and melting point of an alloy is
less than that of pure metal.
(ii) Alloy does not corrode easily.
CHAPTER-4
Carbon and its Compounds
Q1. What is denatured alcohol? (1)
Ans:- Ethane is made unfit for drinking by adding poisonous substances like methane to it. Dyes are also added to colour the alcohol blue so that it can be identified easily. This is called denatured alcohol.
Q2. Name the product other than water formed on burning of ethanol in air? (1)
Ans:- Carbon dioxide gas.
Q3. Give the names of the functional groups: (1)
a) CHO b) C
Ans:- a) Aldehyde b) Ketone.
Q4. Why carbon forms compounds by sharing of electrons and not by formation of ions? ( 2)
Ans:- Carbon is tetravalent in nature. If it gains 4 electrons to form C 4- ions, then it will be difficult for 6 protons to hold on to 10 electrons.
To lose 4 electrons forming C4 + ion, it would require a large amount of energy to remove 4 electrons. Hence it forms bond by sharing of electrons.
Q5.Allotropy is a property shown by which class of substances: elements, compounds or mixtures? Give one example of allotropy. ( 2)
Ans. Elements show allotropy. For example, graphite, diamond and fullerenes are allotropic forms of carbon.
Q6. Under what conditions can a saturated hydrocarbon produce a sooty flame? (2)
Ans. Saturated hydrocarbon produce sooty flame only when burnt in limited supply of oxygen.Due to limited supply of oxygen, the incomplete combustion of the hydrocarbon takes place resulting in unburnt carbon producing sooty flame.
Q7.a) Draw the structure for the following compounds: (3)
i)Propanoic acid.
ii)Butanal
b) Why is conversion of ethanol acid considered as oxidation reaction?
ANS. a) H H O
H C C C OH
H H
Propanoic acid
H H H H
H C C C C = 0
H H H
Butanal
b) Ethanol is oxidised with alkaline potassium permanganate to form ethanoic acid. As the addition of oxygen takes place,therefore it is called oxidation reaction.
Q8. What happens when an ester is heated with a base such as sodium hydroxide? Write equation of the reaction which takes place? What is the special name for this reaction and for what purpose it is used? (3)
Ans. When an ester is heated with sodium hydroxide solution then the ester gets hydrolysed to form the parent alcohol and sodium salt of the carboxylic acid .
Example---When ethyl ethanoate ester is boiled with sodium hydroxide solution, then sodium eyhanoate and ethanol are produced.
CH3COOC2H5 + NaOH ---------CH3COONa + C2H5OH
Sodium Ethanol
Ethanoate
The alkaline hydrolysis of esters is known as saponification (soap making).This is because of the fact that this reaction is used for the preparation of soaps. When the esters of higher fatty acids with glycerol (oils and fats) are hydrolysed with sodium hydroxide solution,we get sodium salt of higher fatty acids which are called soaps.
.
Q9 a)What is the difference between soap and detergent in chemical composition ?
b)Why detergent remains effective in hard water while soap not for cleaning?
c)Explain the mechanism of the cleaning action of soap. (5)
Answer:- a) Soap:- It is sodium or potassium salts of long chain carboxylic acid.
Detergent:- It is ammonium or sulphonate salts of long chain carboxylic acids.
b) Soap reacts with calcium and magnesium chloride or sulphate which causes hardness of water to form an insoluble substance (scum). The charged ends of detergents donot form insoluble precipitates with the calcium and magnesium ions in hard water. Thus, they remain effective in hardwater.
c) Most dirt is oily in nature. Oil does not dissolve in water. The molecule of soap has two ends with differing properties. The ionic-end of soap dissolves in water while the carbon chain dissolves in oil. The soap molecules, thus form structures called micelles where one end of the molecule is towards the oil droplet while the ionic end faces outside. This forms an emulsion in water. The soap micelles thus helps in dissolving the dirt in water and we can wash our clothes clean.
10) Write the chemical equation for the following reaction:
a) Ethanoic acid with Sodium Carbonate
b) Ethanoic acid with Sodium Bicarbonate
c)Burning of Ethanol
d)Ethanoic acid with Sodiun Hydroxide
e) Heating Ethanol at 443K with excess concentrated sulphuric acid (5)
Anwser:- a)2CH3COOH + Na2Co3 2CH3COONa + H2O + CO2
b) CH3COOH + NaHCO3 CH3COONa + H2O + CO2
c)CH3CH2OH + O2 CO2 + H2O + heat and light
d) NaOH + CH3COOH CH3 COONa + H2O
Hot conc.
e) CH3 CH2OH CH2 = CH2 + H2O
H2SO4
5. PERIODIC CLASSIFICATION OF ELEMENTS
Q.1.What were the criteria used by Mendeleyev in creating his periodic table?
Ans.In creating his periodic table, Mendeleev was guided by two factors:-
(a). Increasing atomic masses and;
(b) Grouping together of elements having similar properties.
Q.2.Besides Gallium, which other elements have since been discovered that fill the gaps left by Mendeleev in this periodic table?
Ans.Scandium and Germanium.
Q.3.Name two elements you would expect to show same kind of chemical reactivity as Magnesium. What is your best choice?
Ans.Beryllium, Calcium and Strontium will show same kind of chemical reactivity as Magnesium because they are placed in the same group. Elements placed in the same group have similar outer electronic configuration.
Q.4.Looking at the resemblance of Hydrogen to alkali metals and the Halogen family, to which group and period should Hydrogen be assigned in Mendeleev’s periodic table?
Ans.Since properties of Hydrogen resemble both alkali metals and Halogens, it can be placed either in group IA or group VII A. Since Hydrogen has the lowest atomic mass, it is placed in period I.
Q.5.An atom has electronic configuration 2, 8, 7.
(a) What is the atomic number of this element?
(b) To which of the following elements would it be chemically similar:-
(i) 7N
(ii) 9F
(iii)15P
(iv)18Ar
Ans. (a) The atomic number of the element is 2+ 8+7=17.
(b) Electronic configurations of the given elements are:-
(i)N-2,5.
(ii)F-2,7.
(iii)P-2,8,5.
(iv)Ar-2,8,8.
Thus F having similar electronic configuration with 7 valence electrons would be chemically similar to the given element.
Q.6.The positions of three elements A, B, C in the periodic table are show below:-
Group 16 Group 17
- -
- A
- -
B C
(a) State whether C is a metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller than B in size?
(c) Which type of ion (cation or anion) will be formed by element A?
Ans.(a) Elements of group 17 have 7 electrons in their respective valence shell and have a strong tendency to gain an electron to complete their octet. So, A is a non-metal.
(b) On moving down a group, the atomic size increases and thus the force of attraction of the nucleus for the incoming electrons decreases. Hence the reactivity decreases. Therefore C is less reactive than A.
(c) B and C belong to the same period. On going from left to right in a period the nuclear charge increases but the number of shells remain same. Therefore atomic size decreases from left to right. Thus C is smaller in size than B.
Q.7.Use Mendeleev’s periodic table to predict the formulae for the oxides of K, C, Al, Si and Ba.
Ans.K2O, CO2, Al2O3, SiO2, BaO.
Q.8.A metal M forms an oxide having the formula M2O3. It belongs to third period of the modern periodic table. Give its atomic number and valency.
Ans.Atomic number of the element is 2, 8, 3=13 and its valency is 3.
Q.9.What are the uses of Modern Periodic table?
Ans.In modern periodic table, the elements with similar properties are placed together in the same group. If we know the properties of one element of the group, the properties of other elements of the group can be predicted. Thus it makes the study of elements systematic.
Q.10.Why is long form periodic table regarded better than Mendeleev’s periodic table?
Ans.It is due to the following reasons:-
(a)It is based on atomic number.
(b)There is no confusion regarding the position of isotopes.
(c)All groups are independent and there are no sub-groups.
(d)It is more systematic.
Chapter 6
Life Processes
VSA Question carrying 1 marks each
Q1. What are the main two types of nutrition?
Ans. Autotrophic and Hetrotrophic nutrition.
Q2. what does the word ‘Sapro’ mean?
Ans. The word Sapro means rotten.
Q3. What is the process of obtaining food in Amoeba called?
Ans. The process of obtaining food in Amoeba is called Phagocytes.
Q4. name the cellular organelles where the folloing processes take place (i) Photo synthesis (ii) Cellular aerobic respiration?
Ans. (i) Chloroplast (ii) Mitochondria.
Q5. What is the function of bile?
Ans. Bile brings about the emulsification of fats.
Q6. Where are hormones synthesized in plants?
Ans. In planyts hormones are synthesized in the shoot and root tips.
Q7. Name the largest artery in our body?
Ans. Aorta
Q8. What is the liquid part of blood called?
Ans. Plasma.
SAQ carrying 2 marks each.
Q1. What is emulsification?
Ans. Breakdown of the large fat droplets into smaller ones.
Q2. Why are plants green?
Ans. Plants posses green chloplastic pigments called chlorophyll which absorb most of the blue and red regions of the incident light. They reflect green light so the plants look green in colours.
Q3. State the function of epiglottis?
Ans. Epiglottis is a leaf like cartilaginous flap present at the anterior end of glottis. It closes the glottis during swallowing to check the entry of food into glottis.
Q4. In which form is (i) Carbohydrates stored in plants (ii)Food stored in animals.
Ans. (i) Carbohydrates are stored in the form of starch in plants.
(ii) In animals food is stored in the form of glycogen.
Q5. What is breathing?
Ans. It is aphysical process of inhalation or bringing in fresh air for obtaining oxygen and exhalation or taking out of foul air for elimination of CO2.
SAQ carrying 3 marks each.
Q1. Why are white blood corpulses called “Soldiers” of the body?
Ans. White blood corpulses are called soldiers of the body because they protect the body from infections by destroying foreign matter. They also manufacture antibodies which are responsible for immunity.
Q2. What happens to glucose which enters nephron along with filtrate during excretion in human beings. State two vital functions of kidney.
Ans. Glucose is reabsorbed in tubule.
Vital functions of kidney (i) Excreation, separation of nitrogenous wastes for elimination.
(ii) Osmoregulation, maintainance of balance of water and salts in the body through elimination if extra and retention if deficient.
Q3. When is blood clotting useful?
Ans. Cloting of blood is useful phenomenon to stop flowing of blood (bleeding) during cuts and accidents and at the time of accidents.
Q4. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Ans. Mammals and birds are warm blooded animals. They continiously use energy to maintain treir body temperature. They have a higher energy need and require more oxygenated blood for their cells. It is important that their oxygenated blood doesnot mixup with deoxygenated blood.
Long Answer Question carrying 5 marks.
Q1. Name the blood vessel that brings deoxygenated blood to the human heart (b) Which chamber of human heart receives oxygenated blood (c) Explain how oxygenated blood from this chamber is sent to all parts of the body?
Ans. (a) Pulmonary vein.
(b) Left arterium.
(c) After receiving the deoxygenated blood, the atium contract during this countraction the deoxygenated blood of the right atium is poured into the right ventricle. Then the ventricle contract and the deoxygenated blood flows to the lungs through pulmonary artery.
CHAPTER 7
CONTROL AND COORDINATION
Q1 Which gland secretes the growth hormone? (1)
Ans Pituitary gland (anterior lobe of pituitary).
Q2 Name the part of the hindbrain which is responsible for maintaining the posture and balance of the body. (1)
Ans Cerebellum.
Q3 Which hormone is responsible for the development of moustache and beard
in man ?
Ans Testosterone
Q4 Why is the use of iodised salt advisable ? (2)
Ans Iodine is essential for the synthesis of thyroxin hormone in the thyroid gland.
Thyroxin regulates carbohydrates , protein and fat metabolism in the body so
. as to provide the best balance for growth .In case of deficiency of iodine in
our diet , there is a possibility that we might suffer from goitre . Thus , use
of iodised salt is advisable to prevent iodine deficiency in the body .
Q5 Why are diabetic patients advised to take less sugar in their diet by the
doctor ? (2)
Ans Insulin hormone is secreted by the pancreas which helps in regulating blood
sugar level in our body .It is not secreted in proper amount in the body of
the diabetic patient. If the sugar level in the blood rises , it causes many
harmful effects . So the diabetic patients are advised to take less sugar .
Q6. What happens at the synapse between two neurons ? (2)
Ans. The information acquired at the end of the dendrite tip of a nerve cell sets
of a chemical reaction that creates an electrical impulse This impulse travels from the dendrite to the cell body , and then along the axon to its end .At
the end of the axon , the electrical impulse sets off the release of some
chemicals . These chemicals cross the gap or synapse and start a similar
electrical impulse in a dendrite of the next neuron .
Q7. What is the difference between sensory and motor neurons? Which part of the brain
is responsible for auditory reception and sensation of smell? (3)
Ans. Sensory neurons-These are the neurons that transmit impulses towards the central
nervous system (brain and spinal chord) through their axons.
Motor neurons- These are the neurons that transmit impulses from central nervous
system towards effectors (muscles or glands).
Specific part of brain is responsible for auditory reception and smell.
Q8 Draw a human brain and label its different parts? (3)
Ans Text book page no.118 & fig.7.3.
Q9 What is a reflex action? Explain with help of an example. Draw a labeled diagram
to show the reflex action? (5)
Ans a) Reflex action is spontaneous & involuntary response of effectors (muscles &
glands) to stimulus. It is extremely quick action that does not involve any thinking
by the brain.
b) When our hand accidentally touches the hot object, heat is sensed by the thermo receptors present in the skin of hand. The receptor triggers nerve impulse in sensory neuron. It transmits message to spinal cord. In spinal cord impulse is passed on to the relay neuron which ,in turn passes it to the motor neuron. The motor neuron transmits the instruction to a muscle in our arm. The arm muscles contract and pulls our hand away from the hot object.
c) Text book page no.117 fig7.2
Q10. a)How is the movement of leaves of a sensitive plant different from the movement of the shoot towards light? 5)
b)Name one plant hormone that promotes growth in plant and one plant hormone that inhibits growth?
c)How does phototropism occur in stem?
Ans a) The movement of leaves of a sensitive plant is neither towards nor away from stimulus like touch. While movement of shoot is towards stimulus like light .The movement of leaves of a sensitive plant is not directional while the movement of shoot is directional.
b)Plant hormone that promotes growth in plants-Auxin
Plant hormone that inhibits growth-Abscisic acid.
c)The movement of a plant part in response to light is called phototropism.
The shoot responds by bending towards light while roots respond by bending away from the light. We know that the plant stem responds to light and bends towards it due the action of auxin hormone.This happens as follows:
i)When sunlight comes from above, then the auxin hormone present in the tip of the stem spreads uniformly down the stem .Due to the equal presence of auxin, both the sides of the stem grow straight and with some rapidity.
ii)When the light falls on the right side of the plant, then the auxin hormone collects in the left side of the stem, away from the light. This is because auxin hormone prefers to stay in shade.
Thus more auxin hormone is present in the left side of the stem as compared to the right. The left side of stem, hence grows faster than its right side and therefore, the stem bends towards the right side (direction of light).
8.
Q1 Name any two sexually transmitted diseases?
Ans: 1] Gonorrhoea 2] syphilis
Q2 Write full form of IUCD and AIDS?
Ans: IUCD-Intra Uterine Contraceptive Device.
AIDS-Acquired Immuno Deficiency syndrome.
Q3 Where does fertilization take place in human female?
Ans: Fertilization takes place inside the fallopian tubes.
Q4 If a women is using Copper-T, will it help her in protecting sexually transmitted diseases?
Ans: Copper-T prevents fertilization but the chances of infection persist. So, Copper-T will not help her in protection against sexually transmitted diseases.
Q5 What are the advantages of sexual reproduction over asexual reproduction?
Ans: Due to reshuffling of chromosomes and crossing over, sexual reproduction brings about variation in almost all characters so that no two individuals are similar. Genetic changes contribute to evolution of species to form better organisms. Asexual reproduction does not contribute to evolution of species as there is no variation.
Q6 Why is vegetative propagation practiced for growing some type of plants?
Ans: Vegetative propagation is practiced in some plants because-
1.It is the only method of reproduction in seedless plants.
2.A full matured plant is obtained in a very short time.
3.It helps to preserve the characters of the plant the breeder desires.
4.It is an easy and economical method for multiplication of ornamental plants.
Q7 How does reproduction helps in providing stability to population of species?
Ans: Reproduction helps in providing stability to population by-
1.Introducing variation in the population through genetic combination that helps the population to tide over adverse environmental conditions and adapt to changing environment.
2.Balancing birth and death rate.
Q8 What could be the reasons for adopting contraceptive methods?
Ans: Contraceptive methods are adopted for the following purposes-
1.To avoid frequent and unwanted pregnancies.
2.To maintain good reproduction health.
3.To obtain protection from sexually transmitted diseases.
4.To restrict the number of children.
Q9 Differentiate between menarche and menopause?
Ans- Commencement of menstruation at puberty in human female is termed menarche and its stoppage at the age of 50yrs is called menopause.
Q10 What is the importance of DNA copying in reproduction?
Ans-DNA copying is an important phenomenon of reproduction through which the organisms pass their features to their offsprings. It maintains the genetic pool and the body design features in different generation of the species. DNA copying also produces variations due to genetic linkage and crossing over of chromosomes. Such variations are useful for the survival of species.
9.
Q1:-Give examples of two variations found in humans.
Ans: - 1. Human height
2. Free earlobe and attached earlobe
Q2:- Write the names of the components of DNA?
Ans: - Components of DNA are nucleotides. Each nucleotide has further three components-
1.Deoxyribose sugar
2.A nitrogenous base
3.A phosphate group
Q3:-Give two examples where environmental factors govern sex-determination?
Ans: - a) In turtle, high incubation temperature results in the development of female progeny.
b) In lizard high incubation temperature results in male progeny.
Q4:- What is genetic engineering? Give the full form of GMO.
Ans: - It is the technique of altering the genetic make up of an organism by inserting gene (or segment of DNA) from other organism into its DNA.
The full form of GMO is GENETICALLY MODIFIED ORGANISM.
Q5:- How are the areas of study – evolution and classification interlinked?
Ans:-Classification of organisms is based on relative similarities and differences among organisms. Resemblances in organisms are because they have arisen from a common ancestor and differences are due to adaptations to different types of environment. As the organisms can be graded in order of increasing complexity, it indicates the concept evolution.
Q6:-Why are small numbers of surviving tigers a cause worry from the point of view from genetics?
Ans: - With decreasing number of tigers, their genetic pool is also vanishing which is essential to maintain the ecological and food chain balance.
Q7: - Will geological isolation be a major factor in the speciation of an organism that reproduces asexually? Why or Why not?
Ans: -During asexual reproduction organisms undergo a little variation over generations .The variation in the genetic pool are not enough to raise a new species .Thus, any change resulting from geographical isolation may not be passed to the next generation.
Q7: -A man with blood group ‘A’ marries a women blood group ‘O’ and their daughter has blood group ‘O’. Is this information enough to tell you which of the traits –blood group ‘A’ or ‘O’ is dominant? Why or Why not?
Ans: - Blood group ‘A’ is dominant while ‘O’ is recessive character. If a man with blood group ‘A’ marries a woman with blood group ‘O’ and their daughter has blood group ‘O’ , then the man has one copy of ‘A’ and one copy of ‘O’ blood group.
Q8: - Differentiate between autosomes and sex chromosomes.
Ans: - 1. The pair of chromosomes that are responsible for development of body characters are called autosomes .In human body, there 22 pairs of autosomes.
2.The pair of chromosomes which are responsible for determining the sex of the individual called sex chromosomes .
Q9: -Why Mendel selected garden pea plant for his experiment.
Ans: - Mendel selected garden pea plant for his experiment because-
1. Pure varieties of pea were available.
2. Pea plants showed a number of easily detectable contrasting characters.
3. The flower structure of pea is such that it allows controlled breeding.
4. Pea flower normally remains closed and undergoes self pollination.
Q10:-How is the equal genetic contribution of male and female parents ensured in the progeny?
Ans:-The gametes responsible for the formation of progeny develop by the process of meiosis. During meiosis only one set of chromosomes (50% of Gene) is transferred to the gamete. When male and female gametes fuse, one set of chromosome from each parent cell come together and complete the genetic pool.So, progeny receives 50% genetic contribution through each gamete(male and female).
10.LIGHT – REFLECTION AND REFRATION
Q1:- Define 1 dioptre of power of lens?
Ans: - One dioptre is the power of a lens of focal length one metre.
Q2:- Why do you prefer convex mirror as a rear-view mirror in vehicles?
Ans: - A convex mirror produces an erect and highly diminished image of the objects.Further, since it is curved outwards; it gives a wider field of view.
Q3:- The refractive index of diamond is 2.42.What is the meaning of the statement?
Ans: - It means that light travels 2.42 times faster in vacuum than in diamond.
Q4:- One half of a convex lens is covered with a black paper. Will this lens produce a complete image of that object? Verify your answer experimentally. Explain your observation.
Ans:- Yes ,it will produce a complete image of the object.
This can be verified experimentally by observing the image of the distant object like tree on a screen when lower half of the lens is covered with a black paper. However, the brightness of the image gets reduced.
Q5:- How can you distinguish between a convex mirror, a plane mirror and concave mirror?
Ans: - With the help of virtual image of three mirrors, we can distinguish between three mirrors-
a)Plane mirrors will produce virtual image of the same size.
b)Concave mirrors will produce magnified virtual image.
c)Convex mirror will produce a diminished virtual image.
Q6:- The magnification produced by a plane mirror is +1.What does this mean?
Ans:- m = h’/h=1
Therefore, h’ = h
i.e, the size of the image is equal to the size of the object. +ve sign of m indicates that the image is virtual.
Q7:- Calculate the distance at which an object should be place in front of a thin convex lens of focal length 10cm to obtain a virtual image of double its size?
Ans:- f = +10cm
m = +2 (as the image is virtual)
As, m = v/u = 2
Or, V = 2u
As, 1/v -1/u = 1/f
Or, 1/2u - 1/u = 1/10
Or, - 1/2u = 1/10
Therefore u = -5cm
The object should be place at a distance of -5cm from the lens.
Q8:- A concave mirror of focal length 20cm is to be used as a shaving mirror. Which of the following is the suitable object distance from the mirror? Justify your answer.
a)10cm
b)20cm
c)30cm
Ans:- For using concave mirror as shaving mirror, u
Ans:-
As, n = c/v
V = c/n
= 3 x (10)8/2.42
= 1.24 x 108 m/s
Q10:- A concave mirror of focal length 15cm forms an image of an object kept at a distance of 10cm from the mirror. Find the position, nature and size of the image formed by it.
Ans:- Here ,
f = -15cm
u=-10cm
v=?
1/v= 1/f -1/u (mirror formula)
1/v= 1/ (-15) -1/ (-10)
= 1/10 – 1/15
= 3/30 -2/30
=1/30
Therefore, v = 30cm
Thus, the image is formed at 30cm from the mirror.
As, v is positive, the image is virtual and erect
As, m = -v/u
= - 30/ (-10)
=3
Therefore, the size of the image is three times the size of the object.
11.HUMAN EYE AND COLOURFUL WORLD
Q1:- Name the optical phenomenon responsible for formation of RAINBOW?
Ans:- Refraction, internal reflection and dispersion of light.
Q2:- What is meant by scattering of light?
Ans:-Scattering is the bouncing off of electro-magnetic radiations by atoms and molecules of the medium through which they are propagating.
Q3:- Why different colours deviate through different angles on passing through a prism?
Ans:- This is because different colours have different wavelengths and glass has different refractive index for different wavelengths .
Q4:-Which phenomenon of vision is used in cinematography?
Ans:-Persistence of vision.
Q5:- The near point of the hypermetropic eye is 1metre.What is the power of the lens required to correct this defect. Assume that near point of the normal eye is 25cm.
Ans: - Since, the near point of the hypermetropic eye is1m (100cm), the lens used should be such that the rays of light starting from normal near point(25cm) appear to come from the near point of hypermetropic eye.
Thus,
u = -25cm
v =-100cm
1/f =1/v -1/u
f = uv/u-v
= (-25) x (-100)/ (-25) – (-100)
=100/3
=33.3cm
P = 100/f
= 100/33.3
= 3 D
Since the power is positive , lens must be convex.
Q6:-The far point of a myopic person is 80cm in front of the eye. What is the nature and power of the lens required to correct the problem?
Ans:- Distance of far point ,x =80cm
P =?
For viewing distant objects, focal length of the corrective lens
f = - x = -80cm
P = 100/f
= 100/-80
=-1.25 D
The Lens is concave.
Q7:- Danger Signals are red in colour, why?
Ans:-Due to its longer wavelength, red colour is least scattered by fog or smoke.Thus, the red is visible in the same colour from large distances.
Q.8.Why do we have two eyes for vision and not just one?
Ans. (a) It gives a wider field of view.
(b).The ability to detect faint objects is enhanced with two eyes instead of one.
(c). Our eyes are separated by a few centimeters; each eye sees a slightly different image. Our brain combines the two images into one and thus provides a three-dimensional perception of the objects.
Q.9.What is persistence of vision?
Ans.The ability of an eye to continue to see the image of an object for a very short duration even after the removal of the object is called persistence of the vision. In human eye, vision persists for 1/16th of a second after removal of the object.
Chapter 12
Electricity
V.S.A Question (1 mark each)
1.What is the resistance of an ideal voltmeter and an ammeter?
Ans. Infinite and zero.
2.What is the value of charge on an electron in coulomb?
Ans. -1.6 x 10-19
3.Why is resistance more in combination of resistors?
Ans. In series combination of resistors, the effective length of the conducting path increases and as such resistance increases (R ∞l)
4.Name two special characters of a heater coil?
Ans. A heater coil should have (i) high resistivity (ii) high melting point.
5.What is the resistance of a connecting wire?
Ans. It is negligible, almost zero.
S.A.Q (2 marks each)
1. What is the difference between a resistor and resistance?
Ans. A resistor is an object where as resistance is its property due to which it obstructs the flow of electrons through it.
2.Electric current is flowing through a wire from west to east direction. What is the direction of motion of the conductor electrons in the wire?
Ans. From east to west as direction of electric current is opposite to the direction of flow of conduction electrons.
3.Why are the conductors of electric heating devices such as toasters and electric irons) made of an alloy rather than a pure metal?
Ans. It is because alloy is less affected by the rise in temperature than a pure metal. In other words alloys do not oxidise (or burn) easily at high temperature.
4.What will be the equivalent resistance R of two resistors R1 and R2 (i) connected in series and (ii) connected in parallel?
Ans. When connected in series
R=R1+R2
When connected in parallel
1/R=1/R1+1/R2 or R=(R1R2) /(R1+R2)
5.What will happen to current if the voltage across the circuit reduces to half its original value while the resistance of the circuit remains constant?
Ans. Current=Voltage/Resistance
If voltage becomes half its original value, the resistance remains the same, then current in the circuit will be reduced to half its original value.
SAQ (3 marks each)
1.A wire of resistance 5 ohm is bent in the form of a closed circle. What is the effective resistance between the two points at the ends of any diameter of the circle?
Ans. The length of the wire between two points at the ends of a diameter of a circle is half of the whole wire. The resistance of a conductor is directly proportional to its length.
Thus, the two resistance 5/2 Ω will be in parallel.
Let R be the effective resistance.
1/R=2/5+2/5
1/R=4/5
R=5/4=1.25 Ω
2.Calculate the effective resistance in the diagram given.
Ans. In this case resistance DA and AB are in series. DC and CB are also in series. But AD and AB together are in parallel to DC and CB together.
Thus, Resistance (DA + AB)=1+1=2Ω
and Resistance (DC + AB)=1+1=2Ω
Let Rp be the effective resistance, then (by parallel formula)
1/Rp=1/2+1/2
=(1+1)/2=2/2
Rp=1Ω
Thus, the combination has a resistance of 1 ohm.
3.Why does resistance of a conductor increase with increase in temperature?
Ans. When a metallic is heated the atoms in the metal vibrate with greater amplitude and frequency due to increase in temperature the thermal velocities of free electrons also increase. Therefore the numbers of collisions between free electrons and atoms increase. This increases the resistance of the conductor.
4.Why is it not advisable to handle electrical circuit with wet hands?
Ans. The resistance of dry skin human body is about 50,000Ω. When the skin is wet, the resistance is lowered to about 10,000Ω. If a person with wet hand touches the electrical circuit the current will flow suddenly due to less resistance. Therefore, it is advisable not to touch the electrical circuit with wet hands.
Long Answer Question (5 marks)
1.A dry cell should be used intermittently and not continuously. Explain why?
Ans. Hydrogen gas in the formed during the working of the dry cell. This gas in the form of bubbles forms an insulated layer around the carbon rod (i.e anode). As a result of this, the resistance of the cell is increased and hence the flow of charges in the cell is opposed. Ultimately, the dry cell stops working if used continuously. However, these bubbles of hydrogen gas are removed slowly by Mno2, which acts depolarizers. The dry cell can work if the bubbles of hydrogen gas around carbon rod are completely removed by Mno2. For this purpose time is required. So the dry cell should be used intermittently to provide sufficient time for the removal of hydrogen gas bubbles by manganese dioxide.
13.Magnetic effect of electric current
V.S.A.Q (1 marks)
1. What constitute the field of a magnet?
Ans. The space around a magnet within which its magnetic effect can be experienced, constitutes the (magnetic) field of the magnet.
2. What is meant by the following? A fuse is rated at 8 A?
Ans. It means that it burn if current exceeds 8A.
3.What is short circuiting in an electric supply?
Ans. Short circuiting in an electric supply occurs when the live wire touches the neutral wire.
4.What happens when a current carrying conductor is kept in a magnetic field?
Ans. It experience a force.
5.Are magnetic field lines open or closed curves?
Ans. They are closed curves.
6. What is the frequency of AC in India?
Ans. It is 50 Hz.
SAQ (2 marks)
1.Write down any two properties of magnetic field lines.
Ans. 1 It is directed from north pole to south-pole outside the magnet and inside the magnet it is vice-versa.
2.Two magnetic field lines never intersect each other.
2. What is electro-magnetic induction?
Ans. In reality it is the conversion of mechanical energy into electrical energy.
3.What is the role of each of the three pins in a power plug?
Ans. The thick pin at the top of a power plug is for earthing ,the live pin is on the left and the neutral pin is on the right of the power plug.
4. what are the two main precautions to be the taken while using an electric supply?
Ans. (i)Electric supply should be immediately switched off from the main switch in case a person touches a live wire or if there is a fire in the house.
(ii) Electric supply should also be switched off during natural calamities like earthquake, floods etc.
5.What is the difference between two circuits used in household electricity?
Ans. One of 15 ampere rating is used for higher power appliances and second of 5 ampere rating is used for bulbs, fans, etc. which are of lower power rating.
6.Two wires A and B suspended. These wires are connected in parallel with a battery as shown in figure. Will the distance of separation between the wires (i) remains the same or (ii) increases or (iii) decreases? Explain.
Ans. When wires are connected to battery in parallel, then the current in both the wires will attract each other, therefore the distance between the wire decreases.
SAQ (3 marks)
1.A circuit has a fuser of 5 A. What is the maximum number of 100 watt (220v) bulbs this can be safely used in the circuit?
Ans. Suppose x number of such bulbs can be used.
Power of one bulb =100 watt
Power of x bulb (p)=100 x X watts
Potential difference(v)=220 volts.
I=5 ampere
P=VI
= 100 x X= 220x5
X =220x5/100=11 bulbs
2.On what factors does the force experienced by a current carrying conductor placed in a uniform magnetic field depend?
Ans. The place in a uniform magnetic field depends on :-
(i)The length of the conductors(l).
(ii)The magnitude of current flowing through the conductor (l), and
(iii)The magnitude of the magnetic field of the conductor (B)
3.A fixed wire AB carries current I. An electron is moving parallel to the wire in which direction does the electron tend to move?
Ans. By right hand thumb rule, the magnetic field in the vicinity of wire is downward, perpendicular to the plane of the paper. The conventional direction of electrical current his opposite to the direction of motion of electron. By Fleming left hand rule the force on electron is always away from wire in the plane of paper; therefore, the electron will be deflected downward (away from the wire) in the plane of paper.
4.A cylindrical bar magnet is kept along the axis of a circular coil. Will there be a current induced in the coil if the magnet is rotated about the axis?
Ans. The magnetic field of a cylindrical magnet his symmetrical about the axis. As the magnet is placed along the axis of circular coil, there will be no induced current because the magnetic flux linked with the coil does not change due to rotation of the magnet.
LAQ (5 marks)
1.Answer the following
i.What is the phenomenon of electron magnetic induction?
ii.Which is the device used for producing current?
iii.What is the essential difference between AC generator and a DC generator?
iv.At the time short circuit, what happens to the current in the circuit?
v.Give the role of split ring in AC generator?
Ans. i) the phenomenon of electromagnetic induction is producing induced current in a coil due to relative motion between a magnet and the coil.
ii) The device used for producing current is generator
iii) The essential difference between an AC generator and DC generator is that AC generator has slip rings while the DC generator has a commutator.
iv)At the time of short circuit, the current in the circuit increases heavily.
v)The role of split ring is to reverse the direction of current through a circuit.
14.Sources of Energy
VSAQ (1 marks)
1.Name the two forms of energy usually at our homes?
Ans. Heat and electricity
2.Exposure to which component of solar radiation could be a health hazard?
And. Ultra violet radiation.
3.Name two forms in which solar energy manifests itself in oceans?
Ans. Tidal energy and ocean thermal energy
4.What are the sources of energy in nuclear fission and fusion?
Ans. The disappearance of certain mass ( m) in both the processes, fission and fusion. It appears as energy.
5.Which radiations of sunlight are used in heating a solar cooker?
Ans. Infra red radiations.
6.Name any two renewable sources of energy?
Ans. Solar energy and Geo-Thermal energy.
SAQ(2 marks)
1.Give any two peaceful uses of nuclear energy.
Ans. Nuclear energy can be used:
(i)for generating electricity
(ii)in the treatment of cancer
2.How is electrical energy obtained from nuclear reactors?
Ans.The large amount of heat produced during nuclear fission is treated to convert into steam. The steam is then used to drive turbines which are connected to electrical generators which convert it into electrical energy.
3.What is the purpose of glass sheet in solar heating devices?
Ans. Glass sheet has a property that permit the infra-red radiations of short wave length from the sun to get into heating device but does not allow IR radiations of longer wave length to leave the solar heating device.
4.Why is the use of charcoal discouraged although it is a better fuel than coal?
Ans. Because charcoal is prepared from destructive distillation of wood. So, for this purpose more and more trees would have to be cut down which causes deforestation. It affects the ecological balance of earth.
5.Can any source of energy be pollution free? Why or why not?
Ans. No source of energy can be perfectly pollution free but biomass energy, hydroenergy, wind energy, geothermal energy and solar energy is almost pollution free. If fossil fuel is allowed to burn in presence of excess of oxygen the pollution produced can be much reduced.
SAQ (3 marks)
1.If you could use any source energy for heating your food, which one would you use and why?
Ans. Fuel to be used should be easily accessible, should be easy to store and transport and should be economical. If we are in city area, LPG should be used since it does not produce pollution, is easily available and is economical.
In rural area, gobar gas or biogas should be used. It is almost free, has high calorific value and is pollution free. It is also renewable source of energy.
2.What is Bio-energy?
Ans. Bio-energy is the energy generated by biomass. Energy may be in form of fire, fuel oil, biogas, animal dung alcohol, charcoal or even human excreta. Fuels are derived from bio-mass. It is an indirect source of solar energy and is renewable source of energy.
3.Hydrogen gas has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG. Why or why not?
Ans. The by-product of hydrogen when used as a fuel and burnt is water while that of CNG are water and carbon dioxide gas. Water is an absolutely harmless by-product, however carbon dioxide in the environment causes green house effect leading to global warming. Hence, hydrogen can be called a cleaner fuel than CNG.
4.“Only a small part of the solar energy that strikes the upper regions of atmosphere, reaches the surface of the earth”. Discuss?
Ans. When the solar energy falls in the top surface of the atmosphere then some solar energy is reflected back into the space by the atmosphere, and the atmosphere also absorbs a lot of solar energy, for example most of the ultra violet rays are absorbed by the ozone layer. So the solar energy which reaches on the earth’s atmosphere is mainly in the form of heat rays (infrared rays) and visible light, which is a small part of the solar energy.
5.What is geo-thermal energy? What are its limitations?
Ans. Geo-thermal energy is the heat of the earth and is the naturally occurring thermal energy found within rock formations and the fluids held within those formations. Geo-thermal energy is on of those few sources that do not come directly or indirectly from the solar energy.
Limitations
i)Goe-thermal hot spots are scattered and usually some distance away from the areas that need energy.
ii)The overall power production has lower efficiency (about 15%) as compared to that of fossil fuels (35% to 40%)
iii)Though as a whole geothermal energy is inexhaustible, a single bore has a limited life span of about 10 yrs.
iv)Noise pollution is caused by drilling operations at geo-thermal sites.
LAQ (5marks)
1.What are environment consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Ans. The demand of energy consumption is increasing day to day. Exploiting any source energy may disturb the environment in one-way or other. For example getting energy from fossil fuel may cause lot of pollution in air. Getting energy from nuclear fission may create problem of disposal of nuclear waste.
Steps for reducing energy consumption should be such that we get maximum energy from least fuel. For this:
i.Under the given situation technology utilized should be the best possible. For example. Using smokeless chulhas should be preferred to traditional chulhas.
ii.Energy should be extracted by most economic method under the given situation. Where as energy extraction by solar cells may be useless in big towns due to cost factor, it may be indispensable for artificial satellites.
iii.Wastage of energy should be strictly avoided. Energy saved is equal to energy produced.
iv.Sources of energy should be such that it causes least damage to environment.
15.Our environment
VSAQ (1 marks)
1.Would you eat animals or plants to get more calories of heat?
Ans. We should eat plants to get more calories of heat.
2.What will happen if we kill all the organisms in one tropic level?
Ans.If we kill all the organisms in one tropic level, unbalances are created in the food chain.
3.Write an aquatic food chain?
Ans. Phytoplankton ton zooplanktonfishseal
4.Why ozone layer is called radiation belt?
Ans. Because it checks the entry of high energy UV-radiations of sunlight in the earth’s atmosphere.
5.What is detritus?
Ans. Dead organic matter.
6.Explain why the practice of serving tea in Kulhads (disposable cups made of clay) on trains has been discontinued.
Ans. Because the use of a lot of clay for making millions of Kulhads daily lead to the loss of fertile top soil in the fields.
7.Write the full form of CFC. Give its one harmful effect.
Ans. The full form of CFC is Chloroflouro-carbons. Chloroflouro carbons are damaging the ozone layer in the upper atmosphere.
SAQ (2 marks)
1.How is the ozone formed?
Ans. Ozone is formed high up in atmosphere by the action of ultraviolet radiation on oxygen gas as follows.
O2 O + O
O2 + O O3 (ozone molecule)
Oxygen molecule.
2.State any two practices which can help in the protection of our environment.
Ans. i. Disposal of waste after its separation as biodegradable and non-biodegradable waste material
ii. Judicious use of unleaded petrol, alternate sources of energy. Engines of vehicles should also be properly tuned and serviced so that vehicles run efficiently.
3.Give two ways in which biodegradable substance would affect the environment.
Ans. i. Stink- Within a day or so waste biodegradable substances begin to stink and produce foul gases.
` ii. Pests and Pathogens- the decaying biodegradable substances become breeding places of many pests. Because of being waste in origin they often contain pathogens.
4.Which of the following are biodegradable and which non-biodegradable?
Glass bottle, Paper, Ball point pen refill, DDT, Wheat, Cake, Wood, Polythene bag, Cotton, Grass, Vegetable peels.
Ans. i. Biodegradable: Paper, Wheat, Cake, Wood, Jute bag, Cotton Cloth, Grass, Vegetable peels.
ii. Non- biodegradable: Glass bottle, Ballpoint pen refill, DDT, Polythene bag.
5.What is ‘Ten percent low’?
Ans. Ten percent low is an enunciation given by Lindeman (1942) that states that only 10% of energy contained in a lower tropic level, the remaining 90% being lost in transfer and respiration of the later.
SAQ (3 marks )
1.How is solar energy introduced into the ecosystem?
Ans. The green plants have a mechanism for trapping solar energy with the help of their green pigment called chlorophyll. The green plants after trapping the solar energy, convert it into chemical energy whish is stored as carbohydrates in the plants. Thus the initial point where energy from the environment enters into the living components of ecosystem (like plants and animals) is the process of preparation of food by green plants through photosynthesis.
2.How can you help in reducing the problems of waste disposal?
Ans. 1. Recycling of wastes.
2. Reduction at source.
3. Better management.
4. Vermi-composting.
` 5. Use of eco friendly products such as disposable paper cups in place of plastic cups,
Chapter 16
Management of Natural Resource
VASQ(1 marks)
1. Write utility of construction of dam and reservation.
Ans. Regular supply of water for irrigation, controlling floods and generating electricity.
2. Define biodiversity.
Ans. It refers to totality of genes, species and ecosystem of a region, eg -Forest.
3. Why was Ganga Action plan launched?
Ans. To restore quality of water in the Ganga. It was very poor due to pollution.
4. What are the three R’s to save environment?
Ans. Reduce, Recycle and Reuse.
5.The presence of which organism indicates the pollution index of water body?
Ans. The presence of coli form group of bacteria indicates the pollution index of water body.
6. Name the river with which Sardar Sarovar Dam is associated.
Ans. The river with which Sardar Sarovar Dam is associated is Narmada.
7. Give one criticism about large dam.
Ans. Large dams consume large amount of public money without the generation of proportionate benefits.
SAQ(2 marks)
1. Mention two ways in which water harvesting can be undertaken.
Ans. i. Capturing sum off water from roof-tops.
ii. Capturing sum off water from local catchments.
2. Why reuse better than recycling?
Ans. Reuse is better than recycling because the process of recycling uses some energy. In the reuse strategy we simply use things again and again.
3. What would be advantages of exploring resources with short terms aims?
Ans. Exploring resources with short-term aims provide immediate advantage that meet current basic human need.
4. How can you as an individual contribute or make a difference to management of (i) water resources and (ii) Coal and petroleum?
Ans.(i) Running water will not be used for brushing teeth or taking bath. Water will be taken in a mug and bucket for these purpose to prevent wastage.
(ii) Switch off unnecessary lights and fans etc. and use bicycle to cover short distances instead of a scooter or car.
5. Write down any two consequences of deforestation.
Ans. i. Change in climate and global warming
ii. Soil erosion and floods.
6. Name any two endangered plant and animal species.
Ans. Endangered plant species- Pitcher Plant and Snow orchid.
Endangered animal species- Indian wild Ass and Great Indian Rhinoceros
SAQ ( 3marks)
1. Can you suggest some changes in yours school whish would make it environment friendly?
Ans. i. School busses should be run on CNG instead of diesel.
ii. Trees should be planted along the school boundary.
iii. The fallen leaves of trees should be collected and made into compost. This compost can be used in school garden.
2. What are the causes of pollution of Ganga river?
Ans. 1. Dumping of garbage and untreated swage from all the towns and cities on the banks of the ricer.
ii. Bathing by millions of people, washing clothes, animals and vehicles in the river water.
iii. Immersion of ashes or even dead bodies in the performance of rituals.
iv. Releasing chemical effluents from industries directly into the river water.
3. Find out the traditional system of water-harvesting/ management.
Ans. Traditional system of water harvesting/ management.
i. Diversion of water flowing in streams into man made channels to cater to the demand of the people
ii. Collection of water in ponds.
iii. Contraction of dams.
4. Why is dependence of man or nature greater than that of any other organism?
Ans. Man’s dependence on nature is greater than that of any other organism because he:
i.Has developed curiosity for more comforts and security.
ii.Consumes large amount of material and energy.
iii.Has developed a new bond of socio-economic environment which consists of things developed by man through his tools and techniques.
5.What is Chipko Andolan?
Ans. This movement was launched by people of Reni in Garhwal. It was spearheaded by Sundar Lal Bahuguna. The Chipko Andolan (Hug the trees Movement) was the result of a grass- root level effort to end the alienation of people from their forests. The movement originated from an incident in a remote village called Reni in Garhwal during the early 1970’s The women of the village reached the forest and clasped the tree trunks to trees and felling it. Thus thwarted the constructor had to withdraw.
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