Biology Today 2013-02

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A miracle in medical research

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rofessor Robert Maclaren and his group in the University of Oxford have developed a method of giving sight to the born blind. The research was performed on mice that had no photoreceptions in their retinas. The result is they cannot distinguish between night and day or light and darkness. The scientists injected light sensing cells into the eye and two weeks after the injection, a retina has been formed. This was curing a case of a complete lack of retina. Previous studies had successfully treated partially degenerated retinas. After the development of the new retina, not only the mice showed constriction of pupils when irradiated with light, but also studies on their brain showed that the visual information was being processed by the brain.

According to Pete Coffee from the Institute of Ophthalmology at the University of London, the finding were important as the studies looked at most clinically relevant and severe cases of blindness however, he said this and similar studies needed to show how good the recovered vision was as brain scans and tests of light sensitivity were not enough.

Loss of sight due to various injuries and blindness since birth or after suffering a serious disease like small-pox all can be corrected by this method. Replacing heart valves, insertion of pacemakers, grafting in liver and treating rheumatism and weakness of bones by modern techniques are being practiced in India in many of our hospitals. Every single technique or discovery in any part of the world is also an asset to every country in the world. Whether is research on radioactive materials or in information technology, they are the collective wealth of the world. Any discovery in any part of the world will be available in every city, thanks to the Informatic Explosion.

Research and Publication- are the right hand and the left hand of progress.

Anil Ahlawat Editor Subscribe online at www.mtg.in

Owned, Printed and Published by Mahabir Singh from 406, Taj Apartment, New Delhi - 29 and printed by Personal Graphics and Advertisers (P) Ltd., Okhla Industrial Area, Phase-II, New Delhi. Readers are adviced to make appropriate thorough enquiries before acting upon any advertisements published in this magazine. Focus/Infocus features are marketing incentives MTG does not vouch or subscribe to the claims and representations made by advertisers. All disputes are subject to Delhi jurisdiction only. Editor : Anil Ahlawat

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Q1. Why melatonin is referred to as “sleep hormone”?

Refer : Assertion and Reason – Endocrine system.

Q2. How restriction modification system in bacteria functions as a part of defense mechanism against bacteriophages infection?

Refer : NEET Special – Biotechnology.

Q3. Why gout sufferers should avoid consuming meat, particularly liver, kidney, brain, thymus gland and other glands?

Refer : High Yield Facts – Common Human Diseases-II.

Q4. What are two forms of diabetes mellitus?

Refer : High Yield Facts – Common Human Diseases-II.

Q5. Climax community has maximum diversity and niche specialization. Justify.

Refer : High Yield Facts – Ecological Succession.

Q6. Give an example of induced succession.

Refer : High Yield Facts – Ecological Succession.

Q7. Why men have higher hematocrit than women? explain.

Refer : PMT Essential – Blood and Hemostasis.

Q8. What is the rate-limiting factor in blood coagulation cascade?

Refer : PMT Essential – Blood and Hemostasis.

Q9. Which evolutionary force is believed to be the driving force behind sympatric speciation?

Refer : CBSE Board – Sample Paper.

Q10. During expiration, how is the pressure gradient formed between the lungs and the atmosphere?

Refer : Concept Map - Breathing and Respiration.

Note : ‘xplore’ also serves as Quiz which is open for the readers to solve.

You can send in your answers to us either through e-mail or by post and, reader with more correct answers will be rewarded with exciting prize.

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Dear Readers,

The purpose of this xplore & Win is to develop curiosity in you about the biological concepts and to give you an opportunity to learn in investigative manner.

This will connect the biological concepts with their applications in real world and will put interesting-to-search queries.

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GENERAL INSTRUCTIONS

(i) All questions are compulsory.

(ii) The question paper consists of four sections A, B, C and D. Section-A contains 8 questions of 1 mark each, Section B is of 10 questions of 2 marks each, Section C is of 9 questions of 3 marks each whereas Section D is of 3 questions of 5 marks each.

(iii) There is no overall choice. However, an internal choice has been provided in one question of 2 marks, one question of 3 marks and all the three questions of 5 marks weightage. A student has to attempt only one of the alternatives in such questions.

(iv) Wherever necessary, the diagrams drawn should be neat and properly labelled.

SECTION - A

1. Mention any four asexual reproductive structures that is found among different groups of organisms.

2. Compatibility reaction is determined by special proteins X and Y, X being present over zona pellucida and Y is over sperm surface. What are X and Y?

3. In 1928, after a series of experiments with Streptococcus pneumoniae, Frederick Griffith concluded that some ‘transforming principle’, transferred from the heat-killed S-strain had enabled the R-strain to synthesize. A smooth polysaccaride coat and to become virulent. What is this ‘transforming principle’?

4. Compare male heterogamety and female heterogamety. 5. Which lymphoid tissue constitutes about 50 per cent of the

lymphoid tissue in human body?

6. Give an example of crop which is produced by mutation breeding method.

7. Which novel strategy is being adopted to prevent nematode infestation in dicot plants?

8. Out of every 10 animals on Earth, 7 are ______. (a) mammals (b) crustaceans (c) molluscs (d) insects.

SECTION - B

9. Evolution is a stochastic process based on chance events in nature and chance mutation in the organisms. Justify.

10. Differentiate between flowers of bringal and beans. 11. Study the given graph and answer the questions that

follows.

(i) Name the hormones X, Y and Z.

(ii) The presence of which of these hormones (X, Y or Z) in urine helps in detecting pregnancy?

12. List any four objectives that you would recommend for biofortification.

13. Trace the development of microsporocyte in the anther to a mature pollen grain.

14. Why organs for transplantation cannot be taken from just anybody?

15. Give the scientific names for the following:

(i) The joining of genes, set of genes or parts of genes, into new combinations, either biologically or through laboratory manipulation.

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_{FEBRUARY ’13} ₇ (ii) An independent, stable, self replicating piece of DNA

in a bacterial cell that is not a part of the normal cell genome and that never becomes integrated into the host chromosome.

(iii) A small segment of DNA that binds to a complementary strand of DNA.

(iv) A technique used for introducing a solution of DNA into a cell using a fine microcapillary pipette.

16. Represent diagrammatically the formation and joining of sticky ends of DNA.

17. Refer the given figure to answer the questions that follow.

(i) What is X?

(ii) Why is X important for molecular geneticists?

18. State the differences between intraspecific and interspecific competition.

OR

Why secondary succession is faster than primary succession?

SECTION - C

19. Which type of natural selection is believed to be the driving force behind the sympatric speciation? Explain.

20. What is gametogenesis? Name its two types and give differences between them.

21. (i) In which of these seeds, endosperm is persistent? Wheat, Rice, Barley, Pea, Bean, Palm.

(ii) Write down the fate of endosperm.

22. In a large population, only a person in 10,000 is albino. What will be the frequency of carriers of albinism in the population?

23. Refer the given figure of lac operon and answer the questions that follow.

(i) When the i-gene is constitutively expressed, then substance labelled ‘X’ will be inducer or inhibitor? Explain.

(ii) The z gene has undergone nonsense mutation. What would be the possible consequences of this?

24. Fill in the blanks in the given table.

Disease Pathogen Vector Symptoms

— Entamoeba

histolytica — Abdominal pain, _{diarrhoea, blood} in faeces. Malaria Plasmodium Anopheles — African

sleeping sickness

— Glossina

palpalis Recurrent fever, anaemia, patient falls asleep.

Kala-azar or Dumdum fever

— — High fever, spleen

enlargement, anaemia, darkening of skin. OR

(i) Mention the property that enables the explants to regenerate into a new plant.

(ii) A banana herb is virus-infected. Describe the method that will help in obtaining healthy banana plants from this diseased plant.

25. The cloning vector pBR322 has two antibiotic resistance genes: ampicillin and tetracycline. This is because one antibiotic resistance gene helps in selecting the transformants, whereas the other antibiotic resistance gene helps in selection of recombinants. Explain.

26. In winter, storms have brought nutrient-rich water into a lake. Based on the data on the population of unicellular algae in the lake throughout the year, the given graph is plotted.

(i) What term is given to the condition occurring in summer months?

(ii) Suggest possible conditions that you would observer between May to September.

27. Describe in detail the species area relationship as given by Alexander von Humboldt.

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SECTION - D

28. A dihybrid heterozygous round yellow seeded garden pea (Pisum sativum) offspring was crossed with a double recessive parent :

(i) What type of the cross is this ?

(ii) Work out the genotype and phenotype of the progeny. (iii) What principle of Mendel is illustrated through the result

of this cross ?

OR

In what way did Lederberg’s experiment provide a clear support to Darwinian view point of selection?.

29. Discuss the causes and effects of global warming. What measures need to be taken to control global warming?

OR

(i) What is photochemical smog composed of? How does this affect the plants?

(ii) Mention the consequences of deforestation.

*30. A farmer is struggling to grow vegetables and crops in his field. He has applied many available fertilizers to improve the fertility of the field, but this has shown opposite effect, the field has become barren due to overuse of fertilizers. (i) Do you think, the farmer must know the webs of interaction

between the myriad of organisms that constitute the flora and fauna of the field?

(ii) What changes in agricultural practices would you suggest him?

SOLUTIONS

1. Zoospores (Chlamydomonas), conidia (Penicillium), buds (Hydra) and gemmules (sponge).

2. X - Fertilizin; Y - Antifertilizin. 3. DNA is the transforming principle.

4. Comparison of male heterogamety and female heterogamety is as follows:

Male heterogamety Female

heterogamety 1. Male produces two different types

of gametes: (a) either with or without X-chromosome or (b) some gametes with X-chromosome and some with Y-chromosome.

Female produces two types of gametes either with Z or with W chromosome. 2. Examples, Drosophila, human, etc. Example, birds. 5. Mucosa associated lymphoid tissue (MALT). 6. Sharbati Sonora or Pusa Lerma.

7. RNA interference (RNAi). 8. (d) Insects.

9. Excess use of herbicides, pesticides, etc., has only resulted in selection of resistant varieties in a much lesser time scale. This is also true for microbes against which we employ antibiotics or drugs against eukaryotic organisms/ cell. Hence, resistant organisms/cells are appearing in a time scale of months or years and not centuries. These are examples of evolution by anthropogenic action. This also tells us that evolution is not a directed process in the sense of determinism. It is a stochastic process based on chance events in nature and chance mutation in the organisms. 10. Differences between flower of brinjal and beans are as

follows : Flower of brinjal (Chasmogamous flower) Flower of beans (Cleistogamous flower) 1. Open flowers with exposed

anthers and stigma and these flowers are similar to the flowers of other species.

Closed flowers in which anthers and stigma lie close to each other and anthers dehisce within flower buds.

2. Require pollinating agents.

Do not require pollinating agents.

3. These flowers favour cross pollination.

These flowers ensure self pollination.

11. (i) X - Human chorionic gonadotropin (HCG) Y - Oestrogen Z - Progesterone (ii) X - HCG.

12. Biofortification is the method of breeding crops with higher levels of vitamins and minerals or higher proteins and healthier fats in the view to improve public health. Four objectives of biofortification are to unprove (i) Protein content and quality

(ii) Oil content and quality (iii) Vitamin content

(iv) Micronutrient and mineral content.

13. In an anther, each cell of the sporogenous tissue is a potential pollen or microspore mother cell (PMC). Each PMC divides by meiosis to form a microspore tetrad. This process is called microsporogenesis. As the anthers mature and dehydrate, the microspores dissociate from each other and develop into pollen grains. The hard outer layer called the exine is made up of sporopollenin. The inner wall of the pollen grain is called the intine. When the pollen grain is mature it contains two cells, the vegetative cells and generative cell.

* Value based question

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_{FEBRUARY ’13} ₉ 14. Success for transplantation depends on the degree of

compatibility between donor and graft. Grafts from just any source - an animal, another primate, or any human beings cannot be made since the grafts would be rejected sooner or later. Tissue matching, blood group matching are essential before undertaking any graft/transplant and even after this the patient has to take immuno-suppresants all his/her life. The body is able to differentiate ‘self’ and ‘nonself’ and the cell-mediated immune response is responsible for the graft rejection.

The success of tissue and organ transplants depends on the donor’s and recipient’s human leucocyte antigens (HLA) encoded by the HLA genes. These proteins are alloantigens; i.e, they differ among members of the same species. If the HLA proteins on the donor’s cells differ from those on the recipient’s cells, an immune response occurs in the recipient. The genes for the HLA proteins are clustered in the major histocompatibility complex (MHC), located on the short arm of chromosome 6.

15. (i) Recombination (ii) Plasmid

(iii) Primer (iv) Microinjection.

16. Restriction enzyme Eco RI cuts both DNA strands at the same site i.e., between bases G and A in GAATC sequence present in the DNA.

17. (i) X - Ti plasmid.

(ii) Agrobacterium tumifaciens is a soil-inhabiting bacterium that may invade growing plants at the junction of root and stem, where it can cause a cancerous growth known as a crown gall. The bacterium, which infects dicotyledonous plants only, contains plasmid (known as a Ti plasmid) that carries the genes for tumour formation. When the bacterium invades the host cells the Ti plasmid enters the host nuclei. Part of the Ti plasmid become inserted into the chromosome, introducing genes for their growth of the bacterium.

For using Ti plasmid as a vector, researchers have eliminated its tumor causing properties while keeping its ability to transfer DNA into plant cells. This bacterium is called natural genetic engineer because genes carried by Ti plasmid produce effect in several parts of the plant.

18. Differences between intraspecific and inter-specific competition are as follows:

Intraspecific

competition Interspecific competition (i) It is competition among

individuals of the same species.

The competition is amongst the members of different species.

(ii) The competition is for all the requirements.

The competition is for one or a few requirements. (iii) The competing

individuals have similar type of adaptation.

The competing individuals have different types of adaptations.

(iv) It is more severe due to similar needs and adaptations.

It is less severe as the similar needs are a few and the adaptations are different. OR

Ecological succession is of two types – primary and secondary succession. Primary succession is a biotic succession which occurs on a previously bare or unoccupied area, e.g., new exposed rock area, sand dunes, igneous rocks, deltas, newly created pond or reservoir. The establishment of a new biotic community is generally slow. Before a biotic community of diverse organisms can become established, there must be soil. Depending mostly on the climate, it takes natural processes several hundred to several thousand years to produce fertile soil on bare rock.

Secondary succession is a biotic succession that occurs in an area from which a community has been removed and

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where nutrients and conditions for existence are present, e.g., cut over forest, abandoned crop land, ploughed fields and lands that have been flooded. Since some soil or sediment is present, secondary succession is faster than primary succession.

19. Disruptive natural selection, also called diversifying selection, describes changes in population genetics in which extreme values for a trait are favored over intermediate values. In this case, the variance of the trait increases and the population is divided into the distinct groups. This evolutionary process is to be one of the main driving forces behind sympatric speciation. For example, in a forest, a moth population have homozygotes for black or white and heterozygotes are grey. The disruptive selection would favor black and white favor moths over grey moths. This might be because in the forest trees have either light bark or really dark bark. In such environment, it would be less advantageous to have the medium grey colour than the two extreme colours because grey would stand out on either type of tree and predators would have an easy target,

Sympatric speciation occurs when a single population begins to diverge into two without any sort of geographical barrier to separate them. Using the previous example of moths, the black moths would tend to mate with black ones and white moths would mate with white ones because they would produce offsprings that are better adapted to the environment. Eventually, the black and white moths would, split into two reproductively isolated species. In this manner, disruptive natural selection can be the driving force behind sympatric speciation.

20. Gametogenesis is the process by which male and female sex cells or gametes i.e. sperms and ova are formed respectively

in the male and female gonads. Gametogenesis is of two types: spermatogenesis (formation of sperms) and oogenesis (formation of ova).

Differences between spermatogenesis and oogenesis are given in the following table :

Spermatogenesis Oogenesis

(i) It is generally completed in the testes and thus mature sperms are released from the testes.

It is often completed in the female reproductive tract or in many animals in water because oocytes are released from the ovaries. (ii) A primary

spermatocyte divides to form two secondary spermatocytes.

A primary oocyte divides to form one secondary oocyte and one polar body. (iii) A secondary

spermatocyte divides to form two spermatids.

A secondary oocyte divides to form one ootid and one polar body.

(iv) A spermatogonium forms four spermatozoa.

An oogonium forms only one ovum.

21. (i) Endosperm is persistent in wheat, rice, barely and palm.

(ii) As the endosperm develops, it fills up the nucellus. In many seeds no endosperm is seen at maturity although it is always formed at the initial stage of embryo development. During the process of the development of the embryo, the food stored up in the endosperm is continuously drawn up by the developing embryo and thus completely exhausted. Such seeds are known as exalbuminous or non-endospermic. In other cases, where the endosperm grows vigorously and is not completely exhausted by the developing embryo, the seed is known as albuminous or endospermic. The common examples are : exalbuminous – gram, pea, bean, tamarind, orchid, sunflower, etc.; albuminous – castor, poppy, rice, wheat, barley, coconut, palm, grasses etc.

22. Hardy-Weinberg principle states that in a large, randomly interbreeding population, the allelic frequencies in a population remain stable and is constant from generation to generation. This is called genetic equilibrium where gene pool is constant and sum total of all the frequencies is 1. Hardy-Weinberg represented this using an algebraic equations which as following:

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_{FEBRUARY ’13} ₁₁ p2_{+ 2pq+ q}2_{= 1}

also, p + q = 1

where, p is frequency of dominant allele and q is frequency of recessive allele. Hence, p2_{is the frequency of individuals}

in the population that are homozygotic dominant i.e., AA and q2_{is the frequency of individuals in the population that}

are homozygotic recessive i.e., aa. 2pq represents frequency of individuals in the population that are heterozygotic or carriers.

Now, we are given data about individuals showing albinism. Albinism is due to autosomal recessive disorder.

Therefore, number of individuals with albinism is: q2_{= 1/10000 or 0.0001}

\ q = 0 0001 0 01. = . Now, p + q = 1 \ p = 0.99

So, the frequency of carriers of albinism in the population i.e., 2pq, is 2 pq = 2 × 0.99 × 0.01 = 0.0198  0.02 2 2 100 1 50 pq= or /

Thus, in the given population, 1 person in every 50 individuals would be carrier of albinism.

23. (i) The i gene is regulatory gene of lac operon. The i gene codes for the repressor of the lac operon. Since i gene is constitutively expressed, i.e., repressor protein encoded is always available to bind with operator region of the operon and to prevent RNA polymerase from transcribing. Thus, in the presence of an inducer, such as lactose or allolactose, the repressor is inactivated by their interaction. The ‘X’ in the given figure is, thus, inducer. Regulation of lac operon is thereby, positive regulation.

(ii) Nonsense mutation is a point mutation in which replacement of a single base nucleotide with another nucleotide converts an amino acid codon into a termination codon. This can truncate the encoded protein and make it nonfunctional. The z gene codes for beta-galactosidase, which is primarily responsible for the hydrolysis of the disaccharide, lactose into its monomeric units, galactose and glucose. As a consequence, E.coli would not be able to catalyse the hydrolysis of a lactose and thus bacteria would not be able to use it as a source of energy, leading to perishment of the bacteria.

24.

Disease Pathogen Vector Symptoms

Amoebiasis Entamoeba

histolytica _{nated food}Contami- Abdominal pain, _{diarrhoea, blood} in faeces. Malaria Plasmodium Anopheles Fever, acute

chillness, sweating, nausea African sleeping sickness Trypanosoma Glossina

palpalis Recurrent fever, anaemia, patient falls asleep. Kala-azar or Dumdum fever Leishmania donovani Phleboto-mus High fever, spleen enlargement, anaemia, darkening of skin. OR

(i) The property to generate a whole plant from any cell/explant is called totipotency.

(ii) In case of asexually reproducing crops like banana, virus infections spread rapidly. This is because the vegetative propagules from virus-infected plants contain virus particles. But the shoot apical meristems and some young tissues surrounding them are often free from viruses. Meristem culture, therefore, is often useful in recovering virus-free plants from virus-infected plants or clones.

The explants commonly used in meristem culture are shoot tips and nodal segments. These explants are cultured on a medium containing a cytokinin (generally BAP). The plantlets thus obtained are subjected to hardening and, ultimately, established in the field.

25. E.coli cloning vector pBR322 have two antibiotic resistance genes for ampicillin and tetracycline. The ligation of alien DNA is carried out at a restriction site present in one of the two antibiotic resistance genes. For example, you can ligate a foreign DNA at the Bam H I site of tetracycline resistance gene in the vector pBR322. The recombinant plasmids will lose tetracycline resistance due to insertion of foreign DNA. So, when a recombinant DNA bearing gene for resistance to an antibiotic (e.g., ampicillin) is transferred into E.coli cells, the host cells become transformed into ampicillin-resistant cells. If we spread the transformed cells on agar plates containing ampicillin, only transformants will grow, untransformed recipient cells will die. Since, due to ampicillin

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resistance gene, one is able to select a transformed cell in the presence of ampicillin. The ampicillin resistance gene in this case is called a selectable marker.

Similarly, recombinants can be selected out from non-recombinants, as the recombinants will grow in ampicillin containing medium but not on that containing tetracycline, but, non-recombinants will grow on the medium containing both the antibiotics. In this manner, one antibiotic resistance gene helps in selecting the transformants, whereas the other antibiotic resistance gene gets ‘inactivated due to insertion’ of alien DNA, and helps in selection of recombinants. 26. (i) Algal bloom.

(ii) The excess growth of planktonic algae causes algal bloom. This imparts a distinct colouration to the water bodies. It causes deterioration of the water quality and fish mortality. It may also support excessive growth of floating plants. Water hyacinth (Eichhornia crassipes) is one such plant that may choke lake. Algal bloom and floating plants together would cut off light from submerged plants. The latter would die. There would be a drastic decrease in oxygen replenishment inside water. It may cause organic loading of water. Some bloom forming algae are extremely toxic to human beings and animals.

27. Species area relationship of biodiversity was given by Alexander von Humboldt while he was exploring the South American jungles. He observed that within a region species richness increased with increasing explored area, but only up to a limit. The relation between species richness and area for a wide variety of taxa turns out be a rectangular hyperbola.

On a logarithmic scale, the relationship is a straight line described by the equation

log S = log C + Z log A where

S = Species richness A = Area

Z = Slope of the line (regression coefficient) C = Y-intercept

The value of Z lies in the range of 0.1 to 0.2, regardless of the taxonomic group or the region. But, if the species

area relationships among very large areas like the entire continents is analyzed, the slope of the line is much steeper (Z values in the range of 0.6 to 1.2).

28. (i) This is a test cross. (ii)

(iii) Principle of independent assortment is illustrated through the result of this cross.

OR

Joshua Lederberg and Esher Lederberg demonstrated the genetic basis of adaptation in bacteria with the help of an experiment called Lederberg’s replica plating experiment. They inoculated a dilute suspension of bacteria cells on a semisolid agar plate. The agar plate bearing colonies was used as a ‘master plate’ to obtain its replicas. The replica proliferated but when they attempted to make replicas using plates containing an antibiotic penicillin, most of the colonies failed to grow except a few which were resistant to penicillin. This shows that in the master plate were present a few colonies which were antibiotic resistant before the application of the penicillin. This resistance would have developed in them by chance mutation. This shows that adaptation has genetic basis. The experiment support Darwinism and its view on natural selection. It clearly illustrates that a change in the environment, in this case the introduction of penicillin, gave selective advantage to the penicillin resistant bacteria over the penicillin sensitive bacteria. The penicillin resistant bacteria though already present had no advantage and so were not evident. 29. Greenhouse effect is the progressive, gradual warming

of the earth’s atmosphere caused by the insulating effect of carbon dioxide and other green-house gases that have proportionately increased in the atmosphere. The greenhouse effect disturbs the way the Earth’s climate maintains the balance between incoming and outgoing energy by allowing short-wave radiation from the sun to penetrate through to warm the Earth, but preventing the resulting long-wave infrared radiation from escaping back into the atmosphere. There is concern that increasing concentration of greenhouse gases, including carbon dioxide, methane, and man made chlorofluorocarbons, may enhance the greenhouse effect and cause global warming.

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_{FEBRUARY ’13} ₁₃ Effects of global warming are :

Warming of atmosphere will significantly increase its –

moisture carrying capacity. While the trophosphere warms up, the stratosphere will cool down. This would cause extensive changes in precipitation patterns due to changed pattern of air-mass movements. Besides, the frequency of droughts, floods, etc., is estimated to increase substantially. The climate change will increase threats to human health, predominantly in tropical and subtropical countries, due to change in ranges of disease vectors, water-borne pathogens, etc.

The global warming may contribute to sea level rise –

due to the thermal expansion of oceans as it warms, and melting of glaciers and Greenland ice sheets. A rise of even half a meter in sea level would profoundly affect human population, one-third of which lives within 60 km of a coastline. Numerous low-lying islands may be submerged. Inundation of coastal salt marshes and estuaries may deprive of many important birds and fishes, their breeding grounds, forcing their extinction.

Strategies to deal with global warming :

Complete replacement of chlorofluorocarbon with –

substitutes that have little effect on ozone and global warming.

Increasing vegetation cover of forests for photosynthetic –

utilization of CO₂.

Reduction in use of nitrogen fertilizers and instead –

relying more on nitrogen fixation.

Limiting use of fossil fuels by developing alternate –

sources of energy, eg., solar energy, wind energy. Increasing use of alternative, renewable, nonpolluting –

sources of energy like solar energy, wind energy, hydropower etc.

Preponing the use of hydrogen fuel. –

OR

(i) Photochemical smog is composed of secondary air pollutants. It is formed by interaction of hydrocarbons with nitrogen oxides. The products are ozone, peroxyacyl nitrate (PAN), aldehydes and phenols. Photochemical smog leads to necrosis and chlorosis in plants.

(ii) The consequences of deforestation are as follows : Change in climate : Deforestation results in reduced –

rainfall, increased drought, hotter summers and colder winters.

Soil erosion : Soil is exposed to insolation, dries up and –

gets eroded by wind and water. It is estimated that 6000 million tonnes of top soil is lost annually in India due to water erosion in the absence of forest cover.

Drought : There is very little water in rivers during day –

season causing drought.

Loss of biodiversity and germplasm. –

Global warming : Deforestation increases atmospheric –

CO₂ content by releasing carbon stored in organic matter and reduced primary productivity.

30. (i) Yes. Nowadays, the ‘conventional’ farming practices often use chemical methods such as use of insecticides, pesticides, etc. to control plant diseases and pests and to increase yield. However, these chemicals are toxic and extremely harmful, to human beings and animals alike, and have been polluting our environment (soil, ground water), fruits, vegetables and crop plants. Our soil is also polluted through our use of weedicides to remove weeds.

These conventional farming practices of using chemical methods, result in killing both useful and harmful life forms indiscriminately. Therefore, it is essential to develop an understanding towards a holistic approach of farming which considers the webs of interaction between myriad of organisms of the field because the eradication of the creatures that are often described as pests is not only possible, but also undesirable, for without them the beneficial predatory and parasitic insects which depend upon them as food or hosts would not be able to survive.

the holistic approach would not only help in regaining back the fertility of the farmer’s field but also would keep pests, etc., under manageable levels without the use of chemicals.

(ii) I would suggest him to switch to organic farming. Due to the overuse of chemical fertilisers, the field has lost natural nutrients as well as beneficial interaction between flora and fauna (insects). Organic farming is the farming practise which does not use artificial fertilisers and pesticides instead it uses biopesticides and biofertilisers. Biofertilisers are micro-organisms which bring about nutrient enrichment of soil by enhancing the availability of nutrients like nitrogen and phosphorus to crops. The main biofertilisers are bacteria, mycorrhizal fungi and cyanobacteria.

Bacteria and cyanobacteria have the property of nitrogen fixation while mycorrhizal fungi preferentially absorb phosphorus from soil and passes it to the plant with which they are associated. Plants having such associations show other benefits also, such as resistance to root-borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue green algae also add organic matter to the soil and increase its fertility.

nn

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1. Assertion (A) : In respiration, energy of oxidation-reduction is utilized for the phosphorylation reaction (i.e., ATP synthesis) and thus the process is called oxidative phosphorylation.

Reason (R) : In photosynthesis, light energy is utilized for ATP synthesis, and thus the process is called photophosphorylation.

2. Assertion (A) : Glycolysis occurs in mitochondrial matrix.

Reason (R) : Krebs’ cycle occurs on the cristae of mitochondria.

3. Assertion (A) : Electron Transport Chain (ETC) is a set of seven electron carriers present in a specific sequence along inner mitochondrial membrane.

Reason (R) : H2O acts as the final hydrogen acceptor

during ETS.

4. Assertion (A) : Clostridium tetani is an obligate anaerobe.

Reason (R) : It cannot live in high O2 concentration.

5. Assertion (A) :The process of fermentation accounts for only a partial breakdown of glucose.

Reason (R) :In aerobic respiration, complete breakdown of glucose to CO2 and H2O takes place.

6. Assertion (A) :End products of alcoholic fermentation are ethanol and CO2.

Reason (R) : Pyruvic acid is first decarboxylated to acetaldehyde which in turn is converted into ethanol.

7. Assertion (A) : When fats are used as respiratory substrates, value of RQ is less than one.

Reason (R) :During oxidation of fatty acids, O2 absorption

is more and CO2 liberation is less.

8. Assertion (A) : Glycolysis occurs in cytoplasm and produces 2ATP and 2NADH2.

Reason (R) :Glycolysis occurs both in aerobic as well as anaerobic respiration.

9. Assertion (A) : Respiratory pathway is considered as an amphibolic pathway.

Reason (R) : Respiratory pathway is involved in both anabolic and catabolic processes.

10. Assertion (A) :During aerobic respiration, pyruvic acid formed as a result of glycolysis, undergoes phosphorylation reaction to form acetyl CoA.

Reason (R) : Phosphorylation reaction is catalyzed by enzyme dehydrogenase.

In each of the following questions, a statement of Assertion (A) is given and a corresponding statement of Reason (R) is given just below it. Of the statements, mark the correct answer as :

(a) if both A and R are true and R is the correct explanation of A (b) if both A and R are true but R is not the correct explanation of A

(c) if A is true but R is false (d) if both A and R are false.

Plant Respiration

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_{FEBRUARY ’13} ₁₅

ANSWERS

1. (b)

Explanation of ‘A’ & ‘R’ :– The process of synthesis of ATP from ADP and Pi is called as phosphorylation. During respiration, energy of oxidation–reduction is utilized for the phosphorylation reaction and thus the process is called oxidative phosphorylation. It occurs in the inner mitochondrial membrane.

During photosynthesis, light energy is utilized for the phosphorylation reaction and thus the process is referred to as photophosphorylation. It takes place in thylakoid membranes.

Result : Hence, it is proved that both ‘A’ and ‘R’ are true but as ‘R’ is not the correct explanation of ‘A’, so the answer is option (b).

2. (d)

Explanation of ‘A’ & ‘R’:– Glycolysis is the stepwise oxidation of glucose to pyruvic acid without the use of oxygen. It occurs in the cytoplasm of cells, not in the mitochondria. Krebs’ cycle, also known as TCA cycle (Tricarboxylic acid cycle) or citric acid cycle, takes place in the matrix of mitochondria. It occurs during aerobic respiration only.

Result : Hence, it is proved that both ‘A’ and ‘R’ are false, so the answer is option (d).

3. (c)

Explanation of ‘A’ & ‘R’:– The various components of electron transport system include-cytochrome b, 2 types of cytochrome c, ubiquinone, flavoprotein (FMN or FAD), iron-sulphur protein (Fe–S) and enzyme cytochrome oxidase which is intimately associated with cytochrome a and a3. These components are

arranged in four kinds of complexes – Complex I (NADH dehydrogenase complex), Complex II (Succinate dehydrogenase complex), Complex III (Cytochrome bc1 complex) and Complex IV (cytochrome c oxidase

complex). There is a fifth complex, ATP synthase complex, which is involved in ATP synthesis. These complexes are arranged in a definite sequence in the inner mitochondrial membrane.

Final step of ETSis called as terminal oxidation, catalyzed by enzyme cytochrome oxidase, during which electrons from cytochrome c are transferred via. cyt a and cyt a3 (cytochrome oxidase complex) to oxygen. Thus O2

acts as final e–_{acceptor (or final hydrogen acceptor)}

during ETS.

Result : Hence, it is proved that ‘A’ is true and ‘R’ is false, so the answer is option (c).

4. (a)

Explanation of ‘A’ & ‘R’:– The bacteria belonging to the category of obligate anaerobes, respire only anaerobically. They generally get killed under aerobic conditions e.g., Clostridium tetani, C. botulinum.

Result : Hence, it is proved that both ‘A’ and ‘R’ are true and as ‘R’ is the correct explanation of ‘A’, so the answer is option (a).

5. (b)

Explanation of ‘A’ &‘R’:– Anaerobic respiration, also called fermentation, involves the partial breakdown of glucose in the absence of oxygen. The end products of fermentation may be ethanol and CO2 (alcoholic fermentation) or lactic

acid (lactic acid fermentation). It is a low energy yielding process and one of the end products is always organic. Aerobic respiration is the complete oxidation of glucose into CO2 and H2O in the presence of oxygen.

C6H12O6 + 6O2 → 6CO2 + 6H2O + 686 Kcal.

It is a high energy yielding process and occurs in most of the higher plants and animals.

6. (a)

Explanation of ‘A’ & ‘R’ :– Alcoholic fermentation involves two steps:

(i) Decarboxylation of pyruvic acid to acetaldehyde in the presence of enzyme pyruvate decarboxylase, co-enzyme thiamine pyrophosphate (TPP) and Zn2+_{as cofactor.}

(ii) Acetaldehyde accepts 2H atoms from NADH2, in the

presence of enzyme ethanol dehydrogenase and changes into ethanol.

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_{FEBRUARY ’13} 7. (a)

Explanation of ‘A’ & ‘R’ :– Consider an equation of oxidation of a fatty acid, tripalmitin.

Thus, when fats are used as respiratory substrates, value of RQ comes out to be less than 1 because O2 absorption is more

and CO2 liberation is less during the oxidation process.

8. (b)

Explanation of ‘A’ & ‘R’ :– Glycolysis is also called as EMP pathway as its details were given by Embden, Meyerhof and Parnas, in 1930. Glycolysis is the stepwise oxidation of one molecule of glucose into two molecules of pyruvic acid. It occurs in cytoplasm. Glycolysis is called the common pathway as it occurs in both aerobic as well as anaerobic respiration. End products of glycolysis are 2 pyruvic acid molecules, 2ATP and 2NADH2.

9. (a)

Explanation of ‘A’ & ‘R’ :– The organic substances (i.e, carbohydrates, fats, proteins, etc) are broken down to release energy by the process of cellular respiration. This process

is considered as a catabolism or a catabolic pathway. However, the breakdown of respiratory substrates provides carbon skeleton for the synthesis of a large number of other essential plant products, such as polysaccharides, proteins, fats, nucleic acids, pigments, cytochromes, etc.

Fatty acids is broken down to acetyl CoA before entering the respiratory pathway when it is used as a substrate. But when the organism needs to synthesise fatty acids, acetyl CoA is withdrawn from the respiratory pathway for it. Hence, the respiratory pathway comes into the picture both during breakdown and synthesis of fatty acids.

The respiratory pathway, therefore acts both as catabolic as well as anabolic pathway. Thus, it is better to call it amphibolic pathway rather than as a catabolic pathway alone.

10. (d)

Explanation of ‘A’ & ‘R’ :– During aerobic respiration, the final product of glycolysis i.e., pyruvic acid is transported from the cytoplasm into mitochondria which undergoes oxidative decarboxylation. The reaction is catalyzed by an enzyme pyruvate dehydrogenase as follows:

Pyruvic acid + CoA + NAD+

Acetyl CoA + CO2 + NADH + H+.

Endocrine System

1. Assertion (A) : Progesterone prepares uterus for pregnancy, implantation and formation of placenta. Reason (R) : Hypersecretion of progesterone causes abortion.

2. Assertion (A) : Calcitriol accelerates bone formation.

Reason (R) : Calcitriol is the active form of cholecalciferol. It promotes absorption of Ca2+_{and phosphorus in the}

small intestine.

3. Assertion (A) : Epinephrine is called as emergency hormone.

Reason (R) : Stimulation of the sympathetic nerves to adrenal medulla causes release of large quantities of adrenaline and noradrenaline into the blood.

4. Assertion (A) : Erythropoietin is a steroid hormone

which increases the production of RBCs.

Reason (R) : Vasopressin is a peptide hormone, stimulates growth and protein synthesis.

5. Assertion (A) :Melatonin is called “sleep hormone”. Reason (R) :Melatonin produces circadian rhythms . 6. Assertion (A) : Excess amount of a parathormone in

blood causes softening of bones.

Reason (R) : Parathormone mobilizes the release of calcium into the blood from the bones.

7. Assertion (A) :Deficiency of vasopressin causes diabetes insipidus in the patient.

Reason (R) : Vasopressin reduces the volume of urine by increasing the reabsorption of water from the urine.

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_{FEBRUARY ’13} ₁₇ 8. Assertion (A) :Glucagon converts stored glycogen into

glucose.

Reason (R) : When the blood sugar level decreases, the secretion of insulin is stimulated.

9. Assertion (A) : Failure of secretion of somatotropin

during early age causes dwarfism in the patient. Reason (R) : Somatostatin inhibits the secretion of somatotropin from anterior lobe of pituitary.

10. Assertion (A) : Thymosin is a hormone secreted by thyroid gland.

Reason (R) :Thymosin is also called “birth hormone”.

ANSWERS

1. (c)

Explanation of ‘A’ & ‘R’ :– Progesterone is a steroid hormone. It is secreted by corpus luteum. It is also secreted by placenta during pregnancy. It stimulates development of the uterine epithelium for pregnancy, implantation and formation of placenta. It also stimulates mammary glands. Progesterone is required to maintain the pregnancy, therefore hyposecretion of progesterone often causes abortion and miscarriage.

2. (a)

Explanation of ‘A’ & ‘R’:– Vitamin D is synthesized in skin epidermis from cholesterol-derived compounds in the presence of sunlight. Vitamin D exists in two forms : calciferol or D2 and cholecalciferol or D3. Cholecalciferol

is more important. It circulates in the blood. Calcitriol is active form of D3. It increases absorption of calcium

and phosphorus from chyme in the small intestine and accelerates bone formation.

3. (b)

Explanation of ‘A’ & ‘R’:– Epinephrine is called as emergency hormone. It is secreted at the time of emergency. Stimulation of the sympathetic nerves to adrenal medulla causes large quantities of epinephrine (adrenaline) and norepinephrine (noradrenaline) to be released into the blood circulation. Both the hormones, epinephrine and norepinephrine increases alertness, pupillary dilation, piloerection (raising of hairs), sweating etc. Both hormones increase the heart beat, the strength of heart contraction and the rate of respiration. However, the effect caused by epinephrine has several times as great a metabolic effect as norepinephrine. Therefore, epinephrine is referred to as emergency hormone.

4. (d)

Explanation of ‘A’ & ‘R’:– Erythropoietin is a peptide hormone, secreted by kidney. The oxygen shortage stimulates the kidney cells to secrete the hormone into the blood as a circulating glycoprotein. It stimulates the bone marrow to increase the production of RBCs (erythropoiesis). Whereas, vasopressin is a peptide hormone secreted from posterior lobe of pituitary. It is also called antidiuretic hormone because it increases the reabsorption of water in the distal convoluted tubule and collecting duct of the kidney. Somatotrophic hormone stimulates growth by stimulating protein synthesis.

5. (a)

Explanation of ‘A’ &‘R’:– Melatonin is called “sleep hormone”, because it promotes sleep. Its secretion increases in dim light an decreases in bright light. Melatonin concentration in the blood appears to flow a diurnal (day-night) cycle as it rises in the evening and through the night and drops to a low around noon. Because of this light mediated responses, it is believed to produce circadian rhythms (variation following a 24 hours cycle).

6. (a)

Explanation of ‘A’ & ‘R’ :– Parathormone, also called as Collip’s hormone is released from parathyroid gland. Parathormone (PTH) regulates calcium and phosphate balance between blood and other tissues. In case of hyperparathyroidism excess of parathormrone is secreted. Excess of PTH draws more calcium from the bones. It causes demineralisation, resulting in softening and bending of the bones. Because bones become deformed, they are easily fractured.

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_{FEBRUARY ’13} 7. (a)

Explanation of ‘A’ & ‘R’ :– Vasopressin is secreted from posterior lobe of pituitary. Vasopressin is also called as antidiuretic hormone or pitressin. It increases the reabsorption of water in the distal convoluted tubule, collecting tubule and collecting ducts of the nephrons of the kidney. In the absence or deficiency of ADH, the collecting ducts are virtually impermeable to water, and water flows out as urine. Thus, deficiency of vasopressin or antidiuretic hormone (ADH) causes diabetes insipidus i.e., excretion of large volumes of dilute urine.

8. (c)

Explanation of ‘A’ & ‘R’ :– Glucagon is secreted by the a cells of the islets of Langerhans. Glucagon acts on the cells of liver and adipose tissue. It stimulates the liver to convert stored glycogen into glucose. Glucagon is also called as anti-insulin hormone. Whereas, insulin is secreted by the b cells of the islets of Langerhans. Insulin is antagonistic to glucagon. Insulin decreases the level of glucose in the blood. It converts glucose into glycogen. When the blood sugar level drops the secretion of insulin is suppressed and when the blood sugar level increases, the secretion of insulin is stimulated.

9. (b)

Explanation of ‘A’ & ‘R’ :– Somatotropin is secreted by the anterior lobe of the pituitary gland. It stimulates the growth of the body. Dwarfism is caused by the deficiency of growth hormones from childhood. Somatostatin is secreted by the hypothalamus of the brain, delta cells of islets of Langerhans in pancreas and argentaffin cells of the digestive tract. It inhibits the secretion of growth hormone from anterior lobe of the pituitary gland. It also suppresses the release of other hormones from the pancreas and digestive tract.

10. (d)

Explanation of ‘A’ & ‘R’ :– Thymosin is a hormone secreted by thymus gland. Thymus gland is located in upper part of the thorax near the heart. Thymus gland is a soft, pinkish, bilobed mass of lymphoid tissues. It is a prominent gland at the time of birth but gradually atrophies in adult. Thymosin stimulates the development of white blood cells which are involved in producing immunity. It also hastens attainment of sexual maturity. Oxytocin is called “birth hormone” as it promotes contraction of uterine muscles during labour and help in parturition.

nn

Surgeons are the rock stars of the medical profession. Here re a few names of the most famous ones in history:

John Heysham Gibbon

He was known for the invention of the heart-lung machine, and for being the first to perform open heart surgery.

Joseph Lister

He introduced the idea of sterilizing surgical instruments with carbolic acid as well as using antiseptics to clean wounds.

Frederic E Mohs

Mohs developed the Mohs Micrographic Surgery (MMS) technique, used to remove skin cancer lesions.

Christiaan Barnard

This South African surgeon was the first person to perform a heart transplant on a human being.

Gavril Ilizarov

His speciality was orthopedic surgery and his research into bone

Ten ‘PoP’ Surgeons in History

_{development led him to invent the procedure used to this day to}

reshape or lengthen the bones in legs or arms.

Norman Bethune

This surgeon’s main claim to fame is his development of a mobile blood transfusion process.

Lars Laksell

If you have been the beneficiary of a radiosurgery treatment, then you have Lars Laksell to thank for it.

Paul Randall Harrington

The Harrington Rod, designed to help straighten the spine and keep it immobilised, is named after him. It was in use from the 1960s all the way until the late 1990s.

John Hunter

An outstanding surgeon, he was also known for his compassion, and often waived fees for his poorer patients.

Sanjay Gupta

He is probably the most well known surgeon alive in the world-partly thanks to being CNN’s medical correspondent.

nn

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_{february ’13} ₁₉ 1. Which of the following statements regarding universal rules

of nomenclature is wrong?

(a) The first word in a biological name represents the genus.

(b) The first word denoting the genus starts with a capital letter

(c) both the words in a biological name, when handwritten, are separately underlined

(d) biological names are generally in Greek and written in italics.

2. Which of the following is correct? (a) all fungi are filamentous

(b) Transfer of DNa from one bacteria to another bacteria cannot take place

(c) Virus cannot have both DNa and rNa (d) Protists reproduce asexually only.

3. Select the correct combination of the statements (i-iv) regarding the characteristics of certain organisms. (i) Methanogens are archaebacteria which produce

methane in marshy areas

(ii) Nostoc is a filamentous blue-green alga which fixes atmospheric nitrogen

(iii) Chemosynthetic autotrophic bacteria synthesize cellulose from glucose

(iv) Mycoplasma lack a cell wall and can survive without oxygen

The correct statements are

(a) (ii) and (iii) (b) (i),(ii) and (iii) (c) (ii), (iii) and (iv) (d) (i), (ii) and (iv). 4. Single-celled eukaryotes are included in

(a) protista (b) fungi (c) archaea (d) monera.

5. In which of the following classes of fungi, sexual reproduction is absent?

(a) basidiomycetes (b) Deuteromycetes (c) Phycomycetes (d) ascomycetes.

6. algae have cells made up of

(a) cellulose, galactans and mannans (b) hemicellulose, pectins and proteins (c) pectins, cellulose and proteins (d) cellulose, hemicellulose and pectins.

7. Which of the following statements is/are incorrect regarding bryophytes?

(a) Zygote undergoes meiosis to produce sporophyte (b) Zygote undergoes mitosis to form embryo proper (c) fertilization takes place in presence of water (d) Sporophyte is parasitic over gametophyte. 8. Pick out wrong statement:

(a) Double fertilization is unique to gymnosperms and monocotyledons

(b) Sequoia, a gymnosperm, is one of the tallest trees (c) Phaeophyceae members possess chlorophyll a, c,

carotenoids and xanthophylls

(d) Moss is a gametophyte which consists of two stages namely, protonema stage and leafy stage

9. aestivation of petals in the flower of cotton is correctly shown in

(a) (b)

(c) (d)

10. find the correct match.

(a) Mustard plant : leaves are opposite (b) Mustard plant : leaves are alternate (c) Guava plant : leaves are alternate (d) Guava plant : leaves are whorled

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_{february ’13}

11. Which one of the following is matched incorrectly? (a) Pinus : coralloid roots

(b) Sequoia : tap roots (c) Cycas : unbranched stem (d) Cedrus : branched stem. 12. In cyathium inflorescence

(a) single male flower is surrounded by female flowers (b) male and female flowers are borne in different plants (c) there is only one male and one female flowers (d) single female flower surrounded by many peripheral

male flowers.

13. Which one of the following is not correct?

(a) early wood is characterized by large number of xylary elements

(b) early wood is characterized by vessels with wider cavities

(c) Late wood is characterized by large number of xylary elements

(d) Late wood is characterized by vessels with narrower cavities.

14. apoplastic movement of water in plants occurs through (a) casparian strips (b) plasma membrane (c) intracellular spaces (d) plasmodesmata.

15. Cell a and cell b are adjacent plant cells. In cell a, ys = –20 bars yp = 8 bars. In cell b, ys = –12 bars and yp = 2 bars. Then,

(a) water moves from cell a to cell b

(b) there is no movement of water between cell a and cell b

(c) water moves from cell b to cell a

(d) equal amount of water is simultaneously exchanged between cell a and cell b.

16. Select the correct match.

(a) Nitrosomonas – Nitrite to nitrate (b) Thiobacillus – Denitrification

(C) Nostoc – free-living nitrogen-fixer (D) Azotobacter – anaerobic nitrogen-fixer (a) a and b (b) C and D

(c) b and C (d) b and D.

17. In C₃ cycle for the fixation of every CO₂ molecule, the reduction and regeneration steps require

(a) 3 aTP and 2 NaDPH₂ (b) 2 aTP and 2 NaDPH₂ (c) 2 aTP and 3 NaDPH₂ (d) 3 aTP and 3 NaDPH₂. 18. In the electron transport system present in the inner

mitochondrial membrane, complexes I and IV are respectively

(a) NaDH dehydrogenase and faDH₂ (b) faDH₂ and NaDH dehydrogenase

(c) NaDH dehydrogenase and cytochrome oxidase complex (d) cytochrome bc1 complex and NaDH dehydrogenase. 19. faD acts as an electron acceptor in between

(a) fumaric and malic acid (b) succinic and fumaric acid (c) malic and oxaloacetic acid (d) citric and isocitric acid

20. Which one of the following synthetic growth regulators is used to promote synchronized flowering in pineapple? (a) benzyl aminopurine

(b) Phenylmercuric acetate (c) Indolebutyric acid

(d) 2-chloroethylphosphonic acid.

21. Transfer of pollen grains from the anther to the stigma of another flower of the same plant is called

(a) xenogamy (b) geitonogamy (c) karyogamy (d) autogamy. 22.

In the diagram given above, parts labelled as ‘a’, ‘b’, ‘C’, ‘D’, ‘e’ and ‘f’ are respectively identified as

(a) synergids, polar nuclei, central cell, antipodal cell, filiform apparatus and egg

(b) polar nuclei, egg, antipodal cell, central cell, filiform apparatus and synergids

(c) egg, synergids, central cell, filiform apparatus, antipodal cell and polar nuclei

(d) central cell, polar nuclei, filiform apparatus, antipodal cell, synergids and egg.

23. Consider the following statements and select the correct option.

(a) The endomembrane system includes plasma mem-brane, er, Golgi complex, lysosomes and vacuoles. (b) er helps in the transport of substances, synthesis of

proteins, lipoproteins and glycogen. (C) ribosomes are involved in protein synthesis. (D) Mitochondria help in oxidative phosphorylation and

generation of aTP. (a) b, C and D are correct (b) a - alone is correct

(c) b - alone is correct (d) C - alone is correct. 24. If the length of a double helical DNa is 1.7 meters. The

number of base pairs present in the DNa is (a) 5 × 109 (b) 1.7 × 109

(c) 3.4 × 109 _{(d) 1.7 × 10}5_.

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_{february ’13} ₂₁ 25. Select the incorrect statement.

(a) ribozymes are nucleic acids with catalytic power. (b) Nucleic acids serve as genetic material.

(c) Proteins, nucleic acids and polysaccharides are the only three types of macromolecules found in the living system.

(d) Collagen is the most abundant protein in the whole of the biosphere and rubisCo is the most abundant proteins in animal world.

26. Select the correct option with respect to mitosis. (a) Chromatids separate but remain in the centre of the

cell in anaphase

(b) Chromatids start moving towards opposite poles in telophase

(c) Golgi complex and endoplasmic reticulum are still visible at the end of prophase.

(d) Chromosomes move to the spindle equator and get aligned along equatorial plate in metaphase. 27. When yellow round heterozygous pea plants are self

fertilized, the frequency of occurrence of rryy genotype among the offsprings is

(a) 9/16 (b) 3/16

(c) 2/16 (d) 1/16.

28. read the following statements and choose the correct option.

a. Nitrogenous base is linked to the pentose sugar through a N-glycosidic linkage.

b. Phosphate group is linked to 5’-OH of a nucleoside through phosphoester linkage.

C. Two nucleosides are linked through 3’ – 5’ N-glycosidic linkage.

D. Negatively charged DNa is wrapped around positively charged histone octamer to form nucleosome. e. The chromatin that is more densely packed and stains

dark is called euchromatin. (a) a, b and C alone are wrong (b) D alone is wrong

(c) C and e alone are wrong (d) a alone is wrong.

29. beads on string like structures of a are seen in b, which further condense to form chromosomes in C stage of cell division.

A B C

(a) Chromonema Chromatin Metaphase (b) Chromatin Chromatid Metaphase (c) Chromonema Chromosome anaphase (d) Chromonema Chromatid anaphase. 30. Which of the following statements is false regarding

predators?

(a) Predators keep prey populations under control. (b) Predators help in maintaining species diversity in a

community.

(c) If a predator is not efficient, then the prey population would become extinct.

(d) Herbivores (predators) have a greater advantage since the plants cannot run away to avoid predation. 31. Given below is an imaginary pyramid of numbers. What

could be one of the possibilities about certain organisms at some of the different levels?

TC SC PC PP 1 500 50 10

(a) Level PC is “insects” and level SC is “small insectivorous birds”.

(b) Level PP is “phytoplanktons” in sea and “whale” on top level TC

(c) Level one PP is “pipal trees” and the level SC is “sheep”.

(d) Level PC is “rats” and level SC is “cats”.

32. Which of the following relations is correct regarding GPP and NPP of an ecosystem?

(a) NPP = GPP – animal consumption (b) NPP = GPP + Plant respiration (c) NPP = GPP – Plant respiration (d) NPP = GPP + animal consumption. 33. Select the incorrect statement.

(a) Species diversity increases as we move away from the equator towards the poles.

(b) Stellar’s sea cow and passenger pigeon got extinct due to over exploitation by man.

(c) Lantana and Eichhornia are invasive weed species in India.

(d) among animals, insects are the most species-rich taxonomic group.

34. Match the items of column I with column II and select the correct option.

Column I Column II

a. electrostatic 1. removes gases like SO₂ precipitator

b. Scrubber 2. reduces automobile emission C. Catalytic 3. removes particulate matter

converter

(a) a – 2, b – 3, C – 1 (b) a – 3, b – 2, C – 1 (c) a – 1, b – 2, C – 3 (d) a – 3, b – 1, C – 2. 35. Which of the following is a correct match between crop,

variety and resistance to diseases?

Crops Variety Resistance to

diseases

(a) Wheat Himgiri White rust (b) Brassica Pusa sadabahar black rot (c) Cowpea Pusa komal bacterial blight (d) Chilli Pusa swarnim Chilly mosaic virus

Biology Today 2013-02

Contents

A miracle in medical research

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ANSWERS

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ANSWERS

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Ten ‘PoP’ Surgeons in History

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