Biology 2018

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Question Paper with Complete Solution

1. What is implantation?

Ans: The process in which the blastocyst gets embedded in the endometrium wall of the uterus is called implantation.

2. Write the restriction site for EcoRI enzyme.

Ans: 

5'-GAATTC-3'
3'-CTTAAG-5'

3. Define ‘Totipotency’.

Ans: The capacity of a cell explant to grow into a whole plant is called totipotency.

4. Mention the role of Methanobacterium in rumen of cattle.

Ans: Methanobacterium found in the rumen of cattle helps in the digestion of cellulose and its breakdown into glucose.

5. What is Foetal Ejection Reflux?

Ans: Parturition signals originate from the fully developed foetus and the placenta which induce mild uterine contractions called foetal ejection reflex.

6. Define ‘Saltation’.

Ans: Single-step large mutation which causes speciation is called saltation.

7. Name the type of antibodies produced during allergy.

Ans: Immunoglobulin E  (IgE) antibodies are produced in response to allergens.

8. What are Eurythermal animals?

Ans: The organisms tolerating the high range of temperature are called eurythermal animals. 

9. Define Biomagnification.

Ans: Biological magnification or biomagnification is defined as an increase in the concentration of toxicants at successive trophic levels.

10. Write the name of toxic substance responsible for fever and chills in malaria.

Ans: Haemozoin.

11. What are homogametes and heterogametes?

Ans: Male and female gametes which are similar in appearance and it is not possible to differentiate between them, they are called homogametes or isogametes.

The male and female gametes that are morphologically distinct, they are called heterogametes.

12. Mention any two examples of evolution by anthropogenic action.

Ans: 

a. Industrial melanism:

In England, before industrialization, white-winged moths were more in number than dark-winged moths. But after industrialization, dark-winged moths became more in number than white-winged moths. This is because, during industrialization, the tree trunks covered by white lichens became dark due to the deposition of dust and coal particles. As a result, white-winged moths could be easily picked up by the predators from the dark background and dark-winged moths survived.

 

b. Chemical resistance:

Excessive use of herbicides and pesticides has resulted in the evolution of resistant varieties of microbes in much lesser time scale. As a result, pathogenic bacteria are appearing in a very short period.

 

13. Distinguish between homozygous and heterozygous plants.

Ans: Homozygous condition is a situation of a plant in which a particular character is controlled by a pair of similar genes.

A heterozygous condition is a situation of a plant in which a particular character is controlled by alleles which express contrasting traits.

14. What is innate immunity? Mention any two types of innate immunity barriers.

Ans: Innate immunity is a non-specific type of defense present at the time of birth. It is accomplished by providing different types of barriers. They are,

a. Physical barriers

b. Physiological barriers

c. Cellular barriers

d. Cytokine barriers

15. Which are the important components of Poultry Farm Management?

Ans: Poultry farm management includes;

Suitable breeds, adequate water, a proper place.

a. Selection of disease-free, suitable breeds.

b. Proper and safe farm conditions.

c. Proper food and water.

d. Hygiene and health care of the birds.

16. Write the methods to introduce alien DNA into host cells.

Ans: 

a. Chemical (electroporation) method: The cell is treated with a specific concentration of a divalent cation such as calcium to increase pore size in the cell wall. The cells are incubated with recombinant DNA on ice, followed by placing them briefly at 42 °C and then putting it back on ice. This is called heat shock treatment. The bacteria now take up the recombinant DNA.

b. Micro-injection method: Recombinant DNA is directly injected into the nucleus of an animal cell.

c. Biolistics or gene gun method: Cells are bombarded with high-velocity micro-particles of gold or tungsten coated with DNA in plants.

17. Define endemism. Name any two regions of accelerated habitat loss in India.

Ans: Endemism is the state of a species being found in a single defined geographical area and not found anywhere else in the world.

The regions of accelerated habitat loss in India are;

a. Western ghats and Srilanka.

b. Indo Burma and Himalaya.

18. Invasion of animal species eliminates the native animal species - give two examples.

Ans:

Nile perch, a large predator fish when introduced in Lake Victoria (East Africa) caused the extinction of an ecologically unique species of Cichlid fish in the lake.

Invasive weed species like Parthenium (carrot grass), Lantana, and Eichhornia (water hyacinth) caused environmental damage and posed threat to our native species.

19. Mention the vegetative propagules of the following plants:

a) Water Hyacinth

b) Agave

c) Banana

Ans: 

a) Water Hyacinth - Offset

b) Agave - Bulbil

c) Banana - Rhizome

 

20. Draw a neat labeled diagram of T. S. of the young anther.

Ans:

Anther W.png

21. Describe Haplodiploid sex determination system Honey Bees.

Ans: 

  • Honeybee show a haploid sex-determination system.

  • Offsprings formed from the union of a sperm and an egg develop a female (queen or workers), which are diploid, having 32 chromosomes.

  • Unfertilized eggs developed by parthenogenesis form males (drone), which are haploid having 16 chromosomes.

  • Male produce sperms by Mitosis, so they, neither have fathers nor sons but have grandfathers and grandsons.

22. State Hardy-Weinberg principle of genetic equilibrium. Write any four factors affecting the equilibrium.

Ans: Hardy-Weinberg principle states that allelic frequencies in a population are stable and remain constant from generation to generation, i.e., gene pool (total number of genes and their alleles in a population) is constant.

Evolutionary factors like gene migration (gene flow), genetic drift, mutation, genetic recombination affect the equilibrium.


23. Write a short note on ecosystem services.

Ans:

a. Ecosystems (forests) purify air and water.

b. Cycle nutrients.

c. Provide wildlife habitat.

d. Pollinate crops.

e. Mitigate droughts and floods.

f. Generate fertile soils.

g. Maintain biodiversity.

h. Provide storage site for carbon.

i. Provide aesthetic, cultural, and spiritual values.


24. Sketch the diagrammatic representation of the Replication of Retrovirus inside an animal cell.

Ans:

Retrovirus W.png

25. What is ecological succession? How hydrarch succession is different from Xerarch succession?

Ans: The sequential, gradual, and predictable changes in the species composition in an area are called succession or ecological succession.

Hydrarch succession: The plant succession which takes place in a wet area or water, leading to a successional series of progress from hydric to mesic conditions.

 

Xerarch succession: The plant succession which takes place in a dry area, leading to a successional series from xeric to mesic conditions.

26. Draw a neat labeled diagram of plasmid pBR322.

Ans:

pBR322 wix.png

27. Draw and describe the structure of mature embryo sac of angiosperms.

Ans:

Embryo sac W.png

28. Draw a neat labeled, diagrammatic sectional view of the female reproductive system.

Ans:

Female Reproductive System wix.png

28. Explain the Inheritance of one gene with reference to the stem height of the Garden Pea plant.

Ans: The crossing between two plants, with respect to a single contrasting character is called monohybrid cross.

  • Mendel conducted hybridization experiment by crossing true-breed tall pea plant (TT) with true-breed dwarf pea plant (tt).

  • In F1 (First filial) generation only one of the parental traits (tall) was seen and the trait of another plant (dwarf) was not seen.

  • Mendel self-pollinated the tall F1 plants and he found that in the F2 generation some of the offspring were ‘dwarf’; the character that was not seen in the F1 generation was now expressed.

  • The proportion of plants that were dwarf was 1/4th of the F2 plants while 3/4th of the F2 plants were tall.

  • F2 plants were identical to their parental type and did not show any blending.

29.

a) What are the features of an ideal contraceptive?

b) Mention the natural methods of contraception.

Ans: 

a) An ideal contraceptive should be:

  • User-friendly.

  • Easily available.

  • Effective and reversible with no or least side effects.

  • non-interfering with the sexual drive/desire and/or the sexual act of the user.

b) Natural methods of contraception include:

  • Periodic abstinence

  • Coitus interrupts or withdrawal

  • Lactational amenorrhea

31. Explain the following terms:

a) Inbreeding depression

b) Interspecific hybridization

c) Biofortification

d) Micropropagation

e) Somaclones

Ans:

a) Inbreeding depression: The condition in which close inbreeding usually results in a reduction of fertility and productivity. This is called inbreeding depression.

b) Interspecific hybridization: It refers to crossing between male and female animals of two different related species.

c) Biofortification: It is the method for developing crops with higher levels of vitamins, minerals, proteins and healthier fats to improve public health.

d) Micropropagation: The method of growing or producing thousands of plants through tissue culture is called micropropagation.

e) Somaclones: Plants produced by the micropropagation are morphologically and genetically identical to their original plants. Such plants are called somaclones.

32. Explain the regulation of Lac Operon in the absence and presence of Lactose as an inducer.

Ans:

  • Lac Operon consists of regulatory genes, and structural genes lac zya.

  • Control genes consists of promoter. Between promoter and structural genes is the operator.

  • Regulatory gene lac I codes for repressor, which binds to operator and switches off oflac Operon.

  • When glucose not available, lactose available Lactose enters E.coli and binds inducer and forms inducer repressor complex that frees the operator.

  • RNA polymerase will transcribe the structural gene produce polycistronic mRNA now lac Operon is switched on.

  • Polycistronic mRNA is translated into three enzymes; beta galactosidase-by lac Z, betagalactosidepermease - by lac Y and betagalactosidetransacetylase - by lac A.

Lacoperon W.png

33. Oswald Avery and others have contributed Griffith’s transforming principle to prove DNA as genetic material – substantiate.

Ans: 

  • In 1928, Frederick Griffith conducted a series of experiments with Streptococcus pneumoniae [a bacterium causing pneumonia].

  • He observed miraculous transformation in the bacteria during the course of his experiment, living organism (bacteria) had changed in physical form.

  • When bacterium grown on a culture plate, some produce smooth shiny colonies (S-strain) with mucous (polysaccharide) coat, while other produce rough colonies (R-strain) without coat or capsule.

  • When live S-strain bacteria were injected into mice, they died due to pneumonia.

  • When live R-strain bacteria injected into mice, they survived.

  • When heat killed S-strain bacteria were injected into mice, they survived and there were no symptoms of Pneumonia.

  • When he injected a mixture of heat killed S and live R-strain bacteria into mice, they died due to unexpected symptoms of Pneumonia and he recovered living as bacteria from the dead mice.

  • He concluded that R-strain bacteria had somehow been transformed by the heat killed Sstrain bacteria. Some transforming principle, transferred from the heat killed S-strain, had enabled the R-strain to synthesise a smooth polysaccharide coat and become virulent. But he was not able to understand the cause of this bacterial transformation.

  • Oswald Avery, Colin McLeod and Maclyn McCarty repeated Griffith's experiment in order to determine biochemical nature of transforming principle.

  • They concluded that DNA from the heat killed S-strain bacteria caused the transformation of non-violent R-strain bacteria into virulent S-strain bacteria.

  • They also discovered that proteases and RNases did not affect transformation while DNases Inhibited the process and they concluded that DNA is the hereditary material.

34. Describe the role of Microbes in the sewage treatment plant.

Ans: 

  • After sequential filtration primary effluent is passed into large aeration tanks with constant mechanical agitation and air supply.

  • Useful aerobic microbes grow rapidly and form flocs.

  • Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures.

  • The growing microbes consume organic matter and thus reduce the biochemical oxygen demand (BOD).

  • When the BOD of sewage has reduced, the effluent is passed into settling tank.

  • Here, the bacterial flocs settle, and the sediment is called activated sludge.

  • A small part of the sludge is used as an inoculum in the aeration tank and the remaining part is passed into large tanks called anaerobic sludge digesters.

  • In the digesters, other kinds of bacteria, which grow anaerobically, digest bacteria and fungi in sludge.

  • During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide, and C02 which form the biogas.

35. One of the applications of biotechnology is to get pest-resistant plants - Justify the statement with reference to Bt cotton.

Ans: 

  • Some strains of Bacillus thuringiensis produce proteins that kill some insects like lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes).

  • B. thuringiensis forms protein crystals which contain a toxic insecticidal protein.

  • Bt toxins are initially inactive protoxins but after ingestion by the insect their inactive toxin becomes active due to the alkaline pH of the gut, which solublises the crystals.

  • The activated toxin binds to the surface of midgut epithelial cells thus creating pores which causes cell swelling and lysis, further leading to death of the insects.

  • Specific Bt toxin genes obtained from Bacillus thuringiensis are used in several crop plants like cotton.

  • The toxin is coded by a gene called cry which is of various types. For example, proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms and that of cryIAb control corn borer.

  • Bt tobacco was first cultured to kill hornworm (Manduca sexta).

36.

a) What are Ectoparasites and Endoparasites? (2)

b) List any three parasitic adaptations in animals. (3)

Ans: a) 

  • Ectoparasites: These are the parasites which feed on the external surface of the host organism for food and shelter. E.g. Lice on humans, ticks on dogs, copepods, Cuscuta.

  • Endoparasites: These are the parasites which live inside the host's body at different sites like liver, kidney, lungs, etc., for food and shelter. E.g. tapeworm, liver fluke, Plasmodium.

b) Adaptation of parasite:

  • The parasite has evolved to be host-specific in such a manner that both host and parasite tend to co-evolve.

  • Loss of unnecessary sense organs.

  • Presence of adhesive organs or suckers.

  • Loss of digestive system.

  • High reproductive capacity.

37. Write a note on the following: a) Radioactive wastes b) Joint forest management.

Ans: 

a) Nuclear energy was assumed to be a natural, non-polluting way of electricity generation till the incidents at Three Mile Island and Chernobyl. It is now considered as the most potent pollutant.

Causes: Leakage of radioactive materials from power plants. Unsafe disposal of radioactive wastes.

Harmful effects: Radiations from nuclear wastes cause mutations at a very high rate. In high doses, nuclear radiations are lethal. In low doses, radiations cause disorders and cancer.

b) In 1980, the Government of India has introduced the concept of 'Joint Forest Management' (l FM) to work closely with the local communities for protecting and managing forests on mutual benefits.