Biology 2019
Question Paper with Complete Solution
PART - A
Answer the following questions in one word or one sentence each;
1. Name the reproductive cycle that occurs in non-primates.
Ans: Oestrus Cycle
2. Name the layer of the uterus that exhibits strong contractions during parturition.
Ans: The myometrium exhibits strong contraction during the delivery of the baby.
3. Which chromosome of man has the least number of genes?
Ans: 'Y' chromosome
4. Write the infectious form of plasmodium which enter the human body through a mosquito bite.
Ans: 'Sporozoite'
5. Give an example for an inter-specific hybrid animal.
Ans: Mule – The mule is a progeny of a female horse and a male donkey.
6. Write the scientific name of the source organism for citric acid.
Ans: Aspergillus niger
7. Mention a gene that codes for an insecticidal protein in Bt cotton.
Ans: cry II Ab
8. Name the plasmid present in Agrobacterium tumefaciens.
Ans: Agrobacterium tumefaciens cell contains a plasmid known as the Ti (tumor-inducing) plasmid.
9. What is the main aim of the Montreal protocol?
Ans: To check the emission of ozone-depleting substances.
10. Name the type of food chain that is the major conduit for energy flow in an ecosystem.
Ans: Grazing food chain (GFC)
PART - B
Answer any five of the following questions in 3 to 5 sentences each wherever applicable;
11. What is embryogenesis? Mention two important events that occur during embryogenesis.
Ans: The process of development of an embryo from the zygote.
Two important events that occur during embryogenesis are cell division and cell differentiation.
12. Define point mutation. Give an example for point mutation.
Ans: Point mutation is a change in a single base pair of DNA by substitution, deletion, or insertion of a single nitrogenous base.
An example of point mutation is sickle cell anaemia. It involves a mutation in a single base pair in the beta-globin chain of haemoglobin pigment of the blood.
13. What are the conclusions drawn by T. H. Morgan from the crossing experiments in Drosophila with respect to linkage?
Ans: The conclusions drawn by T.H. Morgan from the crossing experiment in Drosophila with respect to linkage were-
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The gene responsible for eye colour is located on X chromosome.
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The alleles responsible for eye colour are present on X chromosome.
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There are two X chromosomes in females. Both X chromosomes carry an allele of the trait.
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Females can be homozygous or heterozygous for the alleles.
14. What is an allergy? Name the two chemicals released by mast cells in the body during allergy.
Ans: The exaggerated or hypersensitive reaction of the immune system to certain antigens present environment is called allergy.
Chemicals like histamine and serotonin are released from the mast cells.
15. Mention the four traits for which plant breeding is done.
Ans:
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Increased crop yield
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Improve quality
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Increased tolerance to environmental stresses (salinity, extreme temperature, and drought)
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Resistant to pathogens ( viruses, fungi, and bacteria)
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Increase tolerance to insect pest
16. With an example, explain the convention for naming restriction endonucleases scientifically.
Ans: In the name of restriction endonuclease, the first letter is derived from the genus name and the next two letters from the species name of the prokaryotic cell from which they were isolated. The roman numbers, following the names, indicate the order in which the enzymes were isolated from the bacterial strain.
Example: EcoRI is derived from Escherichia coli RY 13, the letter ‘R’ derived from the name of the strain.
Hind II from HaemophiIus influenzae Rd, BamH I from Bacillus amyloliquefaciens H, EcoR II from E. coli R245, etc.
17. A prey develops a defense against a Predator, justify the statement. With two examples in animals.
Ans:
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To avoid being detected easily by predators, some species of insects and frogs are cryptically coloured (camouflaged).
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The Monarch butterfly is highly distasteful to its predator (birds) because of a special chemical present in its body which is acquired by the butterfly by feeding on a poisonous weed in its caterpillar stage.
18. Mention any two mechanisms of how the human body compensates for low oxygen availability at higher altitudes.
Ans: The body compensates for low oxygen availability by:
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Increasing RBC's production,
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Increasing breathing rate and
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Decreasing binding affinity of Hb.
PART - C
Write any five of the following questions in about 40 to 80 words each wherever applicable;
19. Write three advantages offered by the seeds to angiosperms.
Ans: Seeds offer the following advantages to angiosperms:
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They provide nourishment and parental care to the developing embryo,
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They protect the embryo from harsh environmental conditions.
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They generate new genetic combinations leading to variations.
20. Draw a neat labeled diagram of the sectional view of the human mammary gland.
Ans:
21. DNA is a better genetic material than RNA. Justify the statement with three comparative reasons.
Ans:
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Structurally and chemically DNA is more stable than RNA.
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DNA mutates slowly, but RNA mutates fast.
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2-OH group present in RNA is a reactive group and makes RNA labile and easily degradable.
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DNA is less reactive than RNA.
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The presence of thymine at the place of uracil gives additional stability to DNA.
22. Enumerate on convergent and divergent evolution with suitable examples in plants.
Ans:
Different structures evolve for the same function and hence have similarities. This is called convergent evolution.
For example, the Wings of butterflies and birds.
Some structures developed along different directions due to adaptations to different needs. This is called divergent evolution.
For example, the forelimbs of some animals like Whales, bats, cheetahs, and humans have similar anatomical structures i.e., humerus, radius, ulna, carpals, metacarpals, and phalanges.
23. What are carcinogens? Mention any two groups of carcinogens with one example for each.
Ans: The cancer-causing agents are called carcinogens.
Carcinogens are of the following types:
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Chemical agents: Aniline dyes, N-nitrosodimethylamine, benzopyrene, chemicals in cigarette smoke.
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Physical agents: Ionising radiations like X-rays and gamma-rays, non-ionising radiations like UV-rays.
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Biological agents: Oncogenic viruses, some parasites.
24.
a) Mention four tools required for Recombinant DNA technology. (2)
b) With reference to gel electrophoresis, what is elution? (1)
Ans: The key tools required for recombinant DNA technology are:
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Restriction enzymes
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Ligases
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Host organism/cell
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Polymerase enzymes
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Vectors
25. Ecological pyramids have limitations. Justify the statement with three reasons.
Ans:
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It does not take into account the same species belonging to two or more trophic levels.
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It assumes a simple food chain that is rare in nature.
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It does not accommodate a food web.
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Saprophytes (decomposers) are not given any place in ecological pyramids.
26. Describe three factors which affect on decomposition.
Ans:
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The decomposition rate is slow if detritus is rich in lignin and chitin.
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The decomposition rate is higher when detritus is rich in nitrogen and water-soluble substances like sugars.
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A warm and moist environment favors decomposition.
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Low temperature and anaerobiosis inhibit decomposition.
PART - D
Section - I
Answer any four of the following questions in about 200 to 250 words each wherever applicable;
27. What is megasporogenesis? explain the development of 8 nucleate embryosac in flowering plants.
Ans: The formation of female gametophyte (embryo sac) is called megagametogenesis.
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Megaspore is the first cell of the female gametophyte.
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The megaspore increases in size and its nucleus divide mitotically into two nuclei which move apart to opposite poles. Thus, a 2-nucleate embryo sac is formed.
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The two daughter nuclei undergo another mitotic division giving rise to the 4- nucleate stage.
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The third mitotic division gives rise to an 8-nucleate 7-celled embryo sac.
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The central cell contains 2 nuclei known as polar nuclei.
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The three nuclei at the micropylar region form the egg apparatus.
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In the egg apparatus, the middle cell is the largest and is called oosphere/egg/ovum, while the other two naked cells adjoining the egg cell are called synergids.
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The three nuclei at the chalazal end are surrounded by cytoplasm and cellular wall. These are called antipodal cells.
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The above-mentioned method of female gametophyte formation is known as the normal 8-nucleate type because 8 nuclei contribute to the formation of gametophytes. It is very common among angiosperms.
28. What are contraceptives? Explain four different non-surgical contraceptive methods.
Ans: The devices or drugs or methods serving to prevent pregnancy (control the birth) are called contraceptives.
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Natural/traditional methods - Periodic abstinence, Coitus interrupts, Lactational amenorrhea.
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Barrier methods - These methods prevent the contact of sperm and ovum with the help of barriers. such methods are available for both males and females. Examples - Condoms, Diaphragms, cervical caps, and vaults.
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Intrauterine devices (IUDs) - These devices are inserted by doctors or expert nurses into the uterus through the vagina. Examples - Copper releasing IUDs, Hormone releasing IUDs.
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Oral contraceptive - This involves the uptake of hormonal preparations of either progestogens or progestogenestrogen combinations in the form of pills by females.
29. What is incomplete dominance? Explain it with reference to flower colour in Snapdragon.
Ans: It’s a phenomenon in which the F1 hybrid exhibits intermediate characters of the parental gene.
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It is seen in flower colours of Mirabilis jalapa (4 O'clock plant and Antirrhinum majus (Snapdragon).
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In a cross between true-breeding red flowered (RR) and true breeding white-flowered plants (rr), the F1 (Rr) was pink. When the F1 was self-pollinated the F2 resulted in the following ratio 1 Red (RR) : 2 Pink (Rr) : 1 White (rr). Here the phenotypic ratio deviates from Mendel's monohybrid cross.
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Both phenotypic and genotypic ratios will be the same 1:2:1.
30.
a) Explain the role of three organisms as biocontrol agents. (3)
b) What is the significance of BOD? (1)
c) Give an example for a fungus found in mycorrhiza. (1)
Ans: a)
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Ladybirds and Dragonflies are used to get rid of aphids and mosquitoes.
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The bacteria Bacillus thuringiensis (Bt) are used to control butterfly caterpillars.
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Trichoderma sps., free-living fungi, are present in root ecosystems where they act against several plant pathogens.
b) BOD measures the amount of oxygen consumed by microorganisms for the process of decomposition of the organic matter in the water bodies.
It indicates the amount of organic pollution present in an aquatic ecosystem.
c) Glomus
31. Explain five benefits of creating transgenic animals.
Ans:
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Transgenic animals are useful to study gene regulation, their effect on the normal functions of the body, and their development.
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To study of genes that are responsible for diseases in human and their treatment.
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Useful biological products can be produced by introducing, into transgenic animals, the portion of DNA (or genes) that codes for a particular product. For example, human protein (α-1-antitrypsin) is used to treat emphysema.
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Transgenic mice are developed to test the safety of vaccines, before being used on humans.
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Transgenic animals are made to carry genes, which makes them more sensitive to toxic substances than non-transgenic animals.
32.
a) Tropical region has greater biodiversity than temperate region. Justify the statement with three reasons. (3)
b) The use of CNG is better than petrol or diesel give four reasons. (2)
Ans: a)
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Unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification.
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Tropical environments, unlike temperate ones, are less seasonal, relatively more constant, and predictable, promoting niche specialization and leading to greater species diversity.
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There is more solar energy available in the tropics, which contributes to higher productivity.
b) Advantages of CNG
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CNG burns most efficiently.
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Very little remain unburnt.
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Cannot be siphoned
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Cannot be adulterated like petrol or diesel.
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CNG is cheaper than petrol and diesel.
Section - II
Answer any three of the following questions in about 200 to 250 words each wherever applicable;
33. a) Write the schematic representation of spermatogenesis. (3)
b) Write the two events that occur in the ovary and uterus during the follicular phase of the menstrual cycle. (2)
Ans: The follicular phase is also called the proliferative phase. During this phase, the following changes occur;
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The primary follicles in the ovary grow and become fully mature Graafian follicles.
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The endometrium of the uterus is regenerated due to the secretion of LH and FSH from the anterior pituitary and ovarian hormone, estrogen.
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It lasts for about 10 to 14 days.
34. DNA replication is said to be semiconservative why describe the experimental proof of Messelson and Stahl to show DNA replication is semiconservative?
Ans: In both the daughter DNA molecules one strand is parental and another is newly synthesized. Hence, DNA replication is called Semi Conservative.
It was first shown by Matthew Meselson and Franklin Stahl (1958) in Escherichia coli and subsequently in the higher organisms. It is popularly known as Meselson and Stahl Experiment.
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They grew E.coli in an NH4Cl medium for many generations. (TMN is a heavy isotope of nitrogen)
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The result was that N was incorporated into newly synthesized DNA and another nitrogen-containing compound as well.
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This heavy DNA molecule could be distinguished from normal DNA by centrifugation in a caesium chloride (CsCl) density gradient.
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Then they transferred the E.coli into a medium with normal 15NH4Cl15NH4Cl and let them grow. (E.coli divides in 20 minutes)
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They took samples at definite time intervals as the cells multiplied, and extracted the DNA that remained as double-stranded helices.
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Various samples were separated independently on CsCl gradients to measure the densities of DNA.
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The DNA that was extracted from the culture one generation after the transfer from 15N15N to 14N14N medium had a hybrid or intermediate density.
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DNA is extracted from the culture after another generation(after 40 min). was composed of an equal amount of this hybrid DNA and light DNA.one generation after the transfer from ..N to "N medium had a hybrid or intermediate density.
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DNA extracted from the culture after another generation (after 40 min.) was composed of an equal amount of this hybrid DNA and of light DNA.
35.
a) Draw a neat labeled diagram of Miller's experiment. (3)
b) Mention two assumptions of Oparin and Haldane with reference to the origin of life. (2)
Ans: b)
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The first form of life originated from pre-existing non-organic molecules like RNA, and proteins.
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The formation of life was preceded by chemical evolution that resulted in the formation of diverse organic molecules from inorganic constituents.
a)
36. Name the technology that can successfully increase the herd size of cattle in a short time and explain the steps involved in this technology.
Ans: Multiple Ovulation Embryo Transfer Technology (MOET)
It is a program for herd improvement in animals like cattle, sheep, rabbits, buffaloes, mares, etc...,
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In this method. a cow is administered hormones, with FSH-like activity, to induce follicular maturation and super-ovulation.
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The cow produces 6—8 eggs instead of one egg produced normally.
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It is now, either mated with an elite bull or artificial insemination is carried out.
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When the fertilized eggs attain the 8—32 cells stage, they recovered non-surgically and are transferred to a surrogate mother.
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The genetic mother can now be again super-ovulated.
37.
a) Mention four ‘Evil Quartet’ which caused depletion of biodiversity. (2)
b) Write two suspended activities in animals against abiotic stresses with suitable examples. (2)
c) Among vertebrates which group of animals has the highest number in global biodiversity? (1)
Ans: a)
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Habitat loss and fragmentation
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Over-exploitation
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Alien (exotic) species invasion
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Co-extinctions
b)
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Hibernation - winter sleep. Eg-polar bear.
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Aestivation- summer sleep. Eg- frog, snail.
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Diapause - suspended development.
c) Fishes constitute the highest diversity among the vertebrates.