Biology 2020

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Question Paper with Complete Solution

PART - A

Answer the following questions in one word or one sentence each;

1. How many chromosomes are there in meiocytes of human beings?

Ans: Human Meiocytes (diploid) – 46

2. Name the inducer which regulates the switching on and off lac operon.

Ans: Lactose

3. Which type of R.N.A polymerase enzyme transcribes precursor m.R.N.A?

Ans: RNA polymerase II

4. Name the part of the flower which develops into the fruit after fertilization.

Ans: 'Ovary'

5. Write the scientific name of the fungus which produces cyclosporine A.

Ans: Trichoderma polysporum

6. What are pioneer species?

Ans: The species that invade a bare area are called pioneer species.

7. Which bacteria is commonly found in the anaerobic sludge during sewage treatment?

Ans: Methanogens

8. Name the international treaty which controls the emission of ozone-depleting substances.

Ans: Montreal Protocol

9. Define endemism.

Ans: Ecological state of a species that is confined to a particular geographical area.

10. What are euryhaline organisms?

Ans: Organisms that can tolerate and thrive of a wide range of salinities are called euryhaline organims.

 

PART - B

Answer any five of the following questions in 3 to 5 sentences each wherever applicable;

11. Name the scientist who found out D.N.A. and what was the name given by him?

Ans: Friedrich Meischer in 1869, and He termed it as ‘Nuclein’.

12. Write the accessory ducts found in the male reproductive system.

Ans: The male sex accessory ducts include rete testis, vasa efferentia, epididymis, and vas deferens.

13. Mention the genotype of the parents when their children are with A, B, AB, O blood groups.

Ans: IA i, IB i

14. Name the two hormone-releasing IUDs.

Ans: Progestasert and LNG-20

15. What are the two types of disorders of humans where the karyotype is 47?

Ans: ​Down’s syndrome (45+XX, 45+XY) and Klinefelter's syndrome (44+XXY).

 

16. Name the two primates those were existing in 15 mya.

Ans: Dryopethecus and Ramapithecus

17. Mention the two diseases resisted by mungbean through mutation breeding.

Ans: ​Yellow mosaic virus and powdery mildew.

18. Write the two basic amino acid residues which are rich in histones.

Ans: Lysine and Arginine

PART - C

Write any five of the following questions in about 40 to 80 words each wherever applicable;

19. Mention the asexual reproductive structures of the following:

a. Penicillium

b. Hydra

c. Sponges

Ans: 

a. Penicillium - Conidia

b. Hydra - Buds

c. Sponges - Gemmules

20. Sketch and label Miller's experiment.

Ans:

 
Miller's wix.png

21. Name the diseases caused by the following organism:

a. Rhino virus

b. Wuchereria bancrofti

c. Haemophilus influenzae

Ans:

​a. Rhino virus – Common cold

b. Wuchereria bancrofti – Filariasis / Elephantiasis

c. Haemophilus influenzaa – Pneumonia

22. Define infertility. Write two assisted reproductive technology to overcome infertility.

Ans: Infertility is the inability to produce children in spite of unprotected sexual cohabitation.

 

ART technologies are:

  1. Test tube baby programme – IVF, ZIFT

  2. Gamete intrafallopian transfer (GIFT)

  3. Intra cytoplasmic sperm injection (ICSI)

  4. Artificial insemination (AI)


23. Schematically represent the phosphorus cycle.

Ans:

Phosphorous Cycle.png

24. What is ecological succession? How hydrarch succession is different from that of 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 successional series progress from hydric to the mesic conditions.

 

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

25. Alien species invasion caused the decline or extinction of indigenous species. Justify the statement by giving three examples.

Ans: Some alien (exotic) species when introduced unintentionally or deliberately, become invasive and cause harmful impact, resulting in the extinction of the indigenous species.

Examples:

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

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

  3. The introduction of African catfish (Clarias gariepinus) for aquaculture purposes is posing a threat to the indigenous catfishes of Indian rivers.

26. Define autogamy. Write the two different kinds of flowers that exhibit autogamy.

Ans: It is a type of pollination in which pollens are transferred to the stigma of the same flower.

E.g., wheat, rice, pea, etc…

 

hasmogamous and Cleistogamous flowers exhibit autogamy.

PART - D

Section - I

Answer any four of the following questions in about 200 to 250 words each wherever applicable;

27. Explain a mature embryo sac with a neat labelled diagram.

Ans: 

  1. The embryo sac is referred to as a female gametophyte.

  2. The formation of a female gametophyte (embryo sac) is called megagametogenesis.

  3. 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.

  4. The two daughter nuclei undergo another mitotic division giving rise to the 4-nucleate stage.

  5. The third mitotic division gives rise to an 8-nucleate 7-celled embryo sac.

  6. The central cell contains 2 nuclei known as polar nuclei.

  7. The three nuclei at the micropylar region form the egg apparatus.

  8. 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.

  9. The three nuclei at the chalazal end are surrounded by cytoplasm and cellular wall. These are called antipodal cells.

 
Embryo sac W.png

28. Schematically represent the inheritance of two genes in pea plants with reference to seed colour and shape.

Ans:

Dihybrid cross.png

29. Mention five salient features of Human Genome Project.

Ans:  Salient features of Human Genome Project (HGP):

  1. The Human Genome contains 3164.7 million bases pairs.

  2. The average gene consists of 3000 bases; the largest known human gene being dystrophin at 2.4 million bases.

  3. The total number of genes is estimated to be 30,000 and 99.9% nucleotide bases are exactly the same in all people.

  4. The functions are unknown for over 50% of the discovered genes.

  5. Less than 2% of the genome codes for proteins.

  6. The Human genome contains large repeated sequences.

  7. The repeated sequence is thought to have no direct coding functions, but they throw light on chromosome structures, dynamics and evolution.

  8. Chromosome 1 has most genes (2968) and the Y has the fewest genes (231).

  9. Scientists have identified about 1.4 million locations where single base DNA sequence differences called single nucleotide polymorphism or SNPs occur in humans.

30.

a. Define immunity and name two different types of immunity. (3)

b. Draw a neat labelled diagram of the structure of an antibody molecule. (2)

Ans:

a) The overall ability of the host to fight the disease-causing organisms is called immunity.

 

Immunity is of two types:

  • Innate immunity

  • Acquired immunity

b) 

Antibody Molecule W.png

31. With reference to tissue culture explain the following terms:

a. Explant

b. Totipotency

c. Micropropagation

d. Somaclones

e. Somatic hybrids

Ans:

  1. Explant - The part of the plant taken for tissue culture is called explant.

  2. Totipotency - The capacity of a cell explant to grow into a whole plant is called totipotency.

  3. Micropropagation - The method of growing or producing thousands of plants through tissue culture is called micropropagation.

  4. Somaclones - The plants produced from tissue culture are genetically identical to the original plant from which they are grown, so they are called somaclones.

  5. Somatic hybrids - The process of fusion of protoplast of somatic cells obtained from different varieties or species of plant on a suitable nutrient medium in vitro to develop a somatic hybrid is called somatic hybridization. And hybrids are called somatic hybrids.

32. Explain briefly how transgenic animals benefit the human beings.

Ans: 

  • Transgenic animals are useful to study gene regulation, their effect on the normal functions of the body, and their development.

  • To study of genes that are responsible for diseases in human and their treatment.

  • 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.

  • Transgenic mice are developed to test the safety of vaccines, before being used on humans.

  • Transgenic animals are made to carry genes, which makes them more sensitive to toxic substances than non-transgenic animals.

 

Section - II

Answer any three of the following questions in about 200 to 250 words each wherever applicable;

33. Draw a neat labeled diagram of a sectional view of the female reproductive system.

Female Reproductive Structure 1.png