Biology Paper 1 (Theory)

Maximum Marks: 70 Time Allotted: Three Hours

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Section A – 20 MARKS

Question 1

(i) A patient is diagnosed with elephantiasis. Name the causative agent.

• (a) Wuchereria bancrofti
• (b) Plasmodium vivax
• (c) Salmonella typhi
• (d) Rhinoviruses

(ii) If a colour-blind man marries a woman who is homozygous for normal colour vision, the probability of their son being colour-blind is:

• (a) 0%
• (b) 25%
• (c) 50%
• (d) 100%

(iii) The part of the flower that develops into a fruit is the:

• (a) Ovary
• (b) Ovule
• (c) Stamen
• (d) Petal

(iv) Which of the following is a method of ex-situ conservation?

• (a) National Park
• (b) Wildlife Sanctuary
• (c) Sacred Grove
• (d) Botanical Garden

(v) The enzyme used to join fragments of DNA is:

• (a) DNA polymerase
• (b) DNA ligase
• (c) Helicase
• (d) RNA polymerase

(vi) What is the full form of MALT?

(vii) Name the type of pollination that brings genetically different types of pollen grains to the stigma.

(viii) A man with blood group A marries a woman with blood group B. Their son has blood group O. What are the genotypes of the parents?

(ix) Give one example of a microbe used in the production of a beverage.

(x) What is the significance of the presence of a tail in human sperm?

(xi) Assertion: The genetic code is degenerate. Reason: Most amino acids are coded by more than one codon.

• (a) Both Assertion and Reason are true and Reason is the correct explanation for Assertion.
• (b) Both Assertion and Reason are true but Reason is not the correct explanation for Assertion.
• (c) Assertion is true and Reason is false.
• (d) Both Assertion and Reason are false.

(xii) Assertion: Use of condoms is a reliable method of contraception. Reason: Condoms prevent the entry of semen into the female reproductive tract.

• (a) Both Assertion and Reason are true and Reason is the correct explanation for Assertion.
• (b) Both Assertion and Reason are true but Reason is not the correct explanation for Assertion.
• (c) Assertion is true and Reason is false.
• (d) Both Assertion and Reason are false.

(xiii) Why is the pyramid of energy always upright?

(xiv) Name the scientist who proposed the theory of inheritance of acquired characters.

(xv) What is the function of the scrotum?

(xvi) A DNA segment has 300 guanine and 200 adenine bases. What is the total number of nucleotides in this segment?

(xvii) What is the term for the inactive pro-toxin produced by Bacillus thuringiensis?

(xviii) Differentiate between autogamy and geitonogamy.

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Section B – 14 MARKS

Question 2

What is meant by the term 'biopiracy'? Give an example.

Question 3

Explain the role of any two types of lymphocytes in the human immune system.

Question 4

Draw a labelled diagram of a mature embryo sac of a flowering plant.

Question 5

What are the main goals of the Human Genome Project?

Question 6

Differentiate between homologous and analogous organs with one example of each.

Question 7

Why is it important to conserve biodiversity? Give two reasons.

Question 8

What is parthenocarpy? Give an example of a fruit that is parthenocarpic.

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Section C – 21 MARKS

Question 9

Describe the process of spermatogenesis in humans with the help of a schematic diagram.

Question 10

Explain the mechanism of sex determination in humans.

Question 11

What is recombinant DNA technology? Describe the steps involved in the formation of recombinant DNA.

Question 12

Explain the concept of ecological succession. Differentiate between primary and secondary succession.

Question 13

Describe the structure of a typical antibody molecule with a well-labelled diagram.

Question 14

What are the different levels of biodiversity? Explain each level with an example.

Question 15

Explain the lac operon model of gene regulation in E. coli.

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Section D – 15 MARKS

Question 16

(a) Describe the process of double fertilization in flowering plants. (b) What is the fate of the primary endosperm nucleus after fertilization? (c) Give two advantages of double fertilization.

OR

(a) Describe the structure and function of the human male reproductive system. (b) Name the hormones that regulate the male reproductive system.

Question 17

(a) What is a pedigree analysis? (b) Draw a pedigree chart for a family showing the inheritance of an autosomal recessive trait. (c) How is pedigree analysis useful in genetic counselling?

OR

(a) Describe the experiment conducted by Hershey and Chase to prove that DNA is the genetic material. (b) What was the conclusion of their experiment?

Question 18

(a) What is AIDS? Name the causative agent. (b) Describe the modes of transmission of AIDS. (c) What are the preventive measures for AIDS?

OR

(a) What is cancer? (b) Differentiate between benign and malignant tumors. (c) Describe the various methods of cancer detection and diagnosis.

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Answer Key

Section A

1. (i) (a) Wuchereria bancrofti
2. (ii) (a) 0%
3. (iii) (a) Ovary
4. (iv) (d) Botanical Garden
5. (v) (b) DNA ligase
6. (vi) Mucosal Associated Lymphoid Tissue
7. (vii) Xenogamy
8. (viii) Father: I^Ai, Mother: I^Bi
9. (ix) Saccharomyces cerevisiae (Yeast)
10. (x) The tail facilitates the movement of the sperm towards the egg.
11. (xi) (a) Both Assertion and Reason are true and Reason is the correct explanation for Assertion.
12. (xii) (a) Both Assertion and Reason are true and Reason is the correct explanation for Assertion.
13. (xiii) The pyramid of energy is always upright because there is a progressive decrease in energy at successive trophic levels.
14. (xiv) Jean-Baptiste Lamarck
15. (xv) The scrotum provides the optimal temperature for spermatogenesis.
16. (xvi) 1000 nucleotides (G=300, C=300, A=200, T=200)
17. (xvii) Bt toxin
18. (xviii) Autogamy is the transfer of pollen from the anther to the stigma of the same flower. Geitonogamy is the transfer of pollen from the anther of one flower to the stigma of another flower of the same plant.

Section B

2. Biopiracy: The use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned without compensatory payment. Example: The patenting of neem and turmeric by foreign companies.
3. Lymphocytes:
   • B-lymphocytes: Produce antibodies to fight pathogens.
   • T-lymphocytes: Help B-lymphocytes to produce antibodies, and also directly kill infected cells.
4. (Diagram of a mature embryo sac should be drawn and labelled with the egg cell, synergids, polar nuclei, and antipodal cells.)
5. Goals of HGP:
   • Identify all the approximately 20,000-25,000 genes in human DNA.
   • Determine the sequences of the 3 billion chemical base pairs that make up human DNA.
6. Homologous organs: Organs with similar structure but different functions (e.g., forelimbs of whales, bats, cheetahs, and humans). Analogous organs: Organs with different structures but similar functions (e.g., wings of a butterfly and a bird).
7. Importance of biodiversity:
   • Ecological balance: Every species has a role to play in the ecosystem.
   • Economic benefits: Biodiversity provides us with food, medicine, and other resources.
8. Parthenocarpy: The development of fruit without fertilization. Example: Banana.

Section C

9. (Description of spermatogenesis with a diagram showing the stages from spermatogonium to spermatozoa.)
10. (Explanation of the XX-XY system of sex determination in humans.)
11. (Definition of recombinant DNA technology and a description of the steps: isolation of DNA, cutting with restriction enzymes, joining with ligase, and insertion into a host.)
12. (Definition of ecological succession, and the differences between primary and secondary succession.)
13. (Diagram of an antibody molecule showing the four polypeptide chains, antigen-binding sites, and disulfide bonds.)
14. (Explanation of genetic diversity, species diversity, and ecological diversity with examples.)
15. (Explanation of the lac operon model with the roles of the regulator gene, promoter, operator, and structural genes.)

Section D

16. (a) Description of the fusion of one male gamete with the egg cell and the other with the polar nuclei. (b) The primary endosperm nucleus develops into the endosperm. (c) Provides nourishment to the developing embryo and is a unique feature of angiosperms. OR (a) Description of the human male reproductive system with a diagram. (b) GnRH, LH, FSH, and testosterone.
17. (a) A pedigree analysis is the study of the inheritance of genetic traits in several generations of a family. (b) A pedigree chart showing the inheritance of an autosomal recessive trait. (c) It helps in predicting the risk of genetic disorders in future generations. OR (a) Description of the Hershey-Chase experiment using bacteriophages. (b) The experiment proved that DNA, not protein, is the genetic material.
18. (a) AIDS (Acquired Immuno Deficiency Syndrome) is caused by the Human Immunodeficiency Virus (HIV). (b) Modes of transmission include sexual contact, blood transfusions, sharing of needles, and from mother to child. (c) Preventive measures include safe sex, avoiding drug abuse, and screening of blood. OR (a) Cancer is the uncontrolled growth and division of cells. (b) Benign tumors are non-cancerous and do not spread, while malignant tumors are cancerous and can spread to other parts of the body. (c) Methods of cancer detection include biopsy, imaging techniques (CT, MRI), and blood tests.