Board Paper of Class 12 2020 Biology - Solutions
This paper comprises TWO PARTS – Part A and Part B.
Answer all questions.
Part A consists of one question of 20 marks having six subparts.
Part B consists of Sections A, B and C.
Section A consists of seven questions of two marks each.
Section B consists of seven questions of three marks each, and Section C consists of three questions of five marks each.
Internal choices have been provided in two questions in Section A, two questions in Section B and in all three questions of Section C.
The intended marks for questions or parts of questions are given in brackets [ ].
Answer all questions.
Part A consists of one question of 20 marks having six subparts.
Part B consists of Sections A, B and C.
Section A consists of seven questions of two marks each.
Section B consists of seven questions of three marks each, and Section C consists of three questions of five marks each.
Internal choices have been provided in two questions in Section A, two questions in Section B and in all three questions of Section C.
The intended marks for questions or parts of questions are given in brackets [ ].
- Question 1
(a) Answer the following questions briefly and to the point:
(i) How many chromosomes are present in male gamete of a rat?
(ii) Why is haemophilia uncommon in females?
(iii) Name the disease-resistant variety of cowpea developed by plant breeding technique.
(iv) Define Brood parasitism.
(v) Name the vegetative propagule of Bryophyllum.
(vi) Which geological era was dominated by reptiles?
(vii) Define polygenic inheritance.(viii) What is Dobson unit?
(b) Each of the following sub-parts, (i) to (iv) has four choices. Choose the best option in each case:
(i) If 10 individuals in a laboratory population of 100 mice die during the period of one year, the death rate in this population will be:(1) 110
(2) 0·01
(3) 0·1
(4) 90
(ii) The flowers which open their petals to expose their reproductive parts to allow pollination are called:(1) Cleistogamous
(2) Geitonogamous
(3) Chasmogamous
(4) Autogamous
(iii) Which of the following is paired incorrectly:(1) Cyclosporin A - Trichoderma polysporum
(2) Streptokinase - Saccharomyces cerevisiae
(3) Swiss Cheese - Propionibacterium
(4) Penicillin - Penicillium
(iv) The pathogen which causes Syphilis:(1) Neisseria
(2) Chlamydia
(3) Treponema
(4) Papilloma virus
(c) Give one significant contribution of each of the following scientists:
(i) F. Griffith
(ii) P. Ehrlich
(d) Expand the following:
(i) IUI
(ii) ADA
(e) Define the following:
(i) Biopiracy
(ii) Aneuploidy
(f) Give a reason for each of the following:
(i) Cyanobacteria increase the productivity in paddy fields.
(ii) The shape of the pyramid of biomass in an aquatic ecosystem is inverted. VIEW SOLUTION
- Question 2
Give one significant difference between the following:
(i) Linkage and crossing over
(ii) Transition and transversion VIEW SOLUTION
- Question 3
Study the graph given below and answer the questions that follow:
(i) In the absence of predators which one of the two curves would appropriately depict the prey population? Give a reason.
(ii) Time has been shown on X-axis and there is a parallel dotted line shown above. Explain the significance of this dotted line. VIEW SOLUTION
- Question 4
What is biogas? Name any two main constituents of biogas. VIEW SOLUTION
- Question 5
Explain two characteristics of cancer cells. VIEW SOLUTION
- Question 6
(a) Draw a labelled diagram of a germinating pollen grain with at least four labellings.
OR
(b) Draw a labelled diagram of a mature human ovum with at least four labellings. VIEW SOLUTION
- Question 7
What is outbreeding? How is it useful in animal breeding? VIEW SOLUTION
- Question 8
(a) What is biomagnification? Write two effects of biomagnification.
OR
(b) Write a short note on the contribution of Ahmed Khan of Bangalore. VIEW SOLUTION