Section D (Q Nos. 22 – 24 are of 3 marks each)
Question 22: Study the schematic representation given above and answer the following questions:
(a) Identify A in it.
(b) Identify D in it.
(c) When the population density at time t is N as shown above, write the population density at time t + 1 in the form of an equation using appropriate symbols.
Answer:
a) A = Natality / Immigration.
b) D = Emigration / Mortality .
c) N (t+1) = Nt +[(B+I) – (D+E)].
Question 23: (a) Identify steps A and B in a cycle of Polymerase Chain Reaction given below.
(b) State the specific characteristic feature of the enzyme in carrying step B.
Answer:
a) A= Annealing; B=Extension.
b) Thermostable (DNA Polymerase) / remains active at high temperature.
Question 24: Study the diagrammatic representation of S.L. Miller’s experiment given below and answer the questions that follow:
(a) How did S.L. Miller create the conditions which existed before the origin of any life on Earth?
(b) Name the organic compound formed and collected at the end of his experiment.
(c) Mention the kind of evolution his experiment supports.
Answer:
(a) (Conditions existed before the origin of life – High temperature, volcanic storms, reducing atmosphere containing CH4, NH3, etc.). Conditions were created by electric discharge (high temperature) in a closed flask containing CH4, NH3, H2, water vapours.
b) Amino acids.
c) Chemical evolution.
Previous Year Question Paper for CBSE Class 12 Biology – 2020
CBSE Class 12 Biology Previous Year Question Paper helps you to understand the level of questions asked in the previous exams, along with the changes in pattern. Practicing the previous year’s question paper for CBSE Class 12 Biology enhances time-management skills while appearing in the board examination. It makes you understand the importance of different topics that have been asked previously.
Previous year’s CBSE Class 12 Biology Question Papers will boost your confidence level to appear in the examination with proper knowledge of different topics that are going to be asked. It enhances the understanding of the topic and acts as a checkpoint to see the level of preparation that you have done. CBSE Class 12 Biology Question Papers 2020 is available here.