CBSE 2025 · Region 5 · Set 1 · Q29 · 4 marks
Highly conserved proteins such as Haemoglobin and Cytochrome-C provide the best biochemical evidences to trace evolutionary relationships between different groups. Cytochrome-C is formed of $\displaystyle 104$ amino acids. Cytochrome-C is the respiratory pigment present in all eukaryotic cells. It has evolved at a constant rate during evolution. In chimpanzees and humans, Cytochrome-C genes are identical. The given data shows the evolution of the Cytochrome-C gene in different mammals from kangaroos, cows, rodents to humans : Groups Nucleotide substitution in the gene of Cytochrome-C Millions of years ago Human/Kangaroo $\displaystyle 100$ $\displaystyle 125$ mya Human/Cow $\displaystyle 75$ $\displaystyle 120$ mya Human/Rodent $\displaystyle 60$ $\displaystyle 75$ mya
(a)Select the correct option for the time of separation of two groups and the number of nucleotide substitutions in the gene of Cytochrome-C : Options Time of separation of two groups during evolution Number of nucleotide substitutions (i) Lesser Greater (ii) Greater Lesser (iii) Greater Greater
(b)What do you infer about the type of evolution (convergent or divergent) for the given pair of groups and why ?(i)Human and Kangaroo(ii)Human and Rodent(c)Define convergent evolution.(ii)Define divergent evolution.
Highly conserved proteins such as Haemoglobin and Cytochrome-C provide the best biochemical evidences to trace evolutionary relationships between different groups. Cytochrome-C is formed of $\displaystyle 104$ amino acids. Cytochrome-C is the respiratory pigment present in all eukaryotic cells. It has evolved at a constant rate during evolution. In chimpanzees and humans, Cytochrome-C genes are identical. The given data shows the evolution of the Cytochrome-C gene in different mammals from kangaroos, cows, rodents to humans :
| Groups | Nucleotide substitution in the gene of Cytochrome-C | Millions of years ago |
| Human/Kangaroo | $\displaystyle 100$ | $\displaystyle 125$ mya |
| Human/Cow | $\displaystyle 75$ | $\displaystyle 120$ mya |
| Human/Rodent | $\displaystyle 60$ | $\displaystyle 75$ mya |
(a)
Select the correct option for the time of separation of two groups and the number of nucleotide substitutions in the gene of Cytochrome-C :
| Options | Time of separation of two groups during evolution | Number of nucleotide substitutions |
| (i) | Lesser | Greater |
| (ii) | Greater | Lesser |
| (iii) | Greater | Greater |
(b)
What do you infer about the type of evolution (convergent or divergent) for the given pair of groups and why ?
(i)
Human and Kangaroo
(ii)
Human and Rodent
(c)
Define convergent evolution.
(ii)
Define divergent evolution.
Marking-scheme solution
(iii)
Greater, Greater
(i)
Divergent evolution
(ii)
Divergent evolution
both indicates common ancestry as in both cases cytochrome C is the respiratory pigment.
(c)
Convergent evolution: Different structures evolving for the same function and hence
having similarity.
(ii)
Divergent evolution: Same structure developed along different directions due to
adaptations to different needs.
EvolutionWhat are the Evidences for Evolution?Analysecase_studymedium
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CBSE Class 12 Biology past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.