Question

Highly conserved proteins such as Haemoglobin and Cytochrome-C provide the best biochemical evidence to trace evolutionary relationships between different groups. Cytochrome-C is formed of 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	100	125 mya
Human/Cow	75	120 mya
Human/Rodent	60	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)
(i) Define convergent evolution.
OR
(ii) Define divergent evolution.

Hint:

Greater genetic difference in conserved genes like Cytochrome-C usually indicates a longer evolutionary separation between species.

Answer 1

(a) Cytochrome-C Evolution Data

(i) The correct choice is:

Options	Time of separation of two groups during evolution	Number of nucleotide substitutions
(i)	Lesser	Greater
(ii)	Greater	Lesser
(iii)	Greater	Greater

(b) Inferences about Evolution

(i) Type of Evolution for the Given Groups:

The evolution between the groups can be categorized as divergent evolution, particularly when comparing humans and kangaroos or humans and rodents.

This is because these groups share a common ancestor but have adapted to different environmental conditions, leading to the evolution of distinct species with different traits.

(ii) Definition of Convergent Evolution:

Convergent Evolution refers to the process where organisms from different evolutionary backgrounds develop similar traits or characteristics, typically due to similar environmental pressures or ecological niches. An example of this is the development of wings in both birds and bats, which evolved independently from different ancestral lineages.

OR

(ii) Definition of Divergent Evolution:

Divergent Evolution occurs when two or more related species become more dissimilar over time, typically due to different environmental pressures. This is observed in the evolution of different species from a common ancestor, such as the evolution of different mammalian species from early ancestors into distinct species like humans, dogs, and whales.