- A keystone species plays a critical role in maintaining the structure of an ecosystem. Their removal can cause major disruptions.
- Removal of a keystone species often leads to a collapse of population balance and possibly extinction of species that depend on it, so (C) is correct.
- (A) is incorrect because biodiversity usually decreases, not increases, after keystone species removal.
- (B) is incorrect; food webs become destabilized without keystone species.
- (D) is incorrect; significant changes usually occur in the ecosystem.
Answer: \(\boxed{\text{C}}\)
Study the figure given below and answer the questions that follow.
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.