Question

The idea of common descent came to Darwin by his observations on

• A. Geographic distribution of species
• B. Comparative embryology
• C. Phylogenetic structures
• D. Blood groups of animals

Answer 1

Answer: (A)

Geographic distribution of species

Darwin got idea of common descent of species from the geographical distribution of species. Particularly finches from Galapagos island. The Galápagos finches are seen as a classic example of adaptive radiation, the rapid evolution of ecologically different species from a common ancestor. Comparisons of anatomical features of the Galápagos finches show they are indeed more closely related to each other than to any other species. This means they form a monophyletic group, a group of organisms all descended from one ancestral species.

If one or more populations are isolated from the rest of a species over many generations (and members of each isolated population breed only with one another), each population may become distinct from the original species. Each isolated population may face a unique set of environmental conditions that the population will need to adapt to. If so, each population may evolve differently.

So, the correct option is 'Geographic distribution of species'.