Question

What is meant by biogeography? Discuss the biogeographic evidence in support of organic evolution.

Answer 1

Hint: The study of life forms on earth is known as evolutionary biology. Evolution is the sequence of regular or continuous changes which take place in the primitive organisms over millions of years in which new species are produced.
Organic evolution is the change in the hereditary makeup of species in a population as a result of responding to ecological changes.

Complete answer:
The study of distribution of various organisms in different parts of the earth is called biogeography. By this we can reconstruct their evolutionary histories.
Speciation is the procedure in which new species develop from the existing species. In most cases, new species form when the population of the same species splits into two separate groups which then get isolated from each other geographically. This leads to their reproductive isolation due to which no genes are exchanged between them.
Biogeographical Evidences-
The earth has been divided in 6 regions on the basis of distribution and range of plants and animals.
Closely similar species exist at widely separated places without any representatives called discontinuous distribution. Example- alligators, lung fishes, camels, etc.
Parts which are separated from the mainland have unique flora and fauna are restricted distribution. Example- pouched mammals and egg-laying occur only in Australia.
Those organs which have the same basic structure but different functions are called homologous organs that show adaptive radiation. Example- Darwin’s finches and marsupials of Australia.
Two or more groups of unrelated animals come to resemble each other for a similar mode of life is called convergent evolution. Example-Australian marsupials, placental mammals.

Note-
Evolution has four principles- variation, inheritance, selection and time. The more features two species have in common, the more closely they will be related.
Some of the important sources which provide evidence for evolution are- homologous and analogous organs, and fossils.