Name: Types of Speciation
Uploaded: 2019-07-19
Duration: 6 min 35 s
Description: There are five types of speciation: allopatric, peripatric, parapatric, sympatric and artificial. Wanna learn more? Watch this informative video.

Question

What is meant by bio-geography? Discuss the biogeographic evidence in support of organic evolution.

Accepted Answer

Biogeography is the study of the distribution of animals and plants on this Earth. The evidence of evolution based on biogeography is called biogeographical evidence. These can be explained under the following headings.

Biogeographical Realms. The earth has been divided into six major biogeographic regions, called realms on the basis of the distribution of animals and plants.

These regions are :

(i) Palaearctic realm. It includes Europe, North of the Himalayas, China, the Sahara desert of Africa, Siberia, and a major part of Asia.

(ii) Oriental realm — It includes India, Malaysia, Philippines, Indonesia, Sri Lanka, Myanmar (Burma).

(iii) Australian realm. It includes Australia, New Zealand, New Guinea.

(iv) Ethiopian realm. It includes Africa, Arabia, and Madagascar.

(v) Nearctic realm. It covers Canada, the United States of America, and Mexico.

(vi) Neotropical realm. It includes the area of Central and South America and the Island of West-Indies.

Discontinuous Distribution of closely related species-Sometimes closely similar species exit at widely separated places without any representative in the intervening territory. This is called discontinuous distribution. E.g. Alligators occur only in the south-eastern United States and eastern China, Lung Fishes are only found in South America, Africa, and Australia. Elephants are found in Africa and India and not in places with an identical climate like Brazil.

Restricted Distribution. The parts separated from the mainland have unique fauna and flora. For example, Australia has (i) egg-laying and (ii) pouched mammals that occur only in Australia.

Adaptive Radiation — The development of different functional structures from a common ancestral form is called adaptive radiation. E.g. Darwin’s Finches of the Galapagos Islands had common ancestors but now have different types of modified beaks according to their food habits and adaptive radiation gave rise to a variety of marsupials (pouched mammals) in Australia.

Convergent Evolution-Development of similar adaptive functional structures in unrelated groups of organisms is called adaptive convergence or convergent evolution. Analogous organs are developed for convergent evolution E.g. Wings of insect, bird, and bat, Australian marsupials, and placental mammals show convergent evolution.

What is meant by bio-geography? Discuss the biogeographic evidence in support of organic evolution.

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