05 Origin and Evolution of life - part 12 - Speciation

05 Origin and Evolution of life - part 12 - Speciation


Speciation : 
  • The process of formation of a new species from the per-existing species is called speciation. 
  • Species is a group of similar organisms that can interbreed and produce a fertile offspring in nature. 
  • New species are formed by the following modes. 
a. Intraspecific Speciation : 
i. Allopatric speciation : 
  • Formation of a new species due to separation of a segment of population from the original population by distanced or a geographical barrier cutting across the species range.
  •  e.g. creeping glaciers, development of mountains. 
  • Migration of individual also causes allopatric speciation. The mode of evolution here is called adaptive radiation
  • e.g. 14 different species of finches in Galapagos islands and several marsupial species in the Australian continent. 
ii. Sympatric speciation: 
  • Formation of species within single population without geographical isolation. These are formed due to reproductive isolation. 
  • e.g. Cichlid fishes in Lake Victoria. 
  • Mutations are helpful in sympatric speciation. 
b. Interspecific Speciation : 
Hybridisation :
  • Two different species on crossing may give rise to a new species. 
  • e.g. Mule is a hybrid produced by interbreeding between a male donkey and a female horse. 
  • Hinny is offspring of male horse and female donkey.

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