Study Help

Answering questions about Allopatric speciation

by Gary Mann

Gary Mann is the Head of Life Sciences at CBC Parklands.

Remember this is the process of how we think that existing species are able to give rise to new species. You need to be able to name and explain two of these, namely allopatrick and sympatrick speciation.

Allopatric speciation occurs when a population has become geographically divided/split and separated, each group then being subjected to different natural selection pressures, and finally establishing reproductive isolating mechanisms.

How would you answer a question about allopatrick speciation using an example?

Look at the example below to see how to answer this question so that you maximise the number of marks you will achieve.


  • Explain the process of allopatrick speciation using Darwin’s finches as an example.


  • There is a great deal of variation within a population (e.g. amongst the finches there are different shapes of beaks)
  • (On each island the finches lived under) different environmental conditions/ had different sources of food.
  • The population (finches) underwent natural selection.
  • Only those (finches) that were better suited to obtain the type of food available survived and were able to reproduce.
  • Continued natural selection on each island over many generations resulted in each island having species that were {genotypically and phenotypically} very different from each other.
  • These differences prevented them from interbreeding leading to the formation of new species.
  • This is termed allopatric speciation or adaptive radiation.

If you are asked to explain this process using any other appropriate example, then you simply substitute the words in (brackets) above with the name of the stated example and the situation in which it occurs.

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