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I'm confused with the illustrations of allopatric speciation. Here are two diagrams- Fig 1 Fig 2

Which one of them is correct and why?

According to wikipedia the second figure is correct but I'd like to know why is it so, or why can't be the first one be right?

All I know about allopatric speciation is that it is a process of formation of new species from existing species in the following way-

  1. A large ancestral population is firstly spatially divided into two subpopulation
  2. Evolutionary forces act on the subpopulations
  3. Eventually with large span of time reproductive isolation develops between them and finally lead to new species

According to my concept fig 1 is correct but I find the other diagram all over the internet.

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closed as off-topic by MattDMo, kmm, fileunderwater, rg255, AliceD Apr 23 '16 at 20:51

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Homework questions are off-topic on Biology unless you have shown your attempt at an answer. For more information see our homework policy." – MattDMo, kmm, fileunderwater, rg255, AliceD
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 4
    $\begingroup$ For the millionth time, when asking homework questions, you must show your attempt at an answer. "Because I read it on Wikipedia" is not an attempt at answering. With all of the low-quality questions you ask, you are at risk of being question-banned on this site. PLEASE improve your questions. $\endgroup$ – MattDMo Apr 23 '16 at 17:28
  • $\begingroup$ @MattDMo I've added some information. I didn't write this before because it was not related to my question directly. $\endgroup$ – Tyto alba Apr 24 '16 at 11:35
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Both are correct. From Wikipedia, the causes of genetic change within each now-separate population are: (a) they become subjected to different selective pressures, (b) they independently undergo genetic drift, and (c) different mutations arise in the gene pools of the populations.

It is possible that factors a, b, and c cause the emergence of 2 new species -- or just 1 (which is possible considering that the original species probably is well-suited to its current habitat).

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