Source 1: enter image description here

Source 1 shows a map of a particular area. In this map you will find the mountain ranges 1 and 2, the species P, Q and R. Two possible pedigrees of the ancestral history of the species P, Q and R are drawn . Which mountain range was formed first (historically) and which pedigree is correct?

  • $\begingroup$ 1 might have formed first and I think pedigree 1 is correct. $\endgroup$
    – biogirl
    Nov 5, 2013 at 16:14

1 Answer 1


If mountain range 1 was formed first, pedigree 1 is correct.

If mountain range 2 was formed first, none of the two pedigree seem correct.

If mountain range 1 was formed first you would first have the split of the initial population into population P and the population Q+R. Then, the formation of mountain range 2 split the population Q+R into Q and R. Therefore, Q and R are more closely related than they both are to P. Therefore Pedigree 1 is correct.

You can apply the same kind of reasoning by guessing that mountain range 2 was formed first and you will realize that you would expect a pedigree different than Pedigree 1 and Pedigree 2. If mountain range 2 appeared first then, the correct Pedigree would display the population/species/lineages P and Q more closely related to each other than they both are to R.

  • $\begingroup$ Could you elaborate on why you think so? $\endgroup$
    – user4847
    Nov 5, 2013 at 16:16
  • $\begingroup$ @user4847 Update! Does it make sense to you? $\endgroup$
    – Remi.b
    Nov 5, 2013 at 16:29
  • $\begingroup$ I approve it.... $\endgroup$
    – user4847
    Nov 5, 2013 at 16:37

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