(Solved) Phylogenetic Trees

CooperS

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11 years ago Edited: 11 years ago, CooperS

Hi, in the picture below, my teacher claims that ancestor B is more closely related to C and D than A in both trees. I see how that is true in the second tree, but isn't B equally related to A and C and D in the first tree? Neutral Face

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Quote from: CooperS (11 years ago)

Hi, in the picture below, my teacher claims that ancestor B is more closely related to C and D than A...

Sorry, that should be "descendant," not "ancestor."

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ehd123

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CooperS Author

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11 years ago

Quote from: ehd123 (11 years ago)

I do not think it is a matter of equal relatedness. In phylogenetic trees, everything is related. It is a matter of who's sequence is more similar to who.. From the tree, you can see that A is the "ancestor" of B, C, and D. They are all descendants of A, but looking at the segment length between them, it is clear that C and D resemble B much more. This goes by the reasoning that the length of the diversion with respect to the segment is close to B's segment in both C and D, indicating that there are fewer differences in the sequence with each decrease in segment length, hence less variation, and more relatedness.
Hope this helps =)

So if we just look at the difference between A -> B and B -> C, you are saying that B resembles C more than A, because the length from C->node->node->B is less than the length from A->node->node->B? Basically, are you saying that in my picture below, C is more closely related to B than A, because the green arrow has less length than the red arrow?

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ehd123

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11 years ago

You got that right! But a small comment on the B and C and A, we cannot say that B resembles C more that A, after all B IS a descendant of A. All of them are, but if we are to compare the "sequential" differences between them, then yes, C would be much more related to B than A. You need to be careful with how to state your statement.
Remember that the segments represent the time it took for the descent with modification to take place, which is almost the same here, and the horizontal segment from the vertical segment, representing the "amount" of variation" between the 'ancestor' and the descendent.

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CooperS Author

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11 years ago

Quote from: ehd123 (11 years ago)

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