Question

in the figure, the letters a-g represent individual species that all descended from a common ancestor.

which of the following conclusions regarding the phylogeny of these organisms can be made from this tree?

a is more closely related to d than it is to c
b is more closely related to g than it is to a
d is more closely related to e than it is to g
g is more closely related to a than it is to f

Explanation:

Analyze the phylogenetic tree structure

Using the Phylogenetic Trees knowledge point
The tree splits into two major clades: one containing \(A\), \(B\), and \(C\), and the other containing \(D\), \(E\), \(F\), and \(G\). Within the second clade, \(D\) and \(E\) share a highly immediate common ancestor, while \(F\) and \(G\) share another.

Evaluate evolutionary relationships

Using the Evolutionary Relationships knowledge point

• \(A\) and \(C\) share a common ancestor within their clade, whereas \(A\) and \(D\) only connect at the root. Thus, \(A\) is more closely related to \(C\) than to \(D\).
• \(B\) shares a more recent common ancestor with \(A\) than with \(G\).
• \(D\) and \(E\) share a very recent common ancestor, whereas \(D\) and \(G\) share a much older common ancestor at the base of the \(D\)-\(G\) clade. Thus, \(D\) is more closely related to \(E\) than to \(G\).
• \(G\) shares a recent common ancestor with \(F\), but only connects to \(A\) at the root. Thus, \(G\) is more closely related to \(F\) than to \(A\).

Determine the correct option

Using the Phylogenetic Trees knowledge point
The statement "D is more closely related to E than it is to G" is correct because the most recent common ancestor of \(D\) and \(E\) is younger (more recent) than the most recent common ancestor of \(D\) and \(G\).

Answer:

• (A) A is more closely related to D than it is to C
• (B) B is more closely related to G than it is to A
• (C) D is more closely related to E than it is to G (Correct answer)
• (D) G is more closely related to A than it is to F