Practice: Phylogenetic Trees #1 Answer the questions about each tree below. 1. In the diagram to the right, which node represents the most recent common ancestor for organisms
and
? Node 2 represents the nost recent common oncestor 2. Which node represents the most recent common ancestor for
and
? Node 1 3. Which organism is B more closely related to, A or C? Explain. Node A 4. Which organism is B more closely related to, C or D? Explain. Both Node
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The Correct Answer and Explanation is:
Corrected Answers:
- In the diagram to the right, which node represents the most recent common ancestor for organisms B and C?
Correct Answer: Node 2 - Which node represents the most recent common ancestor for A and C?
Correct Answer: Node 1 - Which organism is B more closely related to, A or C? Explain.
Correct Answer: A.
Explanation: B is more closely related to A because they share Node 1 as a more recent common ancestor, whereas the common ancestor with C occurs at Node 2, which is further up the tree. - Which organism is B more closely related to, C or D? Explain.
Correct Answer: C.
Explanation: B is more closely related to C than D because B and C share Node 2 as a more recent common ancestor. D does not share a direct ancestor with B until Node 3, which is farther back in evolutionary time.
Explanation:
Phylogenetic trees are diagrams that depict the evolutionary relationships among various biological species based on similarities and differences in their physical and/or genetic characteristics. In a phylogenetic tree, each node represents a common ancestor from which the species diverged. The closer two organisms are on a tree and the more recent their common ancestor, the more closely related they are.
In this tree, Node 2 is the point where the lineages of organisms B and C converge, indicating that Node 2 is their most recent common ancestor. Since Nodes represent branching points of evolutionary divergence, this shows that B and C share a more recent lineage than they do with any other organism.
When considering organisms A and C, their lineages converge only at Node 1, which lies deeper in the tree than Node 2. This indicates that their most recent common ancestor lived further back in time, making them less closely related than organisms that share Node 2 or Node 3.
Between organisms B and A, Node 1 is the common ancestor, showing that they diverged earlier than B and C (which diverged at Node 2). Thus, B is more closely related to A than to C.
For the last question, between organisms C and D, Node 3 is where their lineages meet, which is higher up the tree and therefore less recent. B and C, however, share Node 2, which makes them more closely related to each other than either is to D.
Understanding these relationships helps scientists reconstruct evolutionary histories and infer traits of common ancestors.
