To apply parsimony to constructing a phylogenetic tree,
A choose the tree that assumes all evolutionary changes are equally probable.
B choose the tree in which the branch points are based on as many shared derived characters as possible.
C choose the tree with the fewest branch points.
D base phylogenetic trees only on the fossil record, as this provides the simplest explanation for evolution.
E choose the tree that represents the fewest evolutionary changes, in either DNA sequences or morphology.
The Correct Answer and Explanation is :
The correct answer is E: choose the tree that represents the fewest evolutionary changes, in either DNA sequences or morphology.
Explanation:
Parsimony, in the context of constructing phylogenetic trees, is a principle based on the idea of minimizing the number of evolutionary changes (or steps) required to explain the observed data. The assumption is that, all else being equal, the simplest explanation, which involves the fewest changes, is the most likely.
When constructing phylogenetic trees, we often compare different potential evolutionary pathways to determine the tree that best represents the relationships among species or taxa. The principle of parsimony helps in selecting the tree that requires the fewest changes in character states (such as DNA mutations or morphological traits) across the tree’s branches.
For example, if you have a set of species with certain traits (such as specific nucleotides in a gene sequence), the parsimony approach would favor the tree that minimizes the number of changes in those traits as you trace the evolutionary path from the common ancestor to the species in question. This is particularly important when the phylogenetic analysis involves molecular data, such as DNA or protein sequences, where each mutation or change is a step in the evolutionary process.
Let’s break down the other options:
- A (Choosing a tree where all evolutionary changes are equally probable) is incorrect because it disregards the principle of minimizing changes.
- B (Choosing a tree based on shared derived characters) is a sound strategy for inferring relationships but doesn’t specifically emphasize minimizing evolutionary changes.
- C (Choosing a tree with the fewest branch points) is irrelevant since branch points (nodes) don’t directly reflect the number of evolutionary changes.
- D (Basing trees only on the fossil record) is overly restrictive and doesn’t always reflect the most accurate phylogenetic relationships, as molecular data often provides more detailed and less ambiguous insights.
Thus, parsimony directly involves minimizing the total number of evolutionary steps, and this is why E is the correct choice.