Phylogenetic trees are hypotheses about the shared ancestor-descendent relations
ID: 91970 • Letter: P
Question
Phylogenetic trees are hypotheses about the shared ancestor-descendent relationships among taxa. For any given set of taxa, the available data is likely to suggest more than one possible tree. How do biologists decide which tree is more likely to be the correct one?
A. The tree with the fewest number of nodes (connections between branches) is likely to the the correct tree.
B. The tree with the fewest number of character state changes (transitions) is more likely to be the correct tree.
C. The question begins with a false premise. Phylogenetic trees are not hypotheses about ancestor-descendent relationship among taxa. Trees reflect that facts of evolutionary relationships as we know them. There is only one possible tree.
D. There is no way to tell from looking at just the trees which one is more likely to be correct. It is also necessary to perform at least some breading experiments; for example, reciprocal transplant experiments.
E. The tree with the fewest number of branches is most likely to be the correct tree.
Explanation / Answer
Answer is B
Biologists use a method called Maximum Parsimony to determine the correct tree. The criteron which this method is based on is that the tree with the fewest number of character state changes (transitions) is more likely to be the correct tree.