A: Morphological Phylogeny. B: Molecular Phylogeny

question 23

Multiple Choice

A: Morphological phylogeny. B: Molecular phylogeny.
In the traditional morphological phylogeny (A) , the phylum Platyhelminthes is depicted as a sister taxon to the rest of the protostome phyla and as having diverged earlier from the lineage that led to the rest of the protostomes. In the molecular phylogeny (B) , Platyhelminthes is depicted as a lophotrochozoan phylum. What probably led to this change?

• A) Platyhelminthes ceased to be recognized as true protostomes.
• B) Similarity of genetic information has led to realization that some morphological features are evolutionarily flexible (e.g., coelom formation) and so cannot be used as a diagnostic character.
• C) All Platyhelminthes must have a well-developed lophophore as their feeding apparatus.
• D) Platyhelminthes' close genetic ties to the arthropods became clear as their Hox gene sequences were studied.

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Definitions:

Sample

A subset of individuals from a larger population, selected to represent that population in a study or experiment.

Random Assignment

A method used in experiments where participants are allocated to different groups in a way that every participant has an equal chance of being assigned to any group.

Random Sample

A method of selecting a sample from a population in which each member has an equal chance of being chosen.

External Validity

The extent to which the results of a study can be generalized to other situations and to other people.