Which describes a polyphyletic group?

Which describes a polyphyletic group?

• A. An ancestor and all its descendants.
• B. An ancestor and some, but not all, of its descendants.
• C. A group composed of organisms with different ancestors and no recent common ancestor.
• D. A group defined strictly by shared ancestry.

Answer: (C)

Polyphyletic groups are formed when members come from different evolutionary lineages and do not share a recent common ancestor within the group. The defining feature is that similarities among the members do not reflect a single shared ancestry; instead, those similarities are often the result of convergent or parallel evolution. That’s why a description of a group made up of organisms with different ancestors and no recent common ancestor fits best. For comparison, a group that includes an ancestor and all its descendants is a true clade, a monophyletic group. A group that includes an ancestor and only some of its descendants is paraphyletic. And a group defined strictly by shared ancestry also points to monophyly. Therefore, the option describing organisms from different lineages with no recent common ancestor best matches a polyphyletic grouping.

Polyphyletic groups are formed when members come from different evolutionary lineages and do not share a recent common ancestor within the group. The defining feature is that similarities among the members do not reflect a single shared ancestry; instead, those similarities are often the result of convergent or parallel evolution. That’s why a description of a group made up of organisms with different ancestors and no recent common ancestor fits best.

For comparison, a group that includes an ancestor and all its descendants is a true clade, a monophyletic group. A group that includes an ancestor and only some of its descendants is paraphyletic. And a group defined strictly by shared ancestry also points to monophyly. Therefore, the option describing organisms from different lineages with no recent common ancestor best matches a polyphyletic grouping.