Younger fossils are often morphologically different from older fossils in a lineage. How do paleontologists think the morphological transition happened?
A) The younger fossils are a species that underwent anagenesis, gradually evolving a new morphology.
B) The younger fossils are a new species that branched off the older one, rapidly evolving a new morphology.
C) The younger fossils are likely a new species from a different lineage that migrated to the area.
D) a and b
E) none of the above

Question

Quizplus · Accepted Answer

Both anagenesis (A), where a species evolves gradually over time into a new form, and cladogenesis (B), where a new species branches off from an ancestor and evolves rapidly, are recognized mechanisms by which morphological transitions can occur in the fossil record.

Younger Fossils Are Often Morphologically Different from Older Fossils in a Lineage