Homologous structures — Science definition
Body parts that share the same underlying anatomical plan because they were inherited from a common ancestor, even when they now perform different functions — such as the forelimbs of humans, whales, and bats.
Where it is taught
- Evidence for Evolution — Evolution, Ancestry & Biodiversity, Life Science: Biology, Grade 10
In use
These homologous structures only make sense if all three species inherited that limb plan from a shared ancestor and then modified it.
Evidence for Evolution
Questions using homologous structures
Problem 1
- a total absence of any evolutionary relationship
- descent from a common ancestor
- convergent evolution from unrelated ancestors
- traits acquired during life
Answer and explanation
descent from a common ancestor
Homologous structures share an underlying anatomical plan because the species inherited it from a common ancestor, even though the structures now serve different functions.
Problem 2
- perform the same function in unrelated species
- share a common underlying structure and ancestry, whatever their current function
- are always vestigial
- have identical DNA
Answer and explanation
share a common underlying structure and ancestry, whatever their current function
Homologous structures share an inherited underlying plan — the limb bones of mammals, for instance — even when their functions differ.