7.6 Evidence of Evolution

Lines of evidence

Evolution is supported by many independent lines of evidence: the fossil record (a timeline of past life), comparative anatomy, embryology (similar early development), molecular biology (DNA and protein similarities), and biogeography (where species live).

Homologous vs. analogous

Homologous structures share a common ancestral origin even if their functions differ (a whale flipper and a human arm). Analogous structures have similar functions but different origins, arising by convergent evolution (bird and insect wings). Vestigial structures are reduced remnants with little or no current function.

Key terms

Homologous structures

Structures with common ancestry, even if functions differ (whale flipper, human arm).

Analogous structures

Similar-function structures from convergent evolution, not common ancestry (bird vs. insect wing).

Vestigial structures

Reduced remnants with little or no current function.

Fossil record

The preserved remains and traces of organisms, documenting change over time.

Molecular evidence

DNA and protein similarities that reveal evolutionary relationships.

Try an AP-style question

The forelimbs of humans, bats, whales, and cats have the same bones arranged differently. What best explains this?

1. They are vestigial structures with no function
2. They are homologous structures inherited from a common ancestor
3. They evolved because all four animals live in the same habitat
4. They are analogous structures that evolved separately