Homologous Structures

Of separate lineages, comparable body parts that show underlying similarity even when they may differ in size, shape, or function; outcome of morphological divergence from a shared ancestor.

Gondwana

Paleozoic supercontinent; with other land masses, it formed Pangea.

Geologic Time Scale

Time scale for the Earth's history with major subdivisions corresponding to mass extinctions. Now radiometrically dated.