Evolution of animals

accumulation of differences between closely related species populations, leading to speciation

general appearance of an animal resulting from the reflection or emission of light from its surfaces

forelimb evolved for movement through water

animal that uses aerial locomotion

natural history of mating systems in which species pair bond to raise offspring

The Urmetazoan is the hypothetical last common ancestor of all animals. The name derives from metazoa, an old biological term for animals. It is universally accepted to have been a multicellular heterotroph — with the novelties of a germline and oogamy, an extracellular matrix (ECM) and basement membrane, cell-cell and cell-ECM adhesions and signaling pathways, collagen IV and fibrillar collagen, different cell types (as well as expanded gene and protein families), spatial regulation and a complex developmental plan, and relegated unicellular stages.