Systematics

Phylogenetic trees of species and higher taxa are used to study the evolution of traits (e.g., anatomical or molecular characteristics) and the distribution of organisms (biogeography).

Biochemical systematics classifies and identifies animals based on the analysis of the material that makes up the living part of a cell—such as the nucleus, organelles, and cytoplasm.

Experimental systematics identifies and classifies animals based on the evolutionary units that comprise a species, as well as their importance in evolution itself.

This is a field with a long history that in recent years has experienced a notable renaissance, principally with respect to theoretical content.

Systematics uses taxonomy as a primary tool in understanding, as nothing about an organism's relationships with other living things can be understood without it first being properly studied and described in sufficient detail to identify and classify it correctly.

From the late-20th century onwards, it was superseded by cladistics, which rejects plesiomorphies in attempting to resolve the phylogeny of Earth's various organisms through time.

Today's[update] systematists generally make extensive use of molecular biology and of computer programs to study organisms.