5.4 Cladistics

Cladistics

A method of classifying living organisms based on the construction and analysis of cladograms, which show the evolutionary relationships between species based on shared ancestry and characteristics.

Clade

A group of organisms that consists of a common ancestor and all its lineal descendants, representing a single "branch" on the "tree of life."

Cladogram

A tree diagram used to show the evolutionary relationships among various biological species based on similarities and differences in their physical or genetic characteristics.

Node

A point on a cladogram where a single ancestral lineage breaks into two or more descendant lineages

Root

The point on a cladogram prior to any divergence where all the organisms share certain characteristics.

Analogous Traits

Characteristics that have similar functions but have evolved separately from different ancestral features, resulting from convergent evolution.

Homologous Traits

Characteristics shared by organisms due to shared ancestry, which may have different functions due to divergent evolution.

Convergent Evolution

The independent evolution of similar features in different species which did not develop from a common ancestor, leading to analogous structures.

Divergent Evolution

The process whereby groups from the same common ancestor evolve and accumulate differences, resulting in the formation of new species.

Molecular Clock

A technique that uses the mutation rate of genes to calculate how much time has passed since two or more life forms diverged from a common ancestor.

Phylogenetic Tree

A diagram that represents evolutionary relationships among organisms based on genetic similarities and differences and shows the time periods between speciation events. Uses the molecular clock technique to calculate this.

Morphology

The study of the form and structure of organisms and their specific structural features.

Common ancestor

An ancestral species from which later species diverged and evolved.