5.4 Cladistics

Traits or structures which are similar because of convergent evolution, not because of a shared common ancestor.

Analogous

An evolutionary branch of a cladogram that includes a single ancestor and all of the species that have evolved from it.

Clade

A classification system that places organisms into groups called clades based on common ancestry, and shared characteristics.

Cladistics

A branching diagram showing the relationships between a number of species based on ancestry (cladistics).

Cladogram (phylogenetic tree)

Where species from different ancestry show similar characteristics because they are subject to similar selection pressures. The feature has evolved separately in each species.

Convergent evolution

Where an ancestral species evolves into a number of distinct species due to different selection pressures acting on isolated populations of the species.

Divergent evolution

A family of angiosperm plants which has been reclassified using new evidence from molecular genetics

Figwort (Scrophularia spp.)

Traits found in different species that are morphologically similar because they have been inherited from a common ancestor.

E.g. A whale fin and a human arm.

Homologous trait

Model that uses the number of differences in DNA or amino acid sequences to deduce how long two species have been evolving independently.

Molecular clock

An animal order in the mammal class, including lemurs, monkeys, apes and human beings.

Primates

Changes in the order of DNA bases or amino acids in the same genes or proteins between species. The more differences there are the longer the time since the species diverged from a common ancestor

Sequence differences