5.4 (Cladistics (evolution))

Analogous

trait structures which are similar because of convergent evolution.

Clade

a group comprised of an ancestral species plus all of the species that have evolved from the organism.

Cladistics

constructing a phylogenetic tree based on primitive and shared derived characteristics.

Cladograms

a diagram which shows groupings based on primitive and shared derived characteristics.

Convergent evolution

where species from different lineages show similar characteristics because they are subject to similar selection pressures.

Divergent evolution

a pattern of evolution where an ancestral species evolves into a number of distinct species due to exposure of different populations to different selection pressures.

Figwort

a family of angiosperms.

Homologous trait

Structures that are similar because of shared ancestry, but that may have different functions due to divergent evolution, e.g. the pentadactyl limb of man and bats.

Molecular clock

using the number of differences in DNA or amino acid sequences to deduce how long ago species split.

node

point on a cladogram where divergence occurs. Also called a branching point.

root of cladogram

point prior to any divergence where the organisms share certain characteristics (beginning of the tree diagram)

outgroup

most distantly related organism on a cladogram. It will be on the longest branch of the tree and will be set apart from the other branches.

phylogenic tree

diagram that represents evolutionary relationships among organisms based on physical and genetic similarities and differences.