Time Scales

• Ecological Time - refers to time scales reflective of life spans of organisms and periods of environmental change (usually 0-100 years; can be expanded up to 10,000 years)

• Geological Time - relates to the time frame over which geological processes occur (millions of years). Relevant to macroevolution

Taxonomy

• Linnaeus’ hierarchical system of classification reflects evolutionary relatedness

• The farther down you go in a hierarchy (e.g., phylum class family), the more closely related members of that group

• Groups at any level can be referred to as taxon (plural taxa)

Now view the hierarchy a little differently

Fig. 26.2

Binomial System of Nomenclature

• Two word name that is unique to a species

• Ursus americanus• Ceanothus americanus• Not a species without both names

Domains

• Similarities evident (principle of continuity and signature principle)

• Differences reflect evolutionary divergence (how long ago they split)

Phylogeny

• The evolutionary history of a species or a group of related species

• Used to track the relatedness of organisms over geological time

Morphology is an Important Part of Studying Phylogenies

• Primitive characters - morphological features that are present in a recent species and are also found in an ancestral species

• Derived characters - features present in a recent species but not in an ancestral species. Developed through evolution

Mor

pholo

gical

Phylog

enies

Phylogeny based on sequences encoding the proteincytochrome oxidase subunit II.

Fig. 26.19 – Cladogram of eukaryotes

A Mechanism for Diversification

• Horizontal (or lateral) gene transfer– Transfer of genes between different species

• Common between prokaryotes• Prokaryotes to eukaryotes• Eukaryote to eukaryote – less common

See figure heading for more complete explanation