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