macroevolution

macroevolution

describes evolution on a larger scale - above the species level, including the origination, diversification, and extinction of species and clades over long periods of time

microevolution

change in allele frequencies due to forces such as selection and drift

study changes in diversity by examining

origination rate

extinction rate

standing diversity

number of species present at a given time

origination rate (α)

appearance of new species

Extinction rate (Ω)

disappearance of species

Turnover

originations (α) + extinctions (Ω)

Adaptive Radiation

rapid production, from a single lineage, of many descendant species - many more originations than extinctions (α >> Ω)

1. these descendants have wide range of adaptive forms

2. adaptive radiations are observed as the sudden appearance of related diverse species in the fossil record or inferred by phylogenic analysis

three hallmarks of adaptive radiation

1. They are a monophyletic group

2. They speciated rapidly

3. They diversified ecologically into many niches

Adaptive radiation occurs when

1) Empty niches that they can exploit

2) Key innovations

Extinction

Converse of origination and diversification

A clade will endure only if its new species origination rate (α) is greater than the extinction rate (Ω) of species

Background extinction

refers to the normal rate of extinction for species or clades

Mass extinction

describes a statistically significant departure from background extinction rates that results in substantial loss of taxonomic diversity

What triggers mass extinctions?

Global events

-volcanic activity