Speciation and Macroevolution

Adaptation

A heritable trait that helps an organism survive and reproduce in its present environment

Divergent evolution

Two species that evolve in difersifying directions

Convergent evolution

Similar traits evolve independently in species that do not share a recent common ancestry

Speciation

The formation of two species from one original species

Dispersal speciation

Allopatric - when few members of a species migrate to a new area

Vicariance speciation

Allopatric - when a natural situation arises to physically divide organisms

Polyploidy

Pairs of chromosomes separate, and the end cell product has extra sets of chromosomes

An error in meiosis which all of the chromosomes move into one cell instead of separating

Microevolution

Changes within a population of a single species, can lead to speciation

Macroevolution

Changes that occur above the species level, looking at patterns of speciation

Accumulation of speciation and extinction events

A species

A group whose members have the ability to interbreed and produce viable and fertile offspring, defined by reproductive isolation

3 - 4 BYA

In oceans, evolution of prokaryotes

2 - 3 BYA

Oxygenation of atmosphere

2 BYA

in oceans, eukaryotes

1.5 BYA

multicellularity

500 MYA

Diversification of animals, the cambrian explosion

400 MYA

Colonization of land

Mass extinction

Drastic loss of fossil diversity followed by rediversification

Three possible causes for extinction

1) volcanic flood

2) reduction in sea level

3) extraterrestrial impact