Macroevolution: Sympatric Speciation

Allopatric speciation

the evolution of geographically isolated populations into distinct species. There is no gene flow, which tends to keep populations genetically similar.

Parapatric speciation

the evolution of geographically adjacent populations into distinct species. Divergence occurs despite limited interbreeding where the two diverging groups come into contact.

Sympatric speciation

occurs without geographic isolation, thus it occurs at a local level

Polyploidy

instant speciation which occurs in most often in plants.

Polyploid cells

containing more than two paired (homologous) sets of chromosomes.

abnormal cell division

Polyploidy may occur

Autopolyploidy

number of chromosomes double in the offspring due to total non-disjunction during meiosis.

Allopolyploids

polyploids with chromosomes derived from different species.

Gradualism

most speciation is slow, uniform and gradual.

Punctuated equilibrium

Most species will exhibit little net evolutionary change for most of their geological history
-Stasis

Punctuated equilibrium

occurs after some crisis