Species and Speciation

Flashcards covering key concepts related to the definition, formation, and isolation of species.

What is the definition of a phylogenetic species?

An irreducible (basal) cluster of organisms diagnosably different from other such clusters, and within which there is a parental pattern of ancestry and descent.

What is the evolutionary species concept?

A single lineage of ancestor-descendant populations of organisms that maintains its identity from other such lineages

What are reproductive isolating barriers?

Mechanisms which prevent interbreeding between different species.

Does the ability to interbreed guarantee that populations are the same species?

No, the ability to interbreed does not necessarily indicate populations are the same species.

What are the two basic types of reproductive isolation barriers, based on zygote production?

Prezygotic barriers (no zygote produced) and Postzygotic barriers (zygote is produced).

What is the difference between prezygotic and postzygotic isolation?

Prezygotic isolation occurs before the formation of a zygote, while postzygotic isolation occurs after the formation of a zygote.

What are extrinsic postzygotic barriers?

Factors that cause hybrid inviability or sterility due to the environment.

What are intrinsic postzygotic barriers?

Hybrid inviability or sterility due to genetic incompatibilities within the hybrid offspring.

What is Dobzhansky-Muller Incompatibility?

Incompatible interactions of genes that can lead to postzygotic isolation.

What is the consequence of chromosome fusion in hybrids?

Meiosis problems.

Are reproductive isolation barriers necessary for speciation?

No, they are not necessary, but they can play a significant role in keeping species separate.

What is a very fast cause of speciation?

Polyploidy

What is the paradox of causes of speciation?

Reproductive isolation reduces reproductive success in individuals, yet it leads to speciation.

What commonly starts speciation?

Geographic isolation.

When does selection favor prezygotic mechanisms?

When postzygotic mechanisms are already present and when populations are sympatric.

What tends to counter divergence by selection or genetic drift?

Gene flow.

What type of isolation is usually required to start speciation?

Geographic isolation.

What are the three geographies of speciation?

Allopatric, Sympatric, and Parapatric.