Chapter 21 - Species and Speciation

speciation

the process that produces new and distinct forms of life

biological species concept (BSC)

Species are groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups

morphospecies concept

members of the same species usually look alike

hybridization

closely related species can reproduce

wallace effect

there should be selection against hybridization

ring species

populations that can interbreed with neighboring populations but not with populations separated by larger geographical distances

limitations of the BSC and morphospecies concepts

Difficult to apply in real world

Cannot be applied to asexual or extinct organisms

Does not account for genetic exchange in ring species

Does not account for hybridization in plants

Ecological species concept (ESC)

The concept that there is a one-to-one correspondence between a species and its niche

- same niche, same species

Phylogenetic species concept (PSC)

the idea that members of a species all share a common ancestry and a common fate

- useful when thinking about asexual species

reproductive isolation

Separation of species or populations so that they cannot interbreed and produce fertile offspring

prezygotic reproductive isolation

separation of species due to factors that prevent the formation of a zygote

- behavioral

- physical

- temporal

- ecological

postzygotic reproductive isolation

Genetic incompatibility usually leading to failure of the zygote to develop

- Sterile offspring (genetic dead end)

allopatric

geographically separate

vicariance-derived speciation

A change in the physical environment causes allopatry

peripatric speciation

A specific kind of allopatric speciation in which a few individuals from a mainland population disperse to a new location remote from the original population and evolve separately.

adaptive radiation

speciation occurs quickly and a variety of ecologically distinct forms are generated as the organisms adapt to local conditions successfully

co-speciation

when organisms speciate in response to each other

sympatric speciation

The formation of new species in populations that live in the same geographic area

instantaneous speciation

Speciation that occurs in a single generation.

polyploidy

produces offspring who cannot reproduce with the parent generation

- in plants, result of extra set of chromosomes during cell division