Evolutionary processes

Explain the process of speciation. Compare/ contrast both allopatric and sympatric modes of speciation Explain how both allopatric and sympatric species are different to allopatric / sympatric speciation Explain how reproductive isolating mechanisms prevent gene flow Compare/contrast preygotic and postzygotic isolation and give examples of each (geographical, temporal, ecological, behavioural, structural barriers, polyploidy) of sympatric speciation Explain how instant speciation by polyploidy occurs (allopolyploidy, autopolyploidy) as an example Explain how ecological (niche isolation) speciation leads to sympatric speciation Describe what is meant by clines and ring species.

Allopatric speciation

Formation of 2 different species from an ancestral species. After a population has become divided by a physical barrier which prevents gene flow. Resulting in geographically isolated population.

Sympatric speciation

The formation of 2 different species from an ancestral species in the same geographical area and gene flow is stopped by a non-geographical barrier such as ecological isolation, sexual selection, or polyploidy

Allopatric species

Closely related species that are geographically seperated

Sympatric species

Closely related species that exist in the same geographical location.

Deme

Smaller group within the population that can freely interbreed. There is no or limited gene flow between demes

Cline

Gradient variation of a specific phenotype among a species from one point in the area to another point when species cover a large geographical area.

ring species

connected series of neighbouring populations arrnaged geographically in a ring, where adjacent populations can interbreed and share gene flow, but the two populations at the ends of the loop are reproductively isolated and cannot interbreed to produce fertile offspring

Reproductive isolating mechanism

Process that prevents different species from interbreeding and producing fertile offspring