It is the evolution of a new species which cannot interbreed with the original population following some kind of isolation.

There are two types of speciation: allopatric and sympatric.

Allopatric: Speciation taking place due to geographical isolation preventing gene flow.

Sympatric: Speciation taking place in the same geographic area. This is most likely caused by reproductive isolation.

Reproductive isolation

Hybrid sterility: odd number of chromosomes in a hybrid meaning they can't produce gametes.
Gametic: gametes released in the same place but chemical incompatibility means fertilisation is impossible.
Mechanical: Reproductive structures are incompatible.
Behavioural: Different mating calls not recognised by different species.
Temporal: organisms come in to season at different times so can't reproduce.

Pre-zygotic barrier: prevents fertilisation from happening.

Post-zygotic barrier: mating and fertilisation do occur but the offspring are not fertile.

	Created by Chloe Drewery almost 9 years ago

A level Biology (Chapter 20 - Patterns of Inheritance and Variation) Slide Set on Patterns Of Inheritance, created by Chloe Drewery on 10/12/2017.