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Speciation 7b - Coggle Diagram
Speciation 7b
Allopatric speciation
- This occurs when gene flow between two (or more) populations is prevented by a geographical barrier.
- e.g e.g. rivers, mountain ranges, desert, sea
- Random mutations in each sub-population give rise to new variation within each sub-group. New variation arises in each group that is not shared by the groups
- A geographical barrier separates the population into 2 isolated sub-populations. Interbreeding and gene exchange are no longer possible. Eg. sea, river, mountain range, desert, etc.
- -Different selection pressures act on each sub-population. This depends on local conditions like; climate, predators, disease.
-Natural selection affects each sub-group in a different
way, by favouring the alleles that allow the individual in that sub-populations to better exploit their environment.
- A large interbreeding population of one species exists in an environment.
- Over a very very long time…… Stages 3 & 4 cause the two gene pools to become so altered that the groups become genetically distinct & isolated.
- If the original barrier is removed, the two sub-populations are no longer able to interbreed There are now 2 separate distinct species. Speciation has occurred!
Sympatric speciation
- Two (or more) populations live in close proximity in the same environment but still become genetically isolated.
- This happens due to a behavioural or ecological barrier.
3) The two populations now exploit different resources (e.g. food source) and no longer interbreed.
-Behaviour has become an isolating barrier.
2) Alternative ecological niche appears. (e.g. new species of apple tree introduced by humans)
-Some members of the population start to exploit the new niche
4) Mutants better adapted to exploit the new resources appear and successfully breed. (e.g. better camouflaged on apples)
- Large interbreeding population sharing the same ecological niche. (e.g. Fruit flies living on hawthorn bushes)
5) Natural selection favours the new mutants and eventually over a period of time two genetically distinct species are formed which can no longer interbreed.
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Speciation
- Is the formation of a new biological species.
- It is brought about by evolutionary change.