Evolution may lead to speciation Flashcards
1
Q
Describe Allopatric Speciation
A
- Variation due to mutation gives rise to different alleles within a species
- species split into different groups due to geographical isolation
- no gene flow between different groups
- different selection pressures select different advantageous alleles
- organisms with advantageous alleles more likely to survive, reproduce and pass on the alleles increasing frequency of allele in population
- over period of time gene pools become so different that the different populations cannot interbreed to produce fertile offspring
1
Q
Define Sympatric Speciation
A
- Variation due mutation gives rise to different alleles within a species
- these species are not geographically isolated but instead reproductively isolated due to different mating seasons or different courtship behaviour
- no gene flow between different groups and therefore different allelic frequencies
- over period of time gene pools become so different that the different populations cannot interbreed to produce fertile offspring
2
Q
Describe Genetic Drift
A
- by chance, the allele of a particular gene is passed on to the offspring more often than other alleles of the same gene
- frequency of this allele increases over time
3
Q
What type of population does Genetic Drift have the most impact on and why?
A
- a small population
- less genetic variation and therefore, a lower ability to adapt to changing conditions.
4
Q
what is stabilising selection?
A
- natural selection favouring those with characteristics and phenotypes towards the middle of the range
5
Q
what is disruptive selection?
A
- natural selection favouring those with characteristics and phenotypes towards the either side of the range
- most likely to cause speciation as two separate population are likely to be formed
6
Q
what is directional selection?
A
- natural selection favouring those with characteristics and phenotypes towards one side of the range
