[OLD] Populations - Evolution Flashcards
Describe allopathic speciation. (9 points)
Geographical isolation.
Creates separate gene pools with no interbreeding.
Variation due to mutation.
Different selection pressures
Selection for different advantageous alleles.
Differential reproductive success.
Leads to change in allele frequency.
Occurs over a long period of time.
Populations no longer able to interbreed.
What are the 4 factors that cause speciation?
Isolation
Mutation
Selection
Time
What happens to the allele frequency in stabilising selection?
It doesn’t change.
What type of selection is likely to lead to the development of new species?
Disruptive
What type of selection leads to a change in the mean?
Directional
What type of phenotypes are favoured in disruptive selection?
Extreme phenotypes.
What is the equation for allele frequency?
p + q = 1
What happens to allele frequencies in disruptive selection?
They increase.
Which phenotypes are favoured in stabilising selection?
Intermediate phenotypes.
What is a selective pressure?
A factor that drives selection
Why is hybridisation rarely successful?
Because of differences in the gene pools. If offspring are produced, they are rarely fertile.
Give the 2 main causes of geographical isolation.
Migration caused by overcrowding
Geographical hazards e.g volcanic eruptions, earthquakes, rivers, islands, roads
Describe sympatric speciation. (7 points)
Occurs in the same population.
Mutations cause variation.
Reproductive separation with no gene flow.
Different alleles selected.
Change in allele frequency.
Disruption selection.
Eventually different species which cannot interbreed.
What type of isolation occurs in sympatric speciation?
Reproductive isolation.
How does reproductive isolation cause speciation?
Individuals in the 2 populations may not be able to court each other, or mate with each other or produce fertile offspring. Now breeding can only occur with each gene pool, not between them.