3.7.3 Evolution May Lead to Speciation Flashcards
What are the five causes of evolution?
Mutation Gene flow Non-random mating Isolation Natural selection
What is evolution caused by?
A change in the allele frequencies in a population
What causes a non-evolving population?
Very large population
No migration
No mutation
Random mating
What is stabilising selection?
Where there is no environmental change
This tends to eliminate the extremes of the phenotypes
What is directional selection?
When the environmental conditions change, the optimum has changed
One extreme is favoured over the other
This causes a shift in the mean phenotype
What is disruptive selection?
Where the extreme phenotypes are favoured over the mean ones
It occurs when the environmental factor takes two forms
What is the allelic frequency?
The number of times an allele occurs within the gene pool
What is speciation?
The evolution of new species from existing ones
This involves reproductive separation
What is adaptive radiation?
The variations of alleles in the gene pools of different populations of species leads to each population becoming adapted to the local environment
What is genetic drift?
Smaller populations have a lower genetic diversity
This means that there is not an equal chance of each being passed on
Those passed on will quickly affect the whole population
This makes speciation occur faster
What is allopatric speciation?
Where two populations become geographically separated
The difference in environmental conditions between locations leads to a difference in natural selection
