1.7 Evolution Flashcards
What is evolution?
The changes in organisms over generations as a result of genomic variations
What is natural selection?
The non-random increase in the frequency of DNA sequences that increase survival and the non-random reduction in the frequency of deleterious sequences
What are the 3 types of selection that effect phenotype frequency?
Stabilising, directional and disruptive
What happens in stabilising selection?
An average phenotype is selected for and the extremes of the phenotype are selected against
What happens in directional selection?
One extreme of the phenotype range is selected for
What happens in disruptive selection?
Two or more phenotypes are selected for?
What is horizontal gene transfer?
Where genes are transferred between individuals in the same generation
Where is natural selection more rapid?
In prokaryotes. They can exchange genetic material horizontally, resulting in faster evolutionary change than in organisms that only use vertical transfer
What is vertical gene transfer?
Where genes are transferred from parent to offspring as a result of sexual or asexual reproduction
What is speciation?
The generation of new biological species by evolution as a result of isolation, mutation and selection
What is a species?
A group of organisms capable of interbreeding and producing fertile offspring, and which does not normally breed with other groups
Why are isolation barriers important?
They prevent gene flow between sub-populations during speciation
What are the different types of isolation barriers (and what do they lead to)?
Geographical - allopatric speciation
Behavioural and ecological - sympatric speciation
