U1.7 Evolution Flashcards
What is evolution?
The changes in organisms over generations as a result of genomic variations arising through mutations.
What is natural selection?
The weeding out of individuals of a species with a phenotype less suited to their environment.
What is natural selection the non-random increase in?
Frequency of DNA sequences that increase survival rates.
What is natural selection the non-random decrease in?
The frequency of DNA sequences that decrease survival rates.
What are changes in phenotype frequency in a population a result of?
Stabilising, directional, and disruptive selection.
What happens in stabilising selection?
An average phenotype is selected for and extremes of the phenotype range 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 phenotypes are selected for.
Describe natural selection in prokaryotes.
It is more rapid. Prokaryotes can exchange genetic material horizontally, resulting in faster evolutionary change than in organisms that only use vertical transfer.
What is horizontal gene transfer?
Where genes are transferred between individuals in the same generation.
What is vertical gene transfer?
Where genes are transferred from parent to offspring as a result of sexual or asexual reproduction.
What does horizontal gene transfer result in?
Rapid evolutionary change.
What is a species?
A group of organisms capable of interbreeding to produce fertile offspring, and which does not normally breed with other groups.
What is speciation?
The generation of new biological species by evolution as a result of isolation, mutation and selection.
Why are isolation barriers essential?
To prevent gene flow between sub-populations during speciation.
