Evolution Flashcards
Describe ‘Evolution’?
The changes in organism over generations as a result of genomic variations.
What is ‘Natural Selection’?
Natural selection is 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 changes phenotype frequency?
The changes in phenotype frequency as a result of stabilising, directional and disruptive selection.
Stabilising Selection
In stabilising selection, an average phenotype is selected for and extremes of the phenotype range are selected against.
Directional Selection
In directional selection, one extreme of the phenotype range is selected for.
Disruptive Selection
In disruptive selection, two or more phenotypes are selected for.
Describe natural selection in prokaryotes
Natural selection is more rapid in
prokaryotes. Prokaryotes can exchange
genetic material horizontally, resulting in
faster evolutionary change than in
organisms that only use vertical transfer.
Explain ‘Horizontal Gene Transfer’
Horizontal gene transfer is where genes
are transferred between individuals in the
same generation.
Explain ‘Vertical Gene Transfer’
Vertical gene transfer is where genes are
transferred from parent to offspring as a
result of sexual or asexual reproduction.
What is ‘Speciation’?
Speciation is the generation of new
biological species by evolution as a result
of isolation, mutation and selection.
What is a species?
A species is 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?
Isolation barriers prevent gene flow between subpopulations during speciation.
What barriers lead to Allopatric speciation?
Geographical
What barriers lead to Sympatric speciation?
Behavioural or Ecological
