Evolution And Natural Selection Flashcards
What is evolution?
The changes in organisms over generations as a result of genomic variations
What is needed for evolution?
Variation
Natural selection
Survival of the fittest
Describe variation
Mutations result in variation amongst individuals
Describe natural selection
Natural selection is the non random increase in frequency of DNA sequences that increase survival
Species produce more offspring that the environment can sustain
Selection favours those individuals who are best adapted
Less fit individuals die before they have the change to reproduce
Describe survival of the fittest
Only the fittest individuals survive to reproduce and pass on the genes that made them well adapted
What are deleterious sequences?
Individuals with an inferior version of a characteristic
They leave fewer offspring so fewer copies of those sequences leading to a non-random reduction in the frequency of that sequence
What is sexual selection?
The non-random increase in frequency of DNA sequences that increase reproduction
What is female choice?
The female selects a male that she considers to be of high quality based on the traits that he displays
She does this to ensure she has strong, healthy offspring with a high survival rate
What is male to male competition?
Where the males compete aggressively with one another for territories and access to females
This way only the strongest and most aggressive males with the best weapons successfully mate to pass the alleles for these characteristics on to the next generation
What are the three types of selection?
Stabilising
Directional
Disruptive
What is stabilising selection?
When selective pressures select against two extremes of a trait
What is directional selection?
One extreme of the trait distribution experiences selection against it so the populations trait distribution shifts towards the other extreme
What is disruptive selection?
Selection pressures act against individuals in the middle of the trait distribution resulting in a two peaked curve
