Effects of different forms of selection on evolution Flashcards
What are the primary sources of genetic variation?
Mutation
Meiosis
Random fusions of gametes
What are selection pressures the result of and what do they result in?
Selection pressures are the result of predation, disease and competition. These selective pressures result in certain organisms with phenotypes that give them selective advantages making them more likely to survive
What is an advantage of certain organisms having selective advantages?
Since certain organisms having phenotypes that give them selective advantages they are more likely to survive and produce more offspring and pass on more favourable alleles to the next generation
When organisms with selective advantage pass on their genes, what is affected?
There is a change in allele frequency evolution
How many types of selection are there? What are these types of selection called?
There are three types; stabilising selection, directional selection and disruptive selection
What is stabilising selection?
Stabilising selection tends to eliminate extremes of phenotype range within population and capacity for evolutionary change
When does stabilising selection occur?
Stabilising selection occurs when environmental conditions are constant over long periods of time
What does stabilising selection preserve?
Stabilising selection preserves the average phenotype of a population by favouring average individuals, selection against extreme phenotypes
What is directional selection?
This is the selection for one extreme phenotype
How does directional selection occur?
Directional selection changes the phenotype of a population by favouring phenotypes that vary in one direction from the mean of the population
When does disruptive selection occur?
Disruptive occurs when an environmental factor (eg. temp) takes two or more distinct forms
What is disruptive selection?
Disruptive selection favours individuals with extreme phenotypes rather than those with phenotypes around the mean of the population
What can continued disruptive selection lead to?
Disruptive selection can lead to speciation
What does disruptive selection cause?
Disruptive selection causes the allele frequency to change and causes more individuals to possess the allele for the extreme trait and the middling trait alleles becomes less frequent
