Natural Selection Flashcards
Explain the Median Grown Finch Example:
Explain the Rock Pocket Mice Example:
What is positive directional selection?
Favours individuals on one end of the distribution of phenotypes. (Graph skewed left or right).
What is stabilising directional selection?
Favors those in the middle.
What is disruptive directional selection?
Favours those at either end (the extreme).
What is industrial melanism, and why is it important?
- directional selection
- incomplete dominance
- selection acts on dominant alleles faster than recessive
- favoured dominant alleles immediately increase in frequency.
- selection is not likely to drive a dominant allele to fixation as recessive alleles can hide in a heterozygous state.
- favoured recessive alleles are not exposed to selection initially bc they are likely to occur only in heterozygous genotypes.
- only recessive hemozygous begin to appear they quickly fix in the population
What are examples of stabilising selection?
- Birth clutch size
- birth weight of human babies
- number of fingers
- camouflage to match environment
What are examples of disruptive selection?
- Specialist seeding
- smal fish eat algea
- big fish eat small insects
What are examples of artisicial selection?
- humans chosen for traits
- agriculture
- dog breeding
What are examples of balancing selection?
- heterozygote advantage occurs when selection savours heterozygous individuals over homozygotes
- heterozygotic for sickle cell anaemia for protection against malaria.
Explain the role of fitness in Natural selection.
Fitness = success of an organism at surviving and reproducing and thus contributing offspring to future generations.
Explain the role of relative fitness in natural selection:
- (w) = describes the success of a genotype at producing new individuals.
- Relative fitness standardised by the success of other genotypes in the population ranges from 0-0.10.
- Able to:
1. calc exp frequencies using HWE.
2. Ratio of observed/expected
3. Relative fitness: AS>AA>SS
