Selection Flashcards
what are the prerequisites for selection?
variation in fitness between phenotypes. variation needs genetic basis.
describe selection
- a non random process
- acts of differences
- leads to adaption
what is adaptation?
consequence of selection. beneficial function becomes prominent
what are some factors of fitness?
viability of zygotes. mating success of reproductive adults. fecundity of mating pairs. gamete compatibility
what is absolute fitness (W)?
genotype specific rate of increase that predicts the absolute number of indiviuals
what is relative fitness (w)?
fitness relative to one genotype, convention is that its relative to the fittest genotype
what happens if selections is against recessive phenotype?
lower fitness compared to the dominant
what is the selection coefficient (s)?
difference between relative fitness value and 1
describe selection for a dominant advantageous allele
- initially it can be selected for rapidly
- cannot be fixed by selection alone also genetic drift
how are deleterious recessive alleles affected by selection?
cannot be selected against when its in the heterozygous form
describe selection for advantageous recessive alleles
- first in the form of heterozygotes
- need a few homozygotes
- low at firs tthen shoots up
- at the same time selection against a dominant deleterious allele is very low
what does the response to selection depend on?
- allele frequencies (p and q)
- relative fitness of the genotypes
what are the different factors of response to selection?
heritability. strength of selection. allele frequencies. dominance of the allele. population size
what is directional selection?
one phenotype has a higher fitness - population moves towards this over time
what is stabilizing selection?
population already at the optimum - intermediates have a higher fitness
