The Evolution of Populations Flashcards
what is the unit of evolution?
-population is the unit of evolution. natural selection acts on individuals, but the population changes as a result
-accumulations of small changes lead to big changes = speciation
what is a gene pool?
total aggregate of genes in a population
what are a species and population?
species = interbreeding organisms, reproductively isolated from other species
population = local group of organisms in the same space
what is a fixed allele?
an allele with only one kind in a population - all members are homozygous - ex aa or AA
what is allele frequency?
the occurrence of a specific gene at a gene locus
ex - all white in cats is a dominant gene but only has a 3% frequency. chance of a WW cat is 0.1%
what is evolution, genetically?
a change in allele frequency in a population’s gene pool
what is the hardy weinberg principle?
a formula to use to determine if a population is evolving or not, by calculating genotype frequencies. if the predicted genotype frequency is not different than the real population, we say the population is not evolving
what is the hardy weinberg equation?
p^2 + 2pq + q^2 = 1
p = frequency of dominant allele
q = frequency of recessive allele
p^2 and q^2 = frequency of homozygous genotypes
2pq = frequency of heterozygous genotypes
what are the hardy weinberg conditions for genetic equillibrium (population not evolving)?
- large population = no chance to affect allele frequency
- mutations do not occur
- all genotypes have equal reproductive success / no natural selection
- no net flow of genes in / out of gene pool
- all mating in a population is random
what are the 3 key mechanisms responsible for genetic change?
- natural selection
- genetic drift
- gene flow
how does natural selection affect genetic change?
-organisms with favourable genes in their environment get passed on
what is genetic drift?
-when allele frequencies vary from one generation to another, reduces genetic variation
ex - if a population has 5 red flowers and 5 white ones, and only the whites reproduce, now the population has no genes for red flowers
what are the two types of genetic drift?
- bottleneck effect = population size is drastically reduced [bottlenecked] , now the remaining population has an under or over representation of certain alleles
- founder effect = a few individuals leave the original population, creating a new gene pool that differs from the original
what is gene flow?
the transfer of alleles into or out of a population due to movement of fertile organisms or their gametes, tends to reduce differences between populations over time
how do mutations affect genetic variation?
-mutations are the “raw material” for natural selection: one allele can get duplicated or substituted for another
