mechanisms of evolution Flashcards
gene pool
all alleles within the population
allele frequency
% of each allele
microevolution
changing percentages of frequencies
factors that cause evolutionary change
- mutations
- gene flow (migration)
- non random mating
- genetic drift
- natural selection
factors that cause evolutionary change
mutations
changes in the dna of an individual
effect: changes allele frequencies by introducing new alleles
factors that cause evolutionary change
gene flow (migration)
when individuals move from one population to another
effect: change allele frequencies in either both populations through a ‘flow’ or movement of genes (alleles)
factors that cause evolutionary change
non random mating
individuals mating based on the selection of phenotypes or inbreeding
effect: increases proportion of homozygous individuals in a population, does not affect allele frequency
factors that cause evolutionary change
non random mating: preferred phenotypes
based on physical and behavioural traits
* prevents individuals with certain phenotypes from mating and only selected individuals contribute to the gene pool
factors that cause evolutionary change
non random mating: inbreeding
closely related individuals breed together
* homozygous genotypes become more common
* harmful recessive alleles are more likely to be expressed
factors that cause evolutionary change
genetic drift
random change in genetic variation due to chance
effect: changes allele frequency
factors that cause evolutionary change
genetic drift: founder effect
few individuals start a new isolated population
* ‘founders’ carry some but not all alleles from the original population’s gene pool, meaning diversity of new population is limited
factors that cause evolutionary change
genetic drift: bottleneck effect
rapid decrease in population size
* survivers only have a few of various alleles that were present in the larger population, gene pool now has less diversity
factors that cause evolutionary change
natural selection
environment selecting for individuals in a population with certain traits that make them better able to survive and reproduce
effect:
effect:allele frequency of many different genes may change, resulting in changes in the characteristics of a population
factors that cause evolutionary change
stabilizing natural selection
favours intermediate phenotypes, selects against extreme variants
factors that cause evolutionary change
directional natural selection
favours phenotypes at one extreme than the other
