Evolutionary Genetics Flashcards
evolution
changes in the genetic makeup of populations over time, sometimes resulting in adaptation to the environment and the origin of new species
natural selection
where there is variation in a population of organisms, the variants best suited to the environment have a greater chance of being passed down which leads to adaptations
types of variation
environmental variation - some apples develop in the sun, others in the shade
genetic variation - differences in genotype among individuals in a population. arises from mutations
tree of life
evolutionary theory predicts that new species arise by divergence of populations from a common ancestor.
- closely related species are more likely to look alike
- all of these relationships produce a tree
- branches are bacteria, archaea, eukaryotes
population genetics
patterns of genetic variation
gene pool
all the alleles present in all individuals in a population or species
population
all the individuals of a given species that live and reproduce in a particular place; one of the several interbreeding groups of organisms of the same species living in the same place
mutation
generates new variation
recombination
shuffles mutations
somatic mutations
affects individuals
germline mutations
passed down
mutations can be
neutral, deleterious (harmful) or advantageous (increase in frequency)
evolution in terms of genes
is the change in allele or genotype frequency overtime
- change in genetic makeup overtime
hardy Weinberg
when allele and genome frequencies do not change - absence of evolutionary forces
- no difference in survival and reproduction success between individuals
- populations must not be added to or subtracted by migration
- no mutation
- populations must be sufficiently large to prevent sampling error (no genetic drift)
- individuals must rate at random
hardy Weinberg equation
AA is p^2, Aa and pq and aa is q^2
p + q = 1
fitness
a measure of the extent to which an individual’s genotype is represented in the next generation
modern synthesis
the current theory of evolution, which combines Darwin’s theory of natural selection and Mendalien genetics
how does natural selection work?
increases frequency of favourable alleles
can cause allele fixation (frequency of 1)
postive selection
natural selection increase the frequency of a favourable allele
negative selection
reduces the frequency of a deleterious allele
balancing selection
natural selection that acts to maintain two or more allies or a given gene population
- populations in dry might favour one allele, populations in wet, another
- heterozygote advantage: heterozygous fitness is greater than either homozygote
stabilising selection
maintains the status quo and selects against extremes
- human birth weight
directional selection
select against one of two extremes and leads to a change in a trait overtime - finches
artificial selection
form of directional selection, similar to natural selection but without the competition. successful genotypes are selected by a breeder
disruptive selection
operates in favour of extremes and against intermediates. flies have evolved to eat apples or hawthorns but not both (might lead to speciation)
sexual selection
promotes traits that increase an individuals access to reproductive opportunities
- peacock tail
intrasexual selection: members of one sex compete for access to another sex
intersexual: interaction between males and females, as when females choose from males (bird dancing)
