exam 3 ppt 9 Flashcards
which of the HWE assumptions does not happen in sexual selection?
individuals mating at random
how many processes is evolution driven by?
evolution is driven by four processes that change allele frequencies
what are the four processes that change allele frequencies that drive evolution?
1) natural selection, 2) genetic drift, 3) gene flow, 4) mutation
what is the only adaptive mechanism of evolution?
natural selection
only ______ results in adaptations
natural selection
definition of adaptation
a feature that has become common in a population by natural selection, because it provides some improved function, leading to increased fitness
exps of adaptations
a behavior or anatomical feature that allows escaping predators, a protein or other compound with special physical/chemical properties, an anatomical feature that allows an organism to access resources (bats using echolocation, etc)
non-adaptive evolutionary mechanisms (listed)
genetic drift, gene flow, mutation
what do genetic drift, gene flow, and mutations cause?
they cause allele frequencies to change, but do not lead to adaptation
definition of genetic drift
a change in the frequency of an allele due to the random effects of small population size
what is genetic drift with respect to fitness?
it is random with respect to fitness
is genetic drift more pronounced in big or small populations?
small
what can genetic drift lead to?
it can lead to random loss or fixation of alleles
two things that cause genetic drift
founder effect, bottleneck
definition of founder effect
when a few individuals leave a population to establish a new population; reproductively isolated (ex: amish populations in US)
what alleles will the new population likely have regarding founder effect?
new population is likely to have different allele frequencies than the source population, by chance
definition of bottleneck
an extreme example where the population falls to a few surviving individuals; survivors have random traits, no specific reason they survived (ex: cheetahs)
what will the alleles be like in a bottleneck population from genetic drift?
bottlenecked population is likely to have different allele frequencies than original population, by chance
exp of founder effect in amish populations
amish people had higher frequency of the trait for polydactyly -> resulted in extra fingers/toes being more prevalent in kids now because of reproduction with themselves
why is population size important when it comes to genetic drift?
a smaller population= more likely to lose genetic variation more quickly/easier
definition of migration
the movement of individuals from one population to another; results in gene flow
if individuals that are migrating are producing, what does this lead to?
gene flow (alleles can come and go from populations)
exps of migration and gene flow
butterflies
consequence of migration/gene flow
populations become more similar -> gene flow “homogenizes” allele frequencies between populations
gene flow is ______ alleles
exchanging
genetic drift and gene flow measure…
change in allele frequencies
where do new alleles come from?
mutation
types of mutations
neutral (silent), beneficial or harmful (missense, nonsense, frameshift, etc)
types of beneficial or harmful mutations
missense, nonsense, frameshift
what is the ultimate source of genetic variation?
mutation
no mutation ->
no evolution of any kind
mutation alone is usually ____
inconsequential
mutation alone is usually inconsequential, but how can it become an important evolutionary process?
combined with natural selection, genetic drift, and gene flow, it becomes an important evolutionary process
