chapter 5 Flashcards
(28 cards)
how is evolution defined by biologists?
as change in allele proportion in populations
what three factors are necessary for natural selection and what does each factor entail?
variations
these variations must be heritable and come from changes in genetics as a result of random mutation
these genetic variations much somehow impact an individual’s fitness
what does random mean in context of mutations and what word might be a better substitute for random?
it means mutations which occur regardless of whether they are useful to the individual or not, a better word might be indifferent
how do random mutations occur and what effects do most of them cause?
mutations come from dna replication errors and are mostly harmful or neutral
what is fitness?
an individual’s probability of leaving offsprings/passing on their genes to next gen
what is the relation of natural selection and randomness and what is a good phrase that describes it?
natural selection aka. filtering of mutated variants isn’t random/by change, rather mutation of variants which occur + get selected is random by change
“the non-random survival of random variants”
how do new traits evolve?
all new traits are modifications of earlier features
ex. legs of tetrapods = modified fins
what is a requirement for each stage of evolution/modification of an adaptive trait? what kinds of stages aren’t possible?
each stage must provide evolutionary benefits/increased fitness/increased average number of offsprings
stages can’t be temporary inconveniences/setbacks
how does evolution of fitness correlate w/ aging? what is an exception
since increased fitness only cares abt increased reproduction, genes which re favoured during youth may become negative in old age
an exception might be genes which help female humans survive post menopause
how does the phrase “for the good of the species” fit into the concept of adaption?
this phrase is false, adaptions only aim to increase fitness of individuals and will not nessecariliy be beneficial for the species as a whole
how does the phrase “for the benefit of the species” fit into the concept of adaption? and what is an example supporting this relationship
this phrase is false, adaptions only aim to increase the fitness of individuals and will not necessarily be beneficial for the species as a whole and may even have negative effects on overall species pop
ex. male lions displace resident male lions of a pride they kill all unweaned cubs of previous male
this is reduces pop of lions, but increases individual male lion fitness as can immediately fertilize females which increases genes passed to next gen
what is genetic drift?
genetic drift is where changes in frequency of alleles happens over time but not because of natural selection
what’s the diff b/w natural selection and genetic drift?
unlike natural selection, genetic drift is completely random
these random changes happen regardless of benefits/detriments while selection always gets rid of harmful alleles/physical features
how does genetic drift happen?
parents each have two copies of same gene and sexual reproduction randomly pairs up/passes down genes from parent to offspring
this means frequency of genes in each gen will be diff
new mutations may rise and fall due to random sampling
what changes can and can’t genetic drift make?
it can’t evolve adaptions (ex. build wings, eyes) but I can evolve features which aren’t harmful or helpful like mutations in pseudogenes
when is genetic drift strongest and how can this be negative?
genetic drift is more dominant in smaller pops
it can overpower natural selection and raise the frequency of harmful genes in a small pop
ex/ gacher’s disease in northern swedes, tay-sachs in canjuns, retinitis pigmentosa in tristan de cunha
might get rid of beneficial allele and fixate harmful alleles
why is the success of artificial selection important?
it acts as evidence to support the occurrence of natural selection
ex. sometimes results of artificial selection coincide w/ natural selection
greyhounds which are artificially selected for speed resemble cheetah which have been naturally selected for speed
what are the differences b/w artificial selection and natural selection?
natural selection happens much slower which is why there is such a large variation in domesticated species
good and bad traits are chosen based on human desire rather than natural environment/adaptation or increasing fitness
ex. svelte will turkeys are bread to have breasts so large males can’t mount females and have to be artificially inseminated, this wldn’t happen in wild as lowers fitness
what is stabilization selection and when does it happen?
stabilization selection keeps species at optimum state (ex. optimum body size) and culls individuals which are outside that state (ex. too big or too small)
what is microevolution?
small changes in onde or few features of an organism
what is microevolution?
small changes in onde or few features of an organism
what is macroevolution and why is it difficult to study and how do we make up for this?
transformation of one type of plant/animal into another, its hard to study since it can’t be observed within a human lifetime so ppl study fossil records to see how it’s occurred in the past
what kind of species is best for observing natural selection?
species w/ short generations which are adapting to new enviros/enviro changes
ex. after a drought on the Galapagos finches which usually prefer small soft seeds had to turn to larger hard seeds for food
this caused natural selection to favour finches w/ bigger + stouter beaks
by following gen average beak size increased by 10%
what kind of species is best for observing natural selection?
species w/ short generations which are adapting to new enviros/enviro changes
ex. after a drought on the Galapagos finches which usually prefer small soft seeds had to turn to larger hard seeds for food
this caused natural selection to favour finches w/ bigger + stouter beaks
by following gen average beak size increased by 10%
