Lecture 1 Flashcards
(20 cards)
what is the definition of an adaptation?
a characteristic that enhances the survival or reproduction of organisms that bear it, relative to alternative character states
is you dont have evolution what state is a population said to be in?
hardy weinberg equilibrium ( the same number of individuals in every generation have the same proportion of alleles)
what are the 4 evolutionary forces which disrupt populations from being in hardy weinberg?
1) mutation
2) genetic drift
3) migration ( gene flow)
4) natural selection
what counteracts divergence due to genetic drift?
migration (gene flow)
what is the effect of random changes in unselected allele frequency in smaller populations?
it occurs more and tends to lower heterozygosity which can cause isolated populations to diverge
define natural selection
differential survival and/or reproduction of classes of entities that differ in one or more characteristics
what is the equation of fitness?
probability of survival x average number of offspring for a class of individuals
what are 3 pieces of evidence proving natural selection?
1) correlations between traits and the environment
2) responses to experimental change in the environment
3) correlations between trait and fitness component
what is an example proving correlations between traits and the environment?
E.g guppy - colouration differs between predation rate - trade off between attracting females but not getting eaten
what is an example of responses to experimental change in the environment?
E.g guppy showed spot size matched the background when predation is high
what is an example of correlations between trait and fitness component?
E.g. fish increased number of spots when no predator was present - actively trying to stand out which is a fitness advantage because males are more attractive if their colouration is rare
what is males being more attractive if their colouration is rare an example of?
negative frequency dependent selection
what are 6 issues with detecting selection?
1) consequence of physics/chemistry - is it actually an adaptation?
2) genetic drift can spread traits which is not necessarily advantageous
3) ancestral state -exaptation
4) selection may be working silently not actually causing any change
5) selection may be working at the group level not individual level
6) linkage
what is an exaptation and an example?
adaptation that was previously advantageous but now serves a different purpose e.g. penguins have wings which aren’t used for flight they are used for swim
does recombination happen randomly?
no it appears by linkage disequilibrium where alleles appear together more oten than you would expect by chance
describe a reason for linkage disequilibrium linking to numbers of alleles ?
beneficial alleles grouping together -single alleles not very useful alone but together they are more powerful
describe a reason for linkage disequilibrium linking to structure of alleles ?
structural changes e.g. inversion - once inversion happens recombination cannot take place- those particular alleles will carry on for generations even if they aren’t beneficial
what is a hitchhiking allele?
where an allele with no benefit is next to a beneficial allele they are not likely to split by recombination so the allele carries through the generation
what is the name for hitchhiking alleles passing through generations? what is the issue with the?
selective sweep - could look at wrong gene and think it is beneficial when really it is just hitchhiking
what are 5 things natural selection will not do?
1) always lead to adaptation
2) produce perfection
3) always progress
4) produced a balanced harmonious world
5) consider ethics
