Natural selection 2 Flashcards
Who recorded genetic linkage?
Was first recorded by Punnett and Bateson and refers to an exception to Mendel’s law of independent assortment.
What does Hardy-Weinberg’s equilibrium state?
Allele frequencies remain constant given certain assumptions.
Explain quantitative genetic traits
Consist of alleles that each have a small effect.
What is meant by ‘phenotypic plasticity?
Changes in a phenotype as a result of environmental conditions.
Why are there more differences in different dog breeds than there are for cats?
*Cats may have been selected over a shorted period of time
*Humans could see less practical uses for different forms of cats so they didn’t select them as strongly.
*Dogs had a greater Standing genetic variation to start with = presence of alternative forms of a gene (alleles)
What is evolution limited by?
Standing variation until new mutations accumulate.
What is heritability and give an equation?
Heritability is the proportion of phenotypic variation (VP) that is due to genetic variation (VG), where VE = phenotypic variation due to the environment.
VP = VG + VE + VGxE
H^2 = VG/VP
Give an example where a phenotypic trait is not heritable and simply environmental
The colours of hydrangea flowers from blue to pink
blue =acidic soil and pink= alkaline soil
What is broad sense heritability
*The fraction of the variance that is potentially due to genetic causes.
-Does not measure whether a trait has a genetic basis: no heritability does not mean the trait has no genetic basis.
Can selection operate on environmental variation?
No, selection can only operate on heritable traits only genetic variation not environmental variation
What allows evolution to occurs?
For evolution to occur, there needs to be trait heritability but also variation in fitness (how likely offspring will pass on those traits)
the average genetic contribution of a particular genotype or phenotype to the next generation
Selection typically acts on small differences in fitness:
How can we detect selection in the wild
*Experimental manipulation (guppy fish originally with adult feeding predator then switched to juvenile only feeder= guppy fish produced less but larger offspring)
*Trends associated with environmental change (great tit birds decreasing in size due to small bird houses which were originally made for blue tits.)
*Inter-specific comparisons ( mimicry of hoverflies to look like wasps)
*Changes in allele frequencies (mosquitos and resistance to DDT, big R allele increased in population for resistance but there is a cost to resistance so when DDT was stopped, mosquito alleles went back to optimum alleles so decreased back down to normal)
What is the correlation between size and mimicry in hoverflies?
If you are a larger hover fly mimicry is more useful as you will be more easily spotted by predators.
What are the modes of selection?
directional=e.g finches beaks increased after drought as plants producing bigger seeds were more successful
stabilizing=e.g human birth weight or galling flies attacked by parasitoid wasps better to have medium sizes galls
disruptive= lazuli bunting birds better to be either bright or dull
