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Flashcards in Population and Genetics Deck (19):

who is Malthus? what was his theory?

carrying capacity

Left unchecked, human reproduction rates will rapidly outpace resource production, leading ultimately to “crime, disease, war, and vice.” (these being “natural” checks on population growth)

At the point where population size outstrips resource production, there are only two alternatives: find the means to expand the resource pool, or DIE


which organisms survive?

which organisms survive has to do with interactions among organisms, and between organisms and their environment


genotype and reproduction

genotype governs reproductive output and effects competitive ability


why is determining genotype complicated?

- phenotype may be similar for different genotypes

- environment effects may interfere with expression

- multiple genes may be implicated in a single phenotype


what happens when a population is in hardy-weingberg equilibrium?

the population is not evolving


what happens when a population is no longer in hardy-weinberg equilibrium?

no evolution because no charge in allele frequency!


other than a test cross, what's another way to asses the genotype of an organism? what's the equation?

Hardy-Weinberg Equation!!
models of population genetics

p+q = 1

p^2 + 2pq + q^2 = 1


what is p?

the frequency of the dominant allele


what is q?

frequency of the recessive allele


what is 2pq?

frequency of homozygous allele Aa


what is p^2?

frequency of AA

3/8 = .375 p^2


what is q^2?

frequency of aa

2/8 = .25 q^2


what happens to genotype frequencies in the absence of selection?

they'll go to Hardy-Weinberg equilibrium


what are the four assumptions of Hard-Weinberg?

1) mating is random
2) no natural selection
3) large population size
4) mutation and migration negligible


what could cause the relative frequency of alleles to change?


new allele and phenotype will appear in subsequent generations


why does HW equilibrium require no selection?

so all offspring have an equal chance of survival and reproduction


why does HW equilibrium require large population size?

because random events will have a large impact on small populations

genetic drift

a storm destroys 80% of the habitat and its inhabitants --> even if a population regains its original size, relative proportions of species are changed irrevocably


why must there be no migration or mutation for HW equilibrium?

no new alleles


why must there be random mating for HW equilibrium?

- sexual selection
- geographic variation and clines