AH bio 2.2

what is evolution?

the change over time in the proportion of individuals in a population differing in one or more inherited traits

how can evolution occur?

the random process of genetic drift, or the non-random process of natural selection, or sexual selection

what does natural selection act on?

genetic variation in a poulation

what does variation in traits arise as a result of?

mutation

what is a mutation?

the original source of new sequences of DNA

what is natural selection?

the non-random increase in frequency of DNA sequences that increase survival and the non-random decrease in frequency of DNA sequences that decrease survival

since populations produce more offspring than the environment can support, what happens?

survival of the fittest

what is sexual selection?

the non-random process involving the selections of alleles that increase the individual's chance of mating and producing offspring

where is sexual selection more important?

habitats where food is abundant and predation is low

what can sexual selection lead to?

the evolution of sexual dimorphism

what are the two things that sexual selection can be due to?

male-male rivalry, female choice

what does genetic drift occur?

when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next

why is genetic drift more important in small populations?

alleles are more likely to be completely lost by chance from a small gene pool, and any change in allele frequency is likely to be more significant to the population as a whole

why might some alleles be randomly over represented or under represented following genetic drift?

the new population only carries a random sample of the original populations alleles

what are two commonly occurring examples of the effects of genetic drift?

population bottlenecks, founder effects

what are population bottlenecks?

when a population size is randomly reduced for at least one generation, so lowering the range of alleles upon which any subsequent selection pressures may then act

what are founder effects?

the isolation of a few random members of a population from a larger population, so the gene pool of the new population is not representative of that in the original gene pool

what happens when selection pressures are strong?

evolution is rapid

what do selection pressures measure?

how strongly a biotic or abiotic factor in the environment exerts its effect by influencing individuals in a population survive and pass in their alleles to the next generation

what are 4 biotic factors that can influence the rate of evolution

- competition
- predation
- disease
- parasitism

what are 5 abiotic factors that can influence the rate of evolution

- changes in temperatures
- light
- humidity
- pH
- salinity

wat does the hardy-weinberg principle state?

in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over generations

what is the set of conditions that the hardy-weinberg equilibrium can apply under?

- no natural selection
- random mating
- no mutation
- large population size
- no gene flow through migration

what can changes in the hardy-weinberg frequencies indicate?

that evolutionary influences are active

what is the equation for the hardy-weinberg principle?

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

what is fitness an indication of?

an individuals ability to be successful at surviving and reproducing

what is absolute fitness?

the ratio between the frequency of individuals of a particular genotype after selection, to those before selection

what does it mean if the absolute fitness is 1?

the frequency of the genotype is stable

what is relative fitness?

the ratio of the number of surviving offspring per individual of a particular genotype to the number of surviving offspring per individual of the most successful genotype

what is co-evolution?

the process by which two or more species evolve in response to selection pressures imposed by each other

what type of relationship is often seen between organisms experiencing co-evolution?

symbiotic

what happens in parasitism?

the parasite has a positive beneficial relationship with its host, which is negatively affected by the relationship.

what happens in mutualism?

the two species both derive positive benefits and, in most cases, each species cannot survive without the other

what happens in commensalism?

one species derives positive benefits from the relationship and the other is not affected/it is a neutral relationship

what does the red queen hypothesis state?

in a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species, and that species must adapt to avoid distinction

what do hosts that are better able to tolerate and resist their parasites have?

greater fitness

hosts become better able to tolerate and resist parasites. what does this make the parasites do?

adapt and increase their fitness in terms of virulence through exploiting their hosts for food, reproduction and transmission to new hosts