Evolution Flashcards
population genetics
the frequency at which
different alleles occur in a population affects
the overall characteristics of the population
allele frequencies
how common
the alleles for a gene are in a population
hardy-weinberg principle
hardy-weinberg principle states that allele
and genotype frequencies of populations do
not change when assumptions are satisfied.
- no mutation
- random mating
- no trait advantages
- large population
- no migration
hardy-weinberg equation
equations are limited
to a specific situation:
- sexual population
- autosomal gene
- clear generations
- two alleles for gene
- diploid organism
evolution
evolution is formally defined as a change in
allele frequencies of a population over time
- processes that drive evolution correspond to
assumptions of the Hardy-Weinberg model.
- no mutation -> mutation
- random mating -> nonrandom mating
- no trait advantages -> selection
- large population -> genetic drift
- no migration -> gene flow
mutation
mutation is the original source of all genetic
variation and essential for evolution
- produce new alleles but generally have a small impact on allele frequencies
gene flow
gene flow is the movement of alleles into or
out of a population, which can change allele
frequencies if the movement is large enough
and could bring new alleles to a population
- can increase or decrease alleles
genetic drift
genetic drift includes any changes in allele
frequencies of a population due to random
events, which could be just about anything
from gamete sampling to natural disasters
- small numbers are more at risk
- larger the sample size, the smaller the chance of gamete sampling
- can only decrease alleles
founder effect
changes in allele
frequencies when new populations arise
- new population is likely to have different allele frequencies than the source population, by chance
bottleneck effect
changes in allele
frequencies due to severe population losses
- high mortality strikes individuals at random
- bottlenecked populations likely to have different allele frequencies than original population, by chance
fitness
the ability of an individual to have
fertile offspring relative to other individuals
selection
selection occurs when individuals that have
certain heritable traits produce more fertile
offspring than individuals without the traits.
- natural selection
- artificial selection
- sexual selection
- favors individuals
artificial selection
the process of modifying living things (as plants and animals) by selective breeding controlled by human beings
gamete sampling
when genes are passed on to the next generation in frequencies unlike those of the parental population
natural selection
Trait variation exists in populations, and
at least some of the variation is heritable.
- Resources are limited in the environment,
which will inevitably lead to competition.
- Individuals with traits that are beneficial
in a specific environment are more likely
to survive and reproduce (higher fitness)
directional selection
a pattern in which one
extreme trait provides
greater fitness
stabilizing selection
a pattern in which a trait
that is intermediate will
provide greater fitness
disruptive selection
a pattern in which the
extreme traits provide
greater fitness
sexual selection
a form of selection that
favors individuals with traits that increase
the ability to obtain mates (and sometimes
significantly reduce the ability to survive)
asymmetry of sex
the idea that females
will invest more energy in offspring (eggs
or parenting) than males in many species.
- Females produce limited offspring and
should select the most attractive males.
- Males produce unlimited offspring and
should mate with any available female.
- Result will be competition between males.