Mechanisms of Evolution Flashcards
Biological Species
Group of populations all of whose members actually or potentially interbreed and produce fertile offspring. Potentially form a single gene pool.
Population Genetics
Study of evolution within a biological species
Units of Evolution
Individuals do not evolve, they develop. Alleles move freely through a population in time-can be natural selection OR random processes.
Evolution
Change in allele frequency within a population
Populations
Species are groups of these. Populations are units of evolution-evolution below species level is known as microevolution
What are new alleles generated by?
Mutations-can be harmful or neutral. Provides selective advantage.
What does the Hardy-Weinberg Equilibrium model?
Allele frequencies in a population which is NOT evolving.
What does the Hardy-Weinberg Equilibrium model require?
Random mating, very large population size, no immigration or emigration, no natural selection, no mutations.
What are the two equations for Hardy-Weinberg Equilibrium?
p+q=1 and p2+2pq+q2= 1. q=homozygous recessive and p= homozygous dominant.
Why use Hardy-Weinberg if real populations don’t follow this model?
Deviations from Hardy-Weinberg suggest population is evolving. Can be used to estimate number of recessive alleles in a population-useful in public health. Basis for a complex math science of population genetics, which helps us to understand microevolution.
Genetic Drift
Allele frequencies vary greatly from generation to generation in small isolated populations due to chance. Chance disappearance of particular genes or alleles due to individuals dying or not reproducing. Can also be due to immigration bringing in new alleles.
Bottleneck Effect
Drift due to periods of extreme sudden population contraction followed by pop growth (ex: weather, illness).
Founder Effect
Population has few founders-accidental colonization of an island. Population allele frequencies may not reflect those of ancestral populations-sampling error.
Fitness
Relative contribution made by an individual in a population to the next gene pool of next generation-how many descendents an individual has.
Natural Selection is…
Microevolutionary-changes through feedback. Also works upon variation as it is expressed in phenotype-genotype follows.
Adaptive Change
Frequency of favoured alleles rises, deleterious alleles decrease.
Stabilizing Selection
Tends to be seen in stable environment, not favouring extreme phenotypes. Population becomes less variable.
Directional Selection
Stable or steadily changing environment, favouring an extreme phenotypic range.
Disruptive Selection
Seen in heterogenous environments. Eliminates middle of distribution. Population becomes more variable, divided into morphs.
Rosemary and Peter Grant
Studied medium ground finches on Daphne Major. Found that they were able to demonstrate morphological changes due to natural selection as environmental conditions changed.
Heterozygote Advantage
Heterozygote for a particular gene has selective advantage over homozygotes for either allele. Hidden variation must be heterozygous for sickle cell anaemia to be resistent to malaria.
Frequency dependent selection
Most common morph in a population in any given population is selected against. Rare morph has selective advantage until it becomes common in turn.
Sexual Dimorphism
Difference in appearance between sexes, not directly associated with reproductive organs. Produced by different selection pressures on sexes, may be result of competition for reproductive opportunities producing secondary sexual characteristics.Useful in competition with one sex, not useful otherwise.
Intrasexual Competition
Members of one sex compete directly with one another for opportunities to mate-opposite sex dates winner. (men in a bar fighting over hot woman)
Intersexual Selection
Members of one sex choose mates according to some criterion-results in secondary sex characteristics which are an apparent burden but actually signal good genotype (fancy ass birds being fancy).
