Biology 205 - Three
The Hardy-Weinberg Equation
- Allows us to determine whether evolution has occurred. - If the frequency of alleles changes between a parent generation and its offspring, evolution has occurred between the two generations.
Mutation
- Changes in the nucleotide sequence of DNA. - The source of new alleles and, along with sexual reproduction, the producer of genetic variation.
The Hardy-Weinberg Equilibrium (7 points)
- Evolution will not occur within a population if 7 conditions are met: 1. Mutation is not occurring. 2. Natural selection is not occurring. 3. The population is infinitely large. 4. All members of the population breed. 5. All mating is totally random. 6. Everyone produces the same number of offspring. 7. There is no migration in or out of the population.
Intersexual vs. intrasexual selection
- Intersexual: Mate choice. Individuals of one sex (usually females) are choosy in picking their mates. - Intrasexual: Selection amongst one sex. Ex: the more powerful male winning a battle for females.
Sympatric speciation
- New species arise within the same geographic area as the parent species. - Gene flow between the two can be caused by polyploidy (more than two paired sets of chromosomes), habitat differentiation, or sexual selection.
Population, population genetics, gene pool, microevolution, and allele
- Population: A group of individuals of the same species living in the same place at the same time. - Population genetics: studies how populations change genetically over time. - Gene pool: the total collection of genes in a population at any one time. - Microevolution: A change in the relative frequency of alleles in a gene pool over time. - Allele: One set of a pair of chromosomes.
Allopatric speciation
- Populations of the same species are geographically separated, separating their gene pools. - Changes in genetics may be caused by natural selection, mutation, or genetic drift. - Allopatric speciation increases within small population. - Ex: The Grand Canyon separated two species of antelope squirrels.
4 species classification methods I
1. Biological species concept: Defines a species as group of organisms whose members can breed and produce fertile offspring, but who do not produce fertile offspring with members of other groups. 2. Morphological species concept: Classifies organisms based on phenotypic (observable) traits. - Can be applied to asexual organisms and fossils. - Subjective.
3 ways natural selection can alter variation in a population
1. Directional selection: Acts against individuals at one of the phenotypic extremes. - Common during periods of environmental change, or migration to a different habitat. 2. Disruptive selection: Favours individuals at both extremes of the phenotypic range. - May occur in patchy habitats. - Animals camouflaged on different backgrounds. 3. Sexual selection: May lead to phenotypic differences between males and females (sexual dimorphism).
4 factors affecting allele frequency
1. Natural selection. 2. Novel mutations. 3. Genetic drift: Produces the founder effect - when a few individuals colonize a new habitat. - The small the group, the more genetic variation between the two populations. - Ex: Four moose brought to Newfoundland. 4. Gene flow: The movement of individuals or gametes/spores between populations.
4 species classification methods II
3. Ecological species concept: Defines a species by its ecological role or niche. - Ex: cichlids look similar but feed at different depths. 4. Phylogenetic species concept: Defines a species as a set of organisms representing a specific evolutionary lineage. - Morphology and DNA used in definition.
