The Evolution of Populations

These flashcards cover key concepts related to microevolution, genetic variation, mechanisms of evolution, and selection processes as discussed in the lecture.

Microevolution

A change in allele frequencies in a population over generations.

Genetic Drift

A mechanism of evolution that describes how allele frequencies fluctuate unpredictably from one generation to the next.

Gene Flow

The movement of alleles among populations, which can reduce variation among populations.

Hardy-Weinberg Equilibrium

A condition in which allele and genotype frequencies remain constant from generation to generation in a population.

Point Mutation

A change in a single base in a gene that can affect protein production.

Stabilizing Selection

A mode of natural selection that favors intermediate variants and acts against extreme phenotypes.

Disruptive Selection

A mode of natural selection that favors individuals at both extremes of the phenotypic range.

Directional Selection

A mode of natural selection that favors individuals at one extreme end of the phenotypic range.

Founder's Effect

A phenomenon where allele frequencies in a small founder population differ from the larger parent population.

Ex. A flock of birds gets isolated from the mainland group and goes to a remote island and develops wierd looking peaks

Bottleneck Effect

A sudden reduction in population size that can result in a loss of genetic variation.

Ex. A large group of beetles that have a lot of colors gets nuked by a forest fire and now there’s a bunch of green and blue ones and only a few orange ones and yellow ones

Rules for hardy weinberg equilibrium

1. No mutations

2. No gene flow

3. Random mating

4. No natural selection

5. Extremely big population size

Rapid reproduction

Mutations are not seen as much. When they do happen they’re low on prokaryotes and high on diseases. They build up fast on prokaryorytes and diseases because they have a short life.

Sexual reproduction

Mixes existing alleles into new combos and are more important in sexually reproductive individuals bc it makes genetic differences and makes evolution easier

Population

Localized group on individuals that can inbreed and make fertile offspring

Gene pool

All the alleles for all the loci in the population and a locus is fixed if everyone in the population is homozygous

Natural selection

Certain alleles getting passed down because of successful offspring. Can cause adaptive evolution

Ex. Resistance to DDT in fruit flies became more common after mass usage in agriculture

Relative fitness

What an individual brings to the gene pool table compared to what other individuals bring for the next generation

Effects of genetic drift

1. Big impact on small populations

2. Can make allele frequencies randomly change

3. Can lead to less genetic variation

4. Can make harmful alleles fixed

Adaptive evolution

Adaptations caused by natural selection

Ex. A snake develops moving jaw bones to be able to swallow large food

Sexual selection

Natural selection for mating success, can result in sexual dimorphism which makes a species have secondary sexual characteristics (usually males) in order to get a mate

Male peacocks have large feathers to impress females

intrasexual selection

Direct competition for mates of opposite sex (usually males fighting)

Ex. Deers ramping horns to impress/win female

Intersexual selection

When individuals of one’s ex are picky choosing a mate of the opposite sex (usually females)

Balancing selection

When two or more phenotype forms stay stable via natural selection in a population (heterozygote advantage, frequency dependent selection)

Frequency dependent selection

If a phenotypic frequency becomes too common the fitness level decreases and so does interest

Ex. Too many blonds and now people want to reproduce with brunettes to even it out

Natural selection limits

1. Can only work on existing variations

2. Limited by historical constraints

3. Adaptations are compromises to environment

4. Chance and the encionrment play a role Int natural selection