Define microevolution
Microevolution: change in allele frequencies within a population over generations.
How does non-random mating affect genotype vs. allele frequencies?
Alters genotype frequencies (increases homozygosity/heterozygosity), but does not change allele frequencies on its own.
Explain inbreeding depression and its two genetic hypotheses.
- Dominance hypothesis: recessive deleterious alleles are exposed. Deleterious alleles tend to be held at low frequency by selection against them and, at low frequency, they will be found predominantly in heterozygotes they can ‘hide’ in heterozygotes
- Heterozygote advantage: loss of beneficial heterozygotes.
How does gene flow differ from mutation as a source of genetic variation?
Gene flow introduces existing alleles from other populations; mutation creates new alleles. Gene flow rates are usually much higher and have a stronger, faster effect on allele frequencies.
Define genetic drift and explain its relationship with population size.
Genetic drift is a change in allele (gene variant) frequencies in a population that happens purely by chance, not because the allele is helpful or harmful. Genetic drift is a random mechanism of evolution: from one generation to the next, some alleles become more or less common just because certain individuals happened, by luck, to leave more offspring than others. This randomness can cause some alleles to disappear completely and others to reach 100% frequency (fixation), especially Stronger in smaller populations
What are the evolutionary consequences of genetic drift?
· Loss of genetic variation over time.
· Divergence between populations.
· Can overpower selection in small populations (fix deleterious alleles, lose beneficial ones).
What is a population bottleneck/founder event and what are its genetic consequences?
Severe reduction in population size (bottleneck) or when a small group of individuals colonizes a new geographic area, isolated from other populations (founder event). Reduces genetic diversity, increases drift, and can lead to high frequencies of deleterious alleles (e.g., Ellis-van Creveld syndrome in Amish populations).
State the three necessary and sufficient conditions for evolution by natural selection.
1) Individual vary in a trait
2) There is a non-random association between the trait and their reproductive success (i.e., ‘Darwinian fitness’)
3) The trait is heritable
fitness:
the (absolute) contribution of an individual to the next generation; its
reproductive success measured as the number of offspring in produces
Natural selection acts on ___________
Phenotype
