The Evolution of Populations Flashcards
Microevolution
A change in allele frequency in a population over generations
3 Mechanisms that cause allele frequency change:
- Natural Selection
- Genetic Drift
- Gene Flow
How do you find the number of alleles?
individuals x 2
Hardy Weinberg Equilibrium
p^2 + 2pq + q^2 = 1
5 conditions for non-evolving populations
- No mutations
- Random mating
- No natural selection
- Extremely large population size
- No gene flow
Genetic drift
Random changes in allele frequencies from one generation to the next (founder & bottleneck effect)
Founder Effect
Occurs when a few individuals become isolated from a larger population
-Allele frequencies can differ between populations
Bottleneck Effect
A sudden reduction in population size due to a change in environment
- Results in a gene pool unlike the original
Consequences of Genetic Drift
- Significant in small populations
- Can cause allele frequencies to change at random
- Can lead to a loss of genetic variation within populations
- Can cause harmful alleles to become fixed
Gene flow
Consists of movement of alleles among populations
- Reduces variation among populations over time and avoids inbreeding depression
Natural Selection
- Causes adaptive evolution
- Involves both chance and sorting
- Consistently increases the frequencies of alleles that provide a reproductive advantage and leads to adaptive evolution
Relative Fitness
Contribution an individual makes to the gene pool of the next generation
Directional Selection
Favours individuals at one end of the phenotypic range
Disruptive Selection
Favours individuals at both extremes of the phenotypic range
Stabilizing Selection
Favours intermediate variants and acts against extreme phenotypes
