Chapter 23: The Evolution of Populations Flashcards
Microevolution
Evolution on its smallest scale
Genetic Variation
Differences among individuals in the composition of their genes or other DNA sequences
Neutral Variation
Differences in DNA sequence that do not confer a selective advantage or disadvantage
Population
Group of individuals of the same species that live in the same area and interbreed, producing fertile offspring
Gene Pool
Consists of copies of every allele at every locus in all members of a population
Hardy-Weinberg Equilibrium
- Allele and genotype frequencies are constant
- Population is not evolving
- p + q = 1
- p^2 + 2pq + q^2 = 1
Adaptive Evolution
Evolution that results in a better match between organisms and their environment
Genetic Drift
Chance events cause allele frequencies to unpredictably fluctuate from one generation to the next (especially in smaller populations)
Founder Effect
- Few individuals become isolated from a larger population
- This smaller group may establish a population whose gene pools differ from the original population
Bottleneck Effect
Sudden change in the environment reduces the size of a population drastically
-Certain alleles are over-represented, under-represented, and absent
Gene Flow
Transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes
Relative Fitness
The contribution of an individual makes to the gene pool of the next generation relative to the contributions of other individuals
Directional Selection
- Conditions favor individuals exhibiting one extreme of a phenotypic range
- Shifts a population’s frequency curve for the phenotypic character in one direction or the other
Disruptive Selection
Conditions favor individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes
Stabilizing Selection
Acts against both extreme phenotypes and favors intermediate variants
