Chapter23 Flashcards
Microevolution
Evolution on its smallest scale, as change in allele frequencies in a population over a population over generations.
Genetic Variation
Individuals in a population show differences in composition of their genes or other DNA segments.
Average Heterozygosity
Average percentage of Loci (part of chromosome) that are Heterozygous
Geographic Variation
Differences in the genetic composition of separate populations due to location
Cline
Example of Geographic Variation, a graded change in a character along a geographic axis of gradiant
4 Sources of Genetic Variation
Formation of New Alleles- Mutation
Altering Gene Number or Position- Chromosomal changes
Rapid Reproduction- faster rate of variation
Sexual Reproduction-Independent assortment, crossing over
Gene Pool
all copies of every type of allele at every locus in all members of the population
5 Conditions for Hardy- Weinberg Equilibrium
No Mutation- No change in the gene pool
Random Mating- Inbreeding Mixing of Gametes does not change
No Natural Selection-mate on a certain phenotypic trait
Extremely large population
No gene flow
Genetic Drift
Chance Events can cause allele frequencies to fluctuate unpredictably from one to another esp. in small pop.
Founder Effect
When few are separated and establish a new population whose gene pool differs from the source population .
Bottleneck Effect
A severe drop in population size can cause a substantial effect on the gene pool of a population
4 Effects of Genetic Drift
Significant in Small Populations
Allele Frequencies change at random
May lead to a loss of genetic variation in a population
May cause harmful alleles to be fixed.
Gene Flow
The Transfer of allele into or out of a population due to the movement of fertile individuals or their gametes
Relative Fitness
The contribution an individual makes to the gene pool of the next generation.
Directional Selection
Conditions favor individuals exhibiting one of the extreme phenotypic range shifting the pop frequencies.
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 an intermediate.
Sexual Selection
Certain inherited characteristics are more likely than other individuals to obtain mates
Sexual Dimorphism
Differences between phenotypes of the sexes.
Intrasexual Selection
selection within the same sex they compete directly for mates
Intersexual selection
When one mate chooses who to partner with.
Neutral Variation
Differences in DNA sequence that do not confer a select advantage or disadvantage
Balancing Selection
when natural selection maintains two or more forms in a population includes heterozygote advantage and frequency dependent selection
Heterozygote Advantage
individuals who are heterozygous at a particular locus have greater fitness than do both kinds of homozygotes defined in genotype not phenotype
