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Chapter 23: The Evolution of Populations

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Evolutionary change below the species level. Change in the allele frequecies in popuations over generations
The average percent of loci that are heterozygous.
Differences in the genetic composition of separate populations
Another way geographic variation occurs. A graded change in a trait along a geographic axis
A change in the nucleotide sequence of an organism's DNA
A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring.
Derived in 1908, this principle states that the frequencie sof all alleles and genotypes in a population will remain constant form generation to generation, provided that only Mendelian segregation and rocombination of alleles are at work.
The condition describing a non-evolving population that is in genetic balance
A process in which chance events cause cause unpredictable fluctuation in allele frequencies from on generation to the next. Its effects are most pronounced in small populations
Genetic drift that ocurs when a few individuals become isolated form a larger poplualtion and form a new population whose gene pool composisition is not relective of that of the original population.
Genetic drift that occurs when the size of a population is reduced, as by a natural disaster or human actions. Usually, the surviving population is no longer genetically representive of the original population.
The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes
Natural selection in which individuals at one end of the phenotypic range survive and reproduce more sucessfully than the other individuals
Natural selection in which intermediate phenotypes survive and reproduce more successfully than extreme phenotypes
Natural selection in which individuals on both extremes of a phenotypic range survive and reproduce more sucessfully than the other idividuals with intermediate phenotypes
A form of natural selection in which individuals with certain inherited chracteristics are more likely than other individuals to obtain mates
Marked differences between the two sexes in secondary sexual characteristics, which are not directly associated with reproduction or survival. May include differences in color, size, ornementation, and behavior
Selection within the same sex where individuals directly compete for mates of the opposite sex
(mate choice) Individuals of one sex (usually the females) are choosy in selecting thier mates from the other sex
Natural selection that maintains two or more phenotypic forms in a population
Greater reproductive success of heterozygous individuals compared with homozygotes. Tends to preserve variatin in gene pool
A decline in the reproductive success of individuals that have phenotype that has become too common in a population
Genetic variation that does not appear to provide a selective advantage or disadvantage.
the contribution an individual makes to the gene pool of the next generation, relative to the contribution of other organisms

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