Chapter 23 The Evolution Of Populations Flashcards
Adaptation
Natural selection improves the match between an organism and environment
Microevolution
Small scale, a change in allele frequencies in a population over generations
Genetic variation
Diff among ind in the composition of their genes or other DNA sequences
Mutation
A change in the nucleotide sequence of an organisms DNA
Population
A group of ind of the same species that live in the same area and interbreed, producing fertile offspring
Gene pool
Consists of all copies of every type of allele at every locus in all members of the pop
Conditions for hardy weinberg =
no mutations, random mating, no natural selection, extremely large pop size, and no gene flow
natural selectionq
individuals in a population exhibit variations in their heritbale traits and those with traits that are better suited to their environment tend to produce more offspring than those with traits that are not a well suited
adaptive evolution
evolution that results in a better match between organisms and their environmnent
genetic drift
chance events that can cause allele frequencies to fluctuate unpredictably from one generation to the next, especially in small pops
the founder effect
when a few individuals become isolated from a large population, this smaller group may estabilish a new pop whose gene pool differs from the source pop
the bottleneck effect
a suddne reduction in pop size due to a change in the environment
gene flow
the transfer of alleles in to or out of a pop due to the movement of fertile ind or their gametes
relative fitness
the contribution an ind makes to the gene pool of the next gen, relative to the contributions of other individuals.
directional selection
favors on extreme of phenotype
disruptive selection
favors both extremes of phenotypes
stabilizing selsction
favors intermediate variants
sexual selection
natural selection for mating success
sexual dimorphism
marked diff between the sexes in secondary sexual characteristics
intrasexual selection
within sex, in of one sex compete directly for mates of the opp sex, usually males
intersexual selection
female choice, ind of one sex are choosy in selecting their mates from the other sex
heterozygote advantage
hetero have increased fitness then do both homozygous
frequency dependent selection
the fitness of the phenotype depends on how common it is in the pop, scale eating fish
diploidy
maintains genetic variation in the form of hidden recessive alleles
why natural selection cannot make perfect organisms
selection can act only on existing variations, evolution is limited by historical constraints, adaptations are often compromises, chance, nat sel, and enviro interact
