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22 Cards in this Set

  • Front
  • Back
unit of evolution

-group of organisms of the same species at a particular place at the same time
population genetics
tracks the genetic makeup of populations over time
genetic trait with distinct phenotypes

--when a population includes two or more forms of a phenotypic characteristic, the contrasting forms are called morphs
population genetics
describing the genetic characteristics of populations
gene pool
all the genes in a population and their alleles
hardy-weinberg equilibrium
nonevolving population is in genetic equilibrium

-population's gene pool remains constant over time
-frequencies of alleles (p and q) and genotypes (p2, 2pq, and q2) are unchanged
change in a population's frequencies of alleles
sexual recombination
results in most of the generation to generation variability in human populations
Evolutionary forces that cause microevolution
1. genetic drift
2. gene flow
3. mutation
4. natural selection
genetic drift
random changes in allele frequencies due to sampling error in the production of gametes and fertilization

--changes are random and unpredictable (can't predict size/frequency)
--important in small populations
--genetic drift usually reduces genetic variation
--the smaller the population, larger amount of genetic drift
special kinds of genetic drift
bottleneck effect and founder effect
bottleneck effect
--genetic drift resulting from a drastic reduction in population size
--result of catastrophe
--survivors only contain a portion of the genetic variation present before the bottleneck
founder effect
small number of individuals leave a large population to colonize new, vacant habitat

--low variation
--different frequencies than source (bigger) population
Gene flow
the movement of alleles into or out of a population by migration

--reduces genetic differences between populations
random changes in the DNA

-produces new alleles
-source of genetic variation
natural selection (type of evolutionary forces for microevolution)
consistently adaptive
darwinian fitness
contribution of an individual to the gene pool of the next generation relative to the contribution of the other individuals

-determined by genotype
3 general outcomes of natural selection
1. directional selection
2. disruptive selection
3. stabilizing selection
directional selection
-selection shifts curve directionally
-often results from environmental changes
diversifying/disruptive selection
-selection against intermediate phenotypes
-can lead to different morphs being maintained in the population
-often occurs when environment is patchy
-different phenotypes favored in different patches
stabilizing selection
-maintains a narrow range of phenotypes
-selection against extreme phenotypes
-occurs in stable environments
things to note
1. selection for some phenotypes and against otheres
2. evolutionary change occurs when the environment changes
3. genetic variation must be present for populations to respond to changes in selection