a change in allele frequencies in a population over generations
true
the physical expression of the genotype
variation in an individual's phenotype
false
genetic components
how much genetic variation there is between individuals
measure polymorphisms in a population by determining the amount of heterozygosity at the gene and molecular levels
average heterozygosity
nucleotide variability
average percent of loci that are heterozygous in a population
comparison between the dna sequences of pairs of individuals
changes in nucleotide sequence of dna
cause variability
only mutations in cells that produce gametes can be passed to offspring
formation of new alleles by mutation
altering gene number or position
rapid reproduction increases mutation rate
sexual reproduction shuffles existing genetic variation
a mutation that changes a single base in a gene
harmful and result in deletion by natural selection
usually harmful
duplicated genes that can take on new fuctions
low
very low, but their rapid reproduction makes them mutate quickly
random change in allele frequencies in a population
significant on smaller populations
causes allele frequencies to change at random
can lead to a loss of genetic variation
can cause harmful alleles to become fixed
when a few individuals get isolated from a larger population
when a population suddenly decreases is size due to a change in the environment
alleles moving among populations transferred by movement of fertile individuals or gametes
1) directional
2) disruptive or diversifying
3) stabilizing
favours individuals at one end of the phenotypic range
bell curve shifts over to one side
favours individuals at both extremes of the phenotypic range
bell curve splits into 2
favours intermediate variants and acts against extreme phenotypes
bell curve heightens
selection that preserves variation at some loci, maintaining two or more phenotypes in a population
a way for balancing selection to arise
when heterozygotes have a higher fitness than either homozygote
the fitness of an allele depends on its frequency in a population (declines when becomes too frequent)
marked differences between the sexes in secondary sexual characteristics
intra and inter
competition among the same sex for opposite sex
individuals of one sex are choosy in their mate
1) selection can act only on existing variations
2) evolution is limited by historical constraints
3) adaptations are often compromises
4) chance, natural selection, and the environment interact