allele
an alternative version of a gene
allele frequency
the proportion of all alleles that are of a specified type
crossing-over
the exchange of DNA between homologous chromosomes during meiosis
gene flow
a change in the gene pool caused by individuals entering or leaving a population
gene pool
the total set of genes of all individuals in a population
genotype frequency
the proportion of individuals in a population that have a particular genotype
Hardy-Weinberg equilibrium
the state of a population in which allele and genotype frequencies do not change between generations because evolution is not occurring
heterozygous
having two different alleles for a gene
homozygous
having two identical alleles for a gene
independent assortment
the random distribution of the pairs of genes on different chromosomes to the gametes during meiosis
locus (plural, loci)
the physical location of a gene on a chromosome
macroevolution
evolutionary change at or above the species level
meiosis
a process in cell division during which the number of chromosomes decreases to half the original number by two divisions of the nucleus, resulting in the production of gametes
microevolution
a change in allele frequencies within a population from one generation to the next
mutation
a change in DNA sequence
natural selection
a mechanism of evolution in which individuals that are better adapted to their environment survive and reproduce more successfully than less well adapted individuals do
nonrandom mating
reproductive pairing in which mates are chosen based on attributes or opportunity, not random selection
nucleotide
an organic compound consisting of a sugar, a phosphate, and a nitrogenous base; this compound forms the basis of a genetic sequence
population
an interbreeding group of individuals of the same species