Key TermsChapter 22: The Mechanisms of Evolution
22.1-What facts form the base of our understanding of evolution?
According to Darwin, the major features of evolutionary change are:
oSpecies are not immutable, they change over time
oThe process that produces these changes is natural selection
Variations among individuals affect the chance that a given individual will survive
and reproduce. Darwin called this differential survival and reproduction of
individuals natural selection.
Artificial selection: individuals with certain desirable traits by animal and plant
Population: a group of individuals of a single species that live and interbreed in a
particular geographic area at the same time.
Adaptation: refers to the process by which characteristics appear to be useful to
their bearers evolve (evolutionary mechanisms), and to the characteristics
oAn adaptation is a phenotypic characteristic that has helped an organism
adjust to conditions in its environment.
For a population to evolve, its members much possess heritable genetic variation,
which is the raw material on which mechanisms of evolution act.
Heritable trait: a characteristic of an organism that is at least partly determined
by its genes. The genetic constitution that governs a characteristic is called a
genotype. A population evolves when individuals with different genotypes
survive or reproduce at different rates.
oTo explain the origin and maintenance of generic variation
oTo explain the patterns and organization of genetic variation
oTo understand the mechanism that cause changes in allele frequencies in
Different forms of genes, called alleles, may exist at a particular locus.