The point at which the frequency of an allele in a population is 100% and, therefore, there is no more variation in the population for this gene.
A structure once useful to an organism but which lost its function as the organism evolved; examples are the human appendix and molars in bats that consume a liquid diet.
A measure of the relative reproductive output of an individual with a given phenotype, compared with that of individuals with other phenotypes.
A mechanism of evolution that occurs when there is heritable variation for a trait and individuals with one version of the trait have greater reproductive success than do individuals with a different version of the trait.
Similarities found in the body structures of organisms that, although modified extensively over time for to serve different functions in different species, are due to inheritance from a common evolutionary
The study and interpretation of distribution patterns of living organisms around the world.
The remains of a long–past organism, usually its hard parts such as shell, bones, or teeth, which have been naturally preserved; also, traces of such an organism, such as footprints.
The transmission of traits from parents to their offspring via genetic information.
An alteration of the base–pair sequence of an individual's DNA; may rise spontaneously or following exposure to a mutagen.
Selection that, for a given trait, increases fitness at one extreme of the phenotype and greatly reduces fitness at the other, leading to the prevalence of one extreme version of the trait in the population.
A method of determining both the relative and the absolute ages of objects such as fossils by measuring both the radioactive isotopes they contain, which are known to decay at a constant rate, and their decay products.
differential reproductive success
The tendency of some individuals to have greater reproductive success than other individuals in a population; one of the three conditions necessary for natural selection
A change in the allele frequencies of a population due to the movement of some individuals from one population to another; an agent of evolutionary change caused by the movement of individuals into or out of a population.
A change in allele frequencies of a population resulting from the isolation of a small subgroup of a larger population; all the
descendents of the smaller group will reflect the allele frequencies of the subgroup, which may be different from those of the larger source population. The founder effect is one cause of genetic drift.
A group of organisms of the same species living in a particular geographic region.
The process by which, as a result of natural selection, organisms become better matched to their environment; also, a specific feature, such as the quills of a porcupine, that makes an organism more fit.
A random change in allele frequencies over successive generations, a cause of evolution.
Selection that, for a given trait, increases fitness at one extreme of the phenotype and greatly reduces fitness at the intermediate point of the phenotype range; these populations thus have most members at either end of the phenotype range but relatively few in the middle.
Any characteristic or feature of an organism, such as red petal color in a flower or a cleft chin.
A process of natural selection in which features of organisms not closely related come to resemble each other as a consequence of similar selective forces; many marsupial and placental species resemble each other as a result of convergent evolution.
A change in allele frequencies of a population, which over time produce a population with new or modified characteristics.
A change in allele frequencies of a population due to famine, disease, or rapid environmental disturbance that causes a large proportion of the individuals in a population to die. causes genetic drift
Selection that, for a given trait, produces the greatest fitness at the intermediate point of the phenotypic range.
Behaviors that are learned easily by all, or nearly all, individuals of a species.
Any and all of the actions performed by an organism, often in response to its environment or to the actions of another organism.
Behaviors that do not require environmental input for their development; instincts are present in all individuals in a population and do not vary much from one individual to another or over an individual's life span; also known as innate behaviors.
The alteration and modification of behavior over time in response to experience.
fixed action pattern
An innate sequence of behaviors, triggered under certain conditions, that requires no learning, does not vary, and once begun runs to completion; an example is egg–retrieval in geese.
The total reproductive output of an individual.
The reproductive output that an individual brings about through apparently altruistic behaviors toward genetic relatives.
Costly behavior directed toward another individual that benefits the recipient with the expectation that, at some later time, the recipient will behave in a similar manner, returning the favor.
The process leading to an increase in the frequency of alleles for behaviors beneficial to the persistence of the species or population that are simultaneously detrimental to the fitness of the individual engaging in the behavior.
Kindness toward close relatives, which may evolve as apparently altruistic behavior toward them, but which in fact is beneficial to the individual performing the behavior.
A behavior that comes at a cost to the individual performing it and benefits another.