Fitness (often denoted in population genetics models) is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment. In either case, it describes the ability to both survive and reproduce, and is equal to the average contribution to the gene pool of the next generation that is made by an average individual of the specified genotype or phenotype. If differences between alleles of a given gene affect fitness, then the frequencies of the alleles will change over generations; the alleles with higher fitness become more common. This process is called natural selection.
An individual's fitness is manifested through its phenotype. The phenotype is affected by the developmental environment as well as by genes, and the fitness of a given phenotype can be different in different environments. The fitnesses of different individuals with the same genotype are therefore not necessarily equal. However, since the fitness of the genotype is an averaged quantity, it will reflect the reproductive outcomes of all individuals with that genotype in a given environment or set of environments.
Inclusive fitness differs from individual fitness by including the ability of an allele in one individual to promote the survival and/or reproduction of other individuals that share that allele, in preference to individuals with a different allele. One mechanism of inclusive fitness is kin selection.
Other articles related to "fitness":
... Genetic load measures the average fitnessof a population of individuals, relative to a hypothetical population in which the most fit genotype has become fixed ... number of genotypes in a population, each with its characteristic fitnessthe genotype with the highest fitnessis called Wopt ... The average fitnessof the whole population is the fitnessof each genotype multiplied by its frequency this is called mean fitness ...
Famous quotes containing the word fitness:
“Critics generally come to be critics not by reason of their fitness for this, but of their unfitness for anything else. Books should be tried by a judge and jury as though they were a crime, and counsel should be heard on both sides.”
—Samuel Butler (18351902)