Life 21- Evidence and Mechanisms of Evolution Flashcards
Genetic drift
Changes in gene frequencies from generation to generation as a result of random (chance) processes.
Hardy-Weinberg equilibrium
In a sexually reproducing population, the allele frequency at a given locus that is not being acted on by agents of evolution: the conditions that would result in no evolution in a population.
Sexual selection
Selection by one sex of characteristics in individuals of the opposite sex. Also, the favouring of characteristics in one sex as a result of competition among individuals of that sex for mates.
Heritable trait
A trait that is at least partly determined by genes.
Frequency-dependent selection
Selection that changes in intensity with the proportion of individuals in a population having the trait
Artificial selection
The selection by plant and animal breeders of individuals with certain desirable traits.
Genetic structure
The frequencies of different alleles at each locus and the frequencies of different genotype a in a Medellan population.
Mutation
A change in the genetic material not caused by recombination.
Gene pool
All of the different alleles of all of the genes existing in all individuals of a population.
Population
Any group of organisms coexisting at the same time and in the same place and capable of interbreeding with one another.
Gene flow
Exchange of genes between populations through migration of individuals of movements of gametes
Natural selection
The differential contribution of offspring to the next generation by various genetic types belonging to the same population. The mechanism of evolution proposed by Charles Darwin.
Fitness
The contribution of a genotype of phenotype to the genetic composition of subsequent generations, relative to the contribution of other genotype so or phenotypes.
Stabilising selection
Selection against the extreme phenotypes in a population, so that the intermediate types are favoured.
Population bottleneck
A period during which only a few individuals of a normally large population survive.
Allele
The alternate form of a genetic character found at a given locus on a chromosome.
Directional selection
Selection in which phenotypes at one extreme of the population distribution are favoured.
Founder effect
Random changes in allele frequencies resulting from establishment of a population by a very small number of individuals.
Adaptation
(1) In evolutionary biology, a particular structure, physiological process, or behaviour that makes an organism better able to survive and reproduce. Also, the evolutionary process that leads to the development or persistence of such a trait.
(2) In sensory neurophysiology, a sensory cell’s loss of sensitivity as a result of repeated stimulation.
Disruptive Selection
Selection in which phenotypes at both extremes of the population distribution are favoured.
Neutral allele
An allele that does not alter the functioning of the proteins for which it codes.
Clinal variation
Gradual change in the phenotype of a species over a geographic gradient.
Trade-off
The relationship between the fitness benefits conferred by an adaptation and the fitness costs it imposes. For an adaptation to be favoured by natural selection, the benefits must exceed the costs.
