Ch 5
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Created by:
spreadeagleoctopus on February 20, 2012
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41 terms
Terms | Definitions |
|---|---|
 natural selection | the differential success of individuals within the population that results from their interaction with their environment. |
| fitness | is measured by the proportionate contribution it makes to future generations |
| evolution | the process of natural selection results in changes in the properties of populations of organisms over the course of generations |
| adaptation | any heritable behavioral, morphological, or physiological trait of an organism that has evolved over a period of time by the process of natural selection such that it maintains or increases the fitness of an organism under a given set of environmental conditions. |
| gene | a stretch of DNA coding for a polypeptide chain, where one or more polypeptides make up a protein. |
| alleles | alternate forms of a gene |
| chromosome | one of a group of threadlike structures of different lengths and sizes |
| locus | the position occupied by a gene on the chromosome |
| homozygous | containing two identical alleles of a gene at the corresponding loci of a pair of chromosomes |
| heterozygous | containing two different alleles of a gene, one from each parent, at the corresponding loci of a pair of chromosomes |
| genotype | genetic constitution of an organism |
| phenotype | the outward appearance of an organism for a given charateristic |
| dominant allele | the expressed allele |
| recessive allele | the allele that is masked |
| co-dominant | If the physical expression of the heterozygous individual is intermediate between those of the homo-zygotes, the alleles are said to be ___________. |
| genetic differentiation | when genetic variation occurs among the sub-populations of the same species |
| gene pool | the sum of genetic information across all individuals in the population |
| frequency | refers to the proportion of a given allele or genotype among all the alleles or genotypes present at the locus in the population |
| target of selection | the phenotypic trait that selection acts directly upon |
| selective agent | the environmental cause of fitness differences among organisms with different phenotypes |
| directional selection | type of natural selection where the mean value of the trait is shifted toward one extreme over another |
| stabilizing selection | natural selection may favor individuals near the population mean at the expense of the two extremes |
| disruptive selection | when natural selection favors both extremes simultaneously, although not necessarily to the same degree, it can result in a bimodal distribution of the characteristic in the population |
| mutations | heritable changes in a gene or a chromosome |
| genetic drift | a change in allele frequencies due to random chance |
| migration | the movement of individuals between local populations |
| gene flow | the movement of genes between populations |
| Hardy-Weinberg principle | under conditions of random mating, and in the absence of natural selection, mutation, genetic drift, and migration, the frequency of alleles and genotypes in a population remains constant from generation to generation |
| assortative mating | selecting mates based on some phenotypic trait |
| positive assortative mating | occurs when mates are phenotypically more similar to each other than expected by chance |
| negative assortative mating | occurs when mates are phenotypically less similar to each other than expected by chance |
| inbreeding | the mating of individuals in the population that are more closely related than expected by random chance |
| inbreeding depression | consequences of inbreeding |
| Cline | a measurable, gradual change over a geographic region in the average of some phenotypic character |
| ecotype | a population adapted to its unique local environmental conditions |
| geographic isolates | the free flow of genes among sub-populations is prevented by some extrinsic barrier |
| subspecies | a taxonomic term for populations of a species that are distinguishable by one or more characteristics |
| adaptive radiation | the process in which one species gives rise to multiple species that exploit different features of the environment, such as food resources of habitats |
| phenotypic plasticity | the ability of a genotype to give rise to different phenotypic expressions under different environmental conditions |
| developmental plasticity | differences in phenotypic traits for a given genotype under different environmental conditions reflect differences in the allocation of biomass to different tissues during the growth and development of the individual plant |
| acclimation | reversible phenotypic changes in an individual organism in response to changing environmental conditions |
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