Term | Definition |
complementary base pairing | either of the nucleotide bases linked by a hydrogen bond on opposite strands of DNA or double-stranded RNA: guanine is the complementary base of cytosine, and adenine is the complementary base of thymine in DNA and of uracil in RNA. |
convergent evolution | the process whereby organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. |
divergent evolution | the process by which a species evolves into two or more descendant or different forms; also, the process of tracing two or more species back to a common ancestor |
deoxyribonucleic acid | The molecule that carries genetic information in all living systems (see genetic code). The DNA molecule is formed in the shape of a double helix from a great number of smaller molecules |
double helix | The shape of a DNA molecule |
evolutionary change | a gradual change in the characteristics of a population of animals or plants over successive generations: accounts for the origin of existing species from ancestors unlike them |
gene flow | the transfer of alleles or genes from one population to another. Migration into or out of a population may be responsible for a marked change in allele frequencies (the proportion of members carrying a particular variant of a gene). |
genetic drift | the change in the frequency of a gene variant (allele) in a population due to random sampling of organisms. |
gradual change model | the punctuated equilibrium model of evolution, genetic drift, differential migration, mutation and natural selection. |
mutation | a sudden departure from the parent type in one or more heritable characteristics, caused by a change in a gene or a chromosome.an individual, species, or the like, resulting from such a departure. |
natural selection | the process whereby organisms better adapted to their environment tend to survive and produce more offspring. The theory of its action was first fully expounded by Charles Darwin and is now believed to be the main process that brings about evolution. |
nitrogenous base | a nitrogen containing molecule that has the same chemical properties as a base. they make up the building blocks of DNA and RNA: adenine, guanine, cytosine, thymine and uracil. |
non random mating | a mating pattern and a form of sexual selection in which individuals with similar genotypes and/or phenotypes mate with one another more frequently than would be expected under a random mating pattern. |
punctuated equilibrium model | A model of the theory that new species evolve suddenly over brief periods of time, followed by longer periods during which there is no genetic change. |
speciation | the formation of new and distinct species in the course of evolution. |
sugar-phosphate backbone | an important structural component of DNA. the part of the DNA molecule that twists around itself resulting in the right handed double helix structure. |