Term | Definition |
Directional selection | The type of selection where one extreme phenotype is more advantageous than both the average and the other extreme phenotype. |
Pharmacogenetics | The study of how the actions of and reactions to drugs vary with the patient's genes. |
Allopatric speciation | Occurs due to populations becoming physically separated; it is
brought about by geographical barriers. |
Sexual selection | Natural selection arising through preference by one sex for certain characteristics in individuals of the other sex. |
Geographical barriers | These include mountains, deserts, oceans and rivers
that physically separate organisms and prevent populations from interbreeding |
Bioinformatics | The science of collecting and analysing complex biological data such as genetic code. |
Molecular clocks | An estimated rate of change over time of the nucleotide sequences of DNA molecules. |
Disruptive selection | The type of selection where those with extreme phenotypes have an advantage and those with average fitness are selected against. |
Founder effect | An example of genetic drift. Occurs when a new colony is started by a few members of the original population. |
Phylogenetics | The field of biology that deals with identifying and understanding the relationship between the different kinds of life on Earth, others use the term 'evolutionary relatedness'. |
Genetic drift | The change in allele frequency due to a chance event. Small populations that are isolated from each other can vary greatly due to changes in allele frequencies |
Sympatric speciation | A form of speciation where two species arise within the same
habitat. It occurs as a result of behavioural or ecological barriers. |
Stabilising selection | The type of selection where the average phenotype is selected and the extremes survive much less well, possibly even disappearing. |
Evolution | The changes that occur to a species over time, leading to offspring that are better adapted to survive in their environment than the previous generation. |
Natural selection | The mechanism by which evolution occurs. It is a process that
selects the phenotypes that are best suited to the survival of a species in its particular environment. |
Gene pool | The complete set of unique alleles in a species or population. |
Speciation | The evolutionary process leading to the formation of new species. |
Ecological barriers | These include factors such as temperature, pH, salinity, humidity and altitude which act to separate populations. |
Reproductive barriers | For example, if individuals in a population become fertile at different times of the year, their sexual organs change, or their courtship behaviour is different or unattractive, then the individuals cannot mate. |