change+over+time+glossary


 * SOMATIC MUTATION:** a mutuation that occurs in body cells (not passed on in sexually reproducing organisms)
 * GENE POOL:** the sum of all the genes and their particular alleles in a given population at a given time.
 * ALLELE FREQUENCY**: the number of each type of allele in a population
 * GENETIC DRIFT:** the loss of particular genes in a small population that results in certain genetic combinations not arising and others occuring infrequently. This can result in an inexpected change in evolutionary direction.
 * SELECTION PRESSURE:** a particular factor that favours individuals of a species possessing particular characteristics. For example, being green to camouflage and avoid predators. Natural selection, along with selection pressures, determine the traits possessed by individuals within a population and the overall genetic variation amongst these individuals.
 * BOTTLENECK EFFECT:** an environmental condition (event), as a result of which many individuals of a population are killed and only a small number survive (eg. a flash flood). This very likely results in the remaining individuals having a different gene pool to that of the original, larger population, and as such there is an overall reduction in the potential for new gene combinations and adaptations.
 * FOUNDER EFFECT:** occurs when a small number of individuals leave their ancestral population to form a new population in another isolated geographical region. As the size of this new 'founded' population, the variation present amongst individuals very likely won't reflect that exhibited in the ancestral population. Over time, the gene pool and the variation in individuals of the new population could become quite different from that of the ancestral population, generally as a result of genetic drift and natural selection.
 * GENE FLOW:** individuals move into the population or migrate out of it, resulting in a change to the gene pool of the original population.
 * SPECIES -** a population or group of populations whose members share similar characteristics and have the potential to interbreed and produce viable and fertile offspring.
 * ALLOPATRIC SPECIATION -** the formation of a new species resulting from the splitting of a population and the consequent //geographical isolation// of the resulting populations.
 * CONVERGENT EVOLUTION** - when two species, who do not share a recent common ancestor, independently develop similar features due to similar selection pressures.