| A | B |
|---|
| Species | A group of organisms that can interbreed to produce fertile offspring |
| Population | The number of individuals of one species in an area |
| Community | The number of individuals of all species in an area |
| Competition | Occurs when two organisms attempt to occupy the same niche |
| Natural Selection | Organisms produce more offspring than the environment can support, which leads to only the best adapted surviving to reproduce |
| Variation | Differences which can occur within species (Intraspecific) or between species (Interspecific) |
| Stabilising Selection | Light and dark shelled snails are eaten by birds, leaving more middle range snails |
| Disruptive Selection | Middle range snails are eaten by birds, leaving light and dark shelled snails in greater numbers |
| Directional Selection | The lightest coloured snails are eaten by birds, causing snails to become gradually darker |
| Gene Frequency | The number of occurrences of a particular gene within a population |
| Allele Frequency | A measure of how common dominant and recessive alleles are for a particular population |
| Speciation | The formation of a new species |
| Gene Flow | Exchange of genes between different gene pools by e.g. Migration |
| Genetic Equilibrium | The number of dominant and recessive alleles stays relatively constant in a large, randomly mating population |
| Crossing Over | Exchange of sections of DNA between homologous pairs |
| Independent Assortment | Mendel's idea that alleles are inherited independent of other genes, due to the random nature of chromosomes being separated during meiosis |
| Mutation | A change in an organism's DNA which increases variation in a population |
| Migration | Introduction of new alleles to a gene pool due to the arrival of new individuals |
| Genetic Drift | Random changes in allele frequency of a population |
| Founder Effect | A few individuals form a new gene pool based on a limited mix of alleles. |
| Bottlenecking | A change in a gene pool due to survival of only a small portion of the population |
