2. Evolution requires genetic variation. Variation in alleles of genes occurs both within and among populations. Genetic variation is important because it provides the genetic material for natural selection. Genetic variation is brought about by mutation, which is a permanent change in the chemical structure of a gene. Polyploidy is an example of chromosomal mutation. Polyploidy is a condition wherein organisms have three or more sets of genetic variation
3. Natural selection is the gradual, non-random process by which biological traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution. Charles Darwin who intended it to be compared with artificial selection, which is now called selective breeding, popularized the term “natural selection.
4. Genetic drift or allelic drift is change in the frequency of a gene variant in a population due to random sampling. The alleles in the offspring are samples of those in their parents, and chance has a role in determining whether a given individual survives and reproduces. A population's allele frequency is the fraction of the copies of one gene that share a particular form. Genetic drift may cause gene variants to disappear completely.
5. Recombination can be thought of as gene shuffling. Most organisms have linear chromosomes and their genes lie at specific location (loci) along them. Bacteria have circular chromosomes. In most sexually reproducing organisms, there are two of each chromosome type in every cell. For instance in humans, every chromosome is paired, one inherited from the mother, the other inherited from the father. When an organism produces gametes, the gametes end up with only one of each chromosome per cell. Haploid gametes are produced from diploid cells by a process called meiosis.
6. Evolution is a change in the gene pool of a population over time; it can occur due to several factors. Three mechanisms add new alleles to the gene pool: mutation, recombination and gene flow. Two mechanisms remove alleles, genetic drift and natural selection. Except in rare cases of high gene flow, new alleles enter the gene pool as a single copy. The fate of any new allele depends a great deal on the organism it appears in. This allele will be linked to the other alleles near it for many generations. The effects of selection and drift are coupled. Drift is intensified as selection pressures increase. This is