EVOLUTION
Charles Darwin
was the first to theorize evolution by means of natural selection. Evolution by natural selection is a process that includes:
1) more offspring are produced than what can possibly survive
2) traits vary among individuals, leading to different rates of survival and reproduction
3) trait differences are heritable
Thus, when members of a population die they are replaced by the progeny of parents better adapted to survive and reproduce in the environment in which natural selection takes place. This creates and preserves traits that are supposedly fitted for the functional roles that they are to perform. Natural selection is not the only known cause of evolution, other nonadaptive causes of evolution include mutation and genetic drift. (I do not personally believe in evolution, but for those who view the blog posts, this is for my AP Biology class.)
The Hardy–Weinberg principle (also known as the Hardy–Weinberg equilibrium)
- that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences. These influences include non-random mating, mutation, natural selection, genetic drift, and gene flow.
Because one or more of these influences are typically present in real populations, the Hardy–Weinberg principle describes an ideal condition against which the effects of these influences can be observed.
For example, a single fly with two alleles with frequencies (A) = p and (a) = q, respectively, the expected genotype frequencies are (AA) = p2 for the AA homozygotes, (aa) = q2 for the aa homozygotes, and (Aa) = 2pq for the heterozygotes. The genotype proportions p^2, 2pq, and q^2 are called the Hardy-Weinberg proportions. p + q must be equal to 1, and p^2 + 2pq + q^2=1.
