Population Genetics III
Natural Selection Principles:
1. Organisms produce offspring with different traits, which can be inherited.
2. Organisms produce more offspring than can survive because the world has limited resources.
3. Offspring whose traits are best suited to their environment survive and pass on those variations
to their offspring.
Natural selection acting on a gene involved in pigmentation in moths. Light colours used to be prevalent,
when the trees had a light colour. Industrial revolution caused the surfaces to be darkened, and the light
colours used to defend against the birds are no longer useful. Dark form became prevalent.
Fitness and natural selection: fitness is determined by the joint effects of genetic make-up and
environment. Absolute Fitness is then expressed by the number of offspring that survive to mate again.
Relative fitness is the ratio between the genotype and the most fit genotype.
Selection coefficient is s, a reduction in relative fit