Patterns on Natural Selection Natural Selection populations have

Patterns on Natural Selection

Natural Selection populations have a wide range of phenotypes, and genotypes some individuals in a population produce more offspring than others several types of natural selection affect the frequency of a heritable trait in a population A. Directional Selection favours ONE extreme phenotype e. g. , Giraffes

B. Stabilizing Selection favours intermediate phenotypes and acts against extremes e. g. , birth weight in humans, early mortality is highest for very high or very low birth weights C. Disruptive favours extreme phenotypes rather than the intermediate e. g. , rabbits with grey fur at a disadvantage compared to those with either black or white fur in an environment with patches of black and white soil

Natural Selection

Natural Selection D. Sexual Selection natural selection for mating based, in general, on competition between males and choice made by females this has led to sexual dimorphism: differences in males and females e. g. , colouration in birds, the peacock’s tail feather

Natural Selection E. Cumulative Selection Did the eye just appear suddenly in one generation? OR Did it evolve piece by piece over millions of generations? the complete eye we know today evolved gradually through a series of accumulated beneficial mutations the environment would have favoured the individual capable of sensing light get out of the sun or away from predators

One More Thing. . . Altruism one organism benefits much more from the behaviour of another organism than that organism itself “Fatal” part of Darwin’s theory e. g. , wasp colonies of females helping only 1 female to reproduce (sisters) WHY? may not pass on their genetics but at least passing on the genetics of the family