Natural Selection Example & Extra Key Points November 2018 Biology 11

Example of Natural Selection: The Peppered Moth (Due to man’s effect on the environment) Background: Moths in pre – Industrial Revolution England were of 2 colors: light colored and dark colored.

Soot was rare in the English countryside. Light colored moths were difficult to see against the clean light colored bark. The dark colored moths were easily spotted by predatory birds and thus their numbers were fewer.

Due to coal burning during the Industrial Revolution, the light colored moth stood out against the dark, soot-covered bark. The light colored moths were easily spotted by predatory birds and so their numbers were fewer.

What do you think happened to the number of each type of moth after pollution control measures were taken and the country air became less polluted?

How does the environment affect which variations are expressed?

Natural Selection – Three Important Points Although natural selection acts on individual, individuals do not evolve A population (a group of interbreeding individuals of a single species that share a common geographical area) is the smallest group that can evolve Evolutionary change = changes in relative proportions of heritable traits in a population over successive generations

Natural Selection – Three Important Points Natural selection only acts on heritable traits that are passed from organism to offspring. Characteristics acquired during lifetime may enhance survival and reproductive success, but there is no evidence such characteristics can be inherited by offspring e.g. big muscles

Natural Selection – Three Important Points Environmental factors vary from place to place and time to time. A trait that is favourable in one environment maybe useless or even detrimental in another. E.g. Salt water fish or organism in the prairies