ON THE ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION, Or the preservation of favoured races in the struggle for life FIRST: THE SE The SE is in exactly 2 weeks time! January 21st Next lesson, or the lesson next week, we will discuss the previous SE. This won’t take all lesson THE ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION What does that mean? http://www.youtube.com/watch?v=aTftyFboC_M THE ORIGIN OF SPECIES Ancient view: God created the world and all the plants and animals in it Species are fixed Darwin’s view: Species are not fixed! Species can adapt to new environments through the process of ‘natural selection’ (and sexual selection…) NATURAL SELECTION What is natural selection? Animals (on which we mainly focus) reproduce sexually What is sexual reproduction? Offspring get half their genes from the father, half their genes from their mother This creates a lot of variation NATURAL SELECTION This means that some of the offspring may be better adapted to the environment they are born in This increases their chance of survival! Is this enough? No Why not? They need to be able to pass their genes on to the next generation! SURVIVAL OF THE FITTEST What is meant with the ‘fittest’? FITNESS “the ability of an organism to produce viable offspring capable of surviving to the next generation” Animals with a high fitness are able to pass their genes on to the next generation. Therefor those genes continue to exist. If an animal fails to reproduce, his genes disappear This is why natural selection acts on the level of the gene! To be continued!