What is natural selection?

Natural selection is when certain characteristic are 'selected' for. Each species have simiar characteristics but differences in genes means that their characteristics can vary for example individual birds of the same species have varied beak lengths. The environment favours certain characteristics, for example if a population of birds live on an island where there are just nuts to eat, the birds with shorter stronger beaks are favoured as they can crack open the nuts. This means that birds with genes for shorter beaks are more likely to survive and live long enough to breed and pass on their genes to their off spring. Birds without this gene are less likely to survive and die before breeding so don't pass on their genes. Over many generations all the individals of the species will have shorter stronger beaks. This whole process is called nsatural selection and allows species to adapt to thier environment.