natural selection

natural selection occurs in an environment when certain individuals with a trait that helps them survive and reproduce are more fit ti survive in an environment.

what dose it mean to be "fit"

fitness is measured by the individuals ability to survive and reproduce in a given environment


bird beaks

on one given island there were two kinds of birds, one kind of bird had thick strong beaks, the other had thinner weaker beaks. the birds with thicker stronger beaks ate the bigger seeds with thicker shells.the birds with thinner weaker beaks ate smaller seeds with thinner shells.

the availability of smaller seeds decreases. the population of birds with smaller weaker beaks declines until eventually they die off. this leaves only the birds with thicker stronger beaks surviving.

in this situation the thicker stronger beak is the helpful trait because it makes it easier to eat the seeds available in this environment

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many different things can cause natural selection in an environment. genetic variations can cause traits to arise that is helpful in an environment.

if a species struggles to survive in an environment, over hundreds of years it can adapt to make it easier to survive and reproduce