According to darwin why did the different population of finches become modified over time

While studying the finches, Darwin realized that any type of finch population consists of individuals that are different from one and another. When the individual with a phenotype characteristics would mate with another it would pass on the phenotype trait. This allowed for the trait to become more frequent as well as providing a survival advantage. Darwin named "descent with modification".

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Three reasons of the deaths of native americans: new illnesses that their immune systems couldn't cope with. genocides so the settlers could have the good land.starvation from lack of rations and poor infertile land on resevations