What evidence did darwin use to support his theory of evolution by natural selection?

The most famous of all the evidences that Darwin used to support his theory of evolution was of the Darwin's finches of the Galapagos islands off the shore of the mainland of Equador. He found that the physical traits like the beak size, body weight, and number of eggs laid, etc. depended on the type of food they ate and the environment of the islands. This observation paved way for establishing the process of natural selection in evolution.

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.

an organism's phenotype is the  form of a trait  that it  displays. for  flowercolor, a pea  plant  can  display  a phenotype of purple or white flowers. an organism's  genotype  is the alleles of a gene it contains. based on his data, mendel concluded that a phenotype can be  determined  by more than one  genotype.