Darwin is considered the "father of modern evolutionary biology." four of his contributions to the field of evolutionary biology are listed below.  the nonconstancy of species  branching evolution, which implies the common descent of all species  occurrence of gradual changes in species  natural selection as the mechanism for evolution (a) for each of the four contributions listed above, discuss one example of supporting evidence

nonconstancy of species

This is exhibited by the finches species of the Galapagos islands. While the finches belong to one species, they had phenotypic variations in beak sizes. Some had long narrow beaks while other had short stout beaks with variation in between. This increases the allele (genetic variation) in a gene pool.

branching evolution

The hip bone in whales which is homologous to that of humans depicts branching evolution. This exhibits that both species shared a common ancestor before they branched into different species. The hip in the whale has become vestigial while in humans it is prominent due to its purpose in the human gait and locomotion.

occurrence of gradual changes in species

Older fossils of a species best depict gradual change. This is when they are compared to those of current fossils of the same species. These fossils have displayed gradual differences in their structure and shapes. This is evident in the fossil of humans species that has shown gradual differences in structures such as the size and shape of the skull.

natural selection as the mechanism for evolution

When the predators such as lions during their hunting have preferences for fat prey (antelopes) since they are slower and provide more meat, this is natural selection forces at work on the prey population. The population of the fat and slow antelope will reduce because of being fed on more than the others. Therefore the subsequent generation of the antelope population will weed out fat antelopes.