Chinstrap and gentoo penguins are two species of penguins that feed on krill in the antarctic ocean. the two populations occupy the same area and have the same food source. they compete because they have the same niche. over many generations, gentoo penguins are driven to local extinction by competition with the chinstrap penguins. this is an example of

This is an example of natural selection which says that the species which is more adapted in their environment will survive and reproduce while the species who is less adapted will get extinct in the race of evolution.  

So the species who are more fit will survive and the species who is less fit will go extinct (survival of the fittest) because nature only selects the species who have the genes that help to adapt the species in changing natural environment.

Therefore in this question, Chinstrap penguin is more fit and adaptable to their environment than Gentoo penguins so in competition natural selection has favored Chinstrap penguin over Gentoo penguin, as a result, Gentoo penguins are driven to local extinction by competition with the Chinstrap penguins.