Examples of places that show the effects of evolution
A. Madagascar
Madagascar is a large island that is actually a piece of a continent (not like Hawaii which is created by volcanoes) that is separated from other land masses. It has the highest level of endemism (i.e., organisms that only live there) on earth. For example of the 150 amphibians present there 148 are only found in Madagascar. 90% of all the reptiles and 100% of the rodents are only found in Madagascar. Lemurs are only found in Madagascar.
Why might this be so? Plate tectonic theory says that Madagascar used to be part of India and Antarctica and so the animals at that time were able to rove back and forth between these land masses. When Madagascar separated from India and Antarctica, the animals were isolated and since that time (when they had a common ancestor with Indian and Antarctican animals) they have evolved to look very different. This would also explain the presence of fossils on Madagascar that are related to the living animals there now.
B. The Hawaiian Islands
Like Madagascar, the plants and animals on Hawaii are almost completely different from anywhere else on earth. Unlike Madagascar, Hawaii is a set of volcanic islands. The animals and plants almost certainly came there from another continent. Yet they clearly have changed since arriving. Even on the islands, the species are often different from one island to another. Thus we can see that evolution has happened even between islands.
Consistent with the idea that the animals and plants have their common ancestors on the mainland, there is only one mammal native to Hawaii - the bat. Only the bat has been able to get to Hawaii. There are NO native reptiles, as no reptiles have been able to get across the over 1000 miles of open ocean to the islands.