Question

why were different organisms found on each island of the galapagos?
the islands were connected by land bridges.
the climate and food sources on the islands varied.
organisms were the same from one island to the next.

Explanation:

The Galapagos Islands have different climates and food sources. Organisms adapt to their local environment. Different environments lead to different adaptations and thus different organisms. The islands were not connected by land bridges (they are separate). And it's not that organisms were the same (they vary as per the environment).

Answer:

The climate and food sources on the islands varied.