Final answer:
Island dwarfism is an evolutionary process that causes changes in body size when small animal species colonize islands. Smaller bodies can be advantageous due to limited resources, while larger species may become smaller to adapt to the island environment.
Step-by-step explanation:
The phenomenon that causes changes in body size on islands is called island dwarfism. This evolutionary process occurs when small animal species colonize islands where there are no key predators. In this environment, smaller bodies can be advantageous due to limited resources. On the other hand, larger species may become smaller in order to adapt to the island environment.
For example, Homo floresiensis, a small-bodied hominin species found on the island of Flores, is believed to have evolved through island dwarfism. Its ancestors, Homo erectus, arrived on the island and became isolated, resulting in their descendants growing progressively smaller to make the most of the limited resources available.
The same phenomenon can be observed in other animal species found on islands, such as the dwarf species of primitive elephant called Stegodon found with Homo floresiensis. These observations support the island dwarfism hypothesis, which explains the changes in body size observed in certain species on islands.