Final answer:
The Galápagos islands have different types of plants due to geological differences leading to soil variations. These variations in plant types explain the differences in beak shape in finches.
Step-by-step explanation:
The reason why each of the Galápagos islands had different types of plants is primarily due to geological differences leading to soil variations. Each island has unique geological characteristics, which affect the composition, fertility, and moisture content of the soil. These variations in soil types create different microhabitats with specific environmental conditions, supporting the growth of different plant species on each island.
These differences in plant types can explain the differences in beak shape in finches. The finches likely dispersed from one parent species, and natural selection based on different food sources in differing habitats led to adaptive changes, evidenced in the different beak shapes of the different species – each suited to a different food type. For example, finches with larger beaks are better equipped to crack open larger seeds, while those with smaller beaks are more efficient at eating smaller seeds.