Finches found on the isolated galapagos island are different species with different beak sizes and shapes, but are otherwise similar to a finch species found on the south american mainland. what might be the cause of the differences in the development of the beaks of these galapagos finches?

Adaptive radiation .

Explanation:

All other finches species are evolved from original seed eating finches.

Plants produce hard seeds in dry season and soft in cold season.. Due to this finches beak get affected

answer and explanation;

volcanic rocks are igneous rocks which form from lava, molten rock which has been thrust out of a volcano onto the surface of a rocky body such as an asteroid, planet, or dwarf planet.  

plutonic rocks are igneous rocks which form from subterranean chambers of molten rock or magma. plutonic rocks make up the base of continental crust as well as oceanic crust. their slow rate of formation causes them to be coarse grained since there is plenty of time for large crystals to form before the magma solidifies into rock.

the textural difference is that plutonic rocks are more coarse grained than volcanic rocks. plutonic rocks are coarse grained while volcanic are fine grained ; glassey or fragmental. since fine and coarse are adjectives the decision as to whether a rock is fine or coarse grained is generally made on the bases of whether or not the individual crystals can be seen in most if the rock.