Question

Charles Darwin studied finches on the Galapagos Islands. While the finches on all the islands came from the same ancestors, the distance between the islands was too great to allow finches from different islands to interbreed. Over time, the size of the finches on the different islands remained the same, but the shape and size of their beaks changed, as shown here. This adaptation helped the finches find food on their particular island. The change in the size and shape of the finches’ beaks was MOST LIKELY caused by

Answer 1

Environmental selective pressures. In other words, natural selection took place. It was the environment that caused these changes. Birds on the islands with the most suitable traits for survival thrived while the birds that didn't die. 

Answer 2

Its A geographic Isolation