When Charles Darwin explored the geographically__26__ Galapagos Islands, he noted the great variety of beak shapes
on the finches there. It was later determined that Darwin’s finches made up 13 separate species. The similarities among the
species suggested a common ancestor: A single__27__of finch that came from the mainland of South America. How and why
did these birds evolve into genetically unique groups? With few native competitors and a wide variety of food sources, the
newcomers were able to begin occupying niches__28__ variations in beak shape and size. Finches with beaks that could__ 29__a particular food source – insects in the bark of trees,__30__ – slowly secured their own niche in the new habitat.
Natural selection thus favored beak specialization because it enabled many birds to adapt and coexist within the same__31__ . 【題組】28. (A) except for (B) in charge of (C) based on (D) in place of
寫作批改
VIP與詳解卡管理
私人筆記( 0 )