Anole lizard species that occur together (sympatrically) on certain Caribbean islands occupy different habitats: some live only in the grass, some only on tree trunks, and some only on twigs. These species also differ morpho-logically: grass dwellers are slender with long tails, tree dwellers are stocky with long legs, twig dwellers are slender but stubby-legged. What is striking about these lizards is not that coexisting species differ in morphology and habitat use (such differences are common among closely related sympatric species), but that the same three types of habitat specialists occur on each of four islands: Puerto Rico, Cuba, Hispaniola, and Jamaica. Moreover, the Puerto Rican twig species closely resembles the twig species of Cuba, Hispaniola, and Jamaica in morphology, habitat use, and behavior. Likewise, the specialists for other habitats are similar across the islands.
The presence of similar species on different islands could be variously explained. An ancestral species might have adapted to exploit a particular ecological niche on one island and then traveled over water to colonize other islands. Or this ancestral species might have evolved at a time when the islands were connected, which some of these islands may once have been. After the islands separated, the isolated lizard populations would have become distinct species while also retaining their ancestors' niche adaptations. Both of these scenarios imply that specialization to each niche occurred only once. Alternatively, each specialist could have arisen independently on each of the islands.
If each type of specialist evolved just once, then similar specialists on different islands would be closely related. Conversely, if the specialists evolved independently on each island, then a specialist on one island would be more closely related to other types of anoles on the same island-regardless of their ecological niches-than it would be to a similar specialist on a different island.
Biologists can infer how species are related evolutionarily by comparing DNA sequences for the same genes in different species. Species with similar DNA sequences for these genes are generally more closely related to each other than to species with less-similar DNA sequences. DNA evidence concerning the anoles led researchers to conclude that habitat specialists on one island are not closely related to the same habitat specialists elsewhere, indicating that specialists evolved independently on each island.
It can be inferred that the DNA evidence mentioned in the highlighted text supports which of the following statements about the twig-dwelling anole lizards of any one of the four Caribbean islands mentioned in the passage?
They evolved from an ancestral species of twig dwellers at a time when their island was connected with the other three islands
They were once more similar morphologically to twig dwellers on the other three islands than they are at present
They are more closely related to tree- and grass-dwelling anoles on their island than they are to twig dwellers on the other three islands
Their habitat specialization as twig dwellers was influenced by the differences in the types of vegetation on the other three islands
Their DNA more closely resembles that of non-anole lizard species on their island than it does the DNA of anoles on the other three islands
此讲解的内容由AI生成,还未经人工审阅,仅供参考。
正确答案是 C。这是由于文章突出的内容支持:“生物学家可以通过比较不同物种为同一基因的 DNA 序列来推断物种之间的进化关系”。而 DNA 证据表明,一个岛上的特殊性物种与其他三个岛上的相同类型特殊性物种并不接近,这说明它们在每座岛屿上都是独立进化。因此,要找到答案,可以证实 C 选项,即根据其岛屿上其他树木和草地活动性的 anoles 来看,它们比其他三个岛屿上的树枝居住者更加接近。
因为每个岛屿之间的品种DNA 的差别更大,所以每个岛屿上的三个品种之间的联系更加紧密!
if the specialists evolved independently on each island, then a specialist on one island would be more closely related to other types of anoles on the same island-regardless of their ecological niches-than it would be to a similar specialist on a different island.
DNA evidence concerning the anoles led researchers to conclude that habitat specialists on one island are not closely related to the same habitat specialists elsewhere, indicating that specialists evolved independently on each island.
这两句话定位
因为每个岛屿之间的品种DNA 的差别更大,所以每个岛屿上的三个品种之间的联系更加紧密!
DNA evidence concerning the anoles led researchers to conclude that habitat specialists on one island are not closely related to the same habitat specialists elsewhere, indicating that specialists evolved independently on each island.
在每个岛屿上独立进化,意味着同一个岛屿上的3个种类之间更紧密联系
第三段:if the specialists evolved independently on each island, then a specialist on one island would be more closely related to other types of anoles on the same island-regardless of their ecological niches-than it would be to a similar specialist on a different island.说明如果是分开进化,那么每个岛上的互相会比不同岛上相同类型的更加related,而DNA就是证明了他们是分开进化,所以选C