Q24 to Q27: Anole lizard species that
occur together (sympatrically) on certain Caribbean islands Line occupy different habitats: (5) 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 (10) slender with long tails, tree dwellers are stocky with long legs, twig dwellers are slender but stubby-legged. What is striking about these lizards (15) is not that coexisting species differ in morphology and habi- tat use (such differences are common among closely related sympatric species), but that (20) the same three types of habi- tat specialists occur on each of four islands: Puerto Rico, Cuba, Hispaniola, and Jamaica. Moreover, the Puerto Rican (25) twig species closely resembles the twig species of Cuba, Hispaniola, and Jamaica in morphology, habitat use, and behavior. Likewise, the spe- (30) cialists for other habitats are similar across the islands. The presence of similar species on different islands could be variously explained. (35)
An ancestral species might have adapted to exploit a particular ecological niche on one island and then traveled over water to colonize other (40) islands. Or this ancestral species might have evolved at a time when the islands were connected, which some of these islands may once (45) have been. After the islands separated, the isolated lizard populations would have become distinct species while also retaining their ancestors’ niche (50) adaptations. Both of these scenarios imply that speciali- zation to each niche occurred only once. Alternatively, each specialist could have arisen (55) independently on each of the islands. If each type of specialist evolved just once, then similar specialists on different islands (60) would be closely related. Conversely, if the specialists evolved independently on each island, then a specialist on one island would be more closely (65) 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. (70) Biologists can infer how species are related evolu- tionarily by comparing DNA sequences for the same genes in different species. Species (75) with similar DNA sequences for these genes are generally more closely related to each other than to species with less- similar DNA sequences. DNA (80) evidence concerning the anoles led researchers to conclude that habitat specialists on one island are not closely related to the same habitat specialists (85) elsewhere, indicating that spe- cialists evolved independently on each island. -------------------------------------------------------------------------------- Q24: The primary purpose of the passage is to - describe some unusual features of anole lizard species
- account for a particular type of behavior found among anole lizard species
- contrast two types of evidence that have been used to support a particular hypothesis concerning anole lizard species
- explain how researchers resolved a particular scientific question concerning anole lizard species
- examine different explanations for a particular trait common to certain anole lizard species
The answer is D, but I chose B. I think only last Paragraph is related to the how researches resolved sth. about lizard species. So D is narrowed. Can any NN explane? Thanks. | 
