Q23 the author of the passage compares the

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Q23: The author of the passage compares the relationship between an organism’s biological clock and its environment to the relation between a wristwatch and its owner most probably in order to A. point out a fundamental difference between the function of biological clocks in organisms and the use of mechanical clocks by humans B. illustrate the way in which the period of an organism’s biological clock can be altered by environmental factors C. suggest that there are important similarities between the biological clock in organisms such as the commuter diatom and the biological clock in humans D. support an argument regarding the methods used by certain organisms to counteract the influence of the environment on their biological clocks E. question the accuracy of the biological clock in organisms such as the commuter diatom Answer: ----------------------------------------------------------------------------------------------------------- - 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 25
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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 26
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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.
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