托福阅读真题+题目+答案：The Absence of Snakes in Ireland

托福阅读真题+题目+答案：The Absence of Snakes in Ireland

According to legend, lreland in northern Europe has no snakes because a fifth-century monk named Patrick drove the island's snakes into the sea. In reality, lreland has no snakes because of the interplay between organisms and their physical environment.

Snakes, like all reptiles and amphibians, are ectotherms (cold-blooded): their body temperature and functionality are dictated by the temperature of their external environment. Species diversity of reptiles decreases rapidly from the equator toward the higher latitudes. In North America, the number of lizard species is highest in the warm desert regions of the southwest and declines continuously as you move northward. The same pattern of species diversity is evident in Europe, where the number of reptile species declines markedly as you move from the warmer Mediterranean coast toward northern Europe and the British Isles. Although one snake species, the European adder (viper), is found above the Arctic Circle in Scandinavia, its unusually northern distribution comes at a cost. The adder has a very limited period of activity, often only three to four months a year. In addition, the species may take up to four years to attain sexual maturity, and females may breed only once every three or four years, using the intervening period to build up the fat reserves necessary to produce offspring.

1.Why does the author provide the information that“In North America, the number of lizard species is highest in the warm desert regions of the southwest and declines continuously as you move northward”？

O To contrast patterns of reptile diversity in North America with patterns elsewhere

O To help illustrate a general principle about the species diversity of reptiles

O To challenge a common belief about the preferred habitats of reptiles

O To make the point that snakes are less affected by external temperature than are lizards

2.The word “intervening" in the passage is closest in meaning to

O early

O other

O between

O long

3.According to paragraph 2, all of the following are costs of living above the Arctic Circle for the European adder EXCEPT

O producing only three or four offspring at a time

O reproducing only once every three to four years

O remaining inactive for most of the year

O living up to four years before producing offspring

The progressive decline in solar radiation and temperatures from the tropics to the poles not only reduces the abundance and diversity of reptiles but also has a direct influence on their body size. The reason for these patterns is that heat exchange occurs across the surface of a body, but warming usually occurs throughout the entire body's mass or volume. Large bodies, because of their low surface area to volume ratio, take longer to warm than smaller ones. ⬛ This physical reality results in upper limits to the size of snakes (and other reptiles) depending on the distance of the snake's habitat from the tropics. ⬛ All of the large snakes, such as the anaconda and python, are found within the tropic and subtropical regions. Other large reptiles- such as the iguanas, monitor lizards, and the crocodilians (alligators, caimans, and crocodiles)- -are likewise limited in their distribution to the warm, aseasonal environments of the subtropics and tropics. ⬛ The maximum body size for ectotherms declines as you move north and south from the equator. ⬛ This pattern is the exact opposite of that observed for endotherms (warm-blooded animals), where average body size increases from the tropics to the poles, a pattern referred to as Bergmann's rule. The environmental constraint on the upper limit of body size for ectotherms is at the very heart of the current debate over whether the dinosaurs were cold- or warm-blooded. The fossil record places the dinosaurs well into the northern latitudes, with specimens found in Alaska and Siberia.

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