托福听力荟萃 09（在线收听）

Human populations near the equator haveevolved dark skin over many generations because of exposure to the fierce raysof the Sun. A similar phenomenon has also occurred in other parts of the animalkingdom. The African grass mouse is a good example. Most mice are______,but the African grass mouse is active during daylight hours. This means that itspends its days searching for food in the semidry bush and______habitats of eastern andsouthern Africa. Its______is______, like a______, which helps it blend in withits environment. Because it spends a lot of time in the intense______sun, the grass mouse has also evolved two separate safeguards against the Sun's______radiation. First, like the populations of humans in this region of the world,the skin of the grass mouse contains lots of______, or dark______. Second, and quite unusual,this mouse has a layer of melanin-pigmented______between its______and skin. This unique "cap" provides an extra measure of protectionfor the grass mouse and three other types of African mouse-like rodents thatare active during the day. The only other species scientists have identifiedwith the same sort of skull adaptation is the white tent-making bat of theCentral American tropics. Although these bats sleep during the day, they do socurled up with their heads exposed to the sun.

【填空答案】

nocturnal:adj. 夜行的，夜间活动的

scrub: n. 矮树，灌丛

fur: n. 毛皮

stripe: v. 划条纹

chipmunk: n. ［C］花栗鼠

tropical: adj. 热带的

ultraviolet:adj. 紫外线的

melanin: n. ［C］黑色素

pigment: n. ［C］色素

tissue: n. ［C］【生】组织

skull: n. ［C］头骨

【听力原文】

Human populations near theequator have evolved dark skin over many generations because of exposure to thefierce rays of the Sun. A similar phenomenon has also occurred in other partsof the animal kingdom. The African grass mouse is a good example. Most mice arenocturnal, but the African grass mouse is active during daylight hours. Thismeans that it spends its days searching for food in the semidry bush and scrubhabitats of eastern and southern Africa. Its fur is striped, like a chipmunk's,which helps it blend in with its environment. Because it spends a lot of timein the intense tropical sun, the grass mouse has also evolved two separatesafeguards against the Sun's ultraviolet radiation. First, like the populationsof humans in this region of the world, the skin of the grass mouse containslots of melanin, or dark pigment. Second, and quite unusual, this mouse has alayer of melanin-pigmented tissue between its skull and skin. This unique"cap" provides an extra measure of protection for the grass mouse andthree other types of African mouselike rodents that are active during the day.The only other species scientists have identified with the same sort of skulladaption is the white tent-making bat of the Central American tropics. Althoughthese bats sleep during the day, they do so curled up with their heads exposedto the sun.