ACT科学Session3地球学（实战练习Practice 5）

　　Practice 5

　　(52C-Passage II)

　　Fossil footprints of dinosaurs can be used to identify the type, size, speed, and gait of these animals. Determination of gait (the manner of moving on foot) is based on comparisons with speeds at which modern animals walk and run. Geologists performed the following studies to help estimate this information for some ancient footprints.

　　Study 1

　　A 68-million-year-old fossil trackway was discovered in a rock formation that consisted of alternating layers of mudstone and sandstone. A trackway is a path or trail commonly used by groups of animals. In the top mudstone layer, five sets of tracks were exposed that belonged to several species of two-legged dinosaurs. The tracks were oriented in the same direction and were formed at approximately the same time. Geologists concluded that two sets were made by meat-eating dinosaurs and the other three sets by plant-eaters. Measurements of the foot length and stride length (distance between successive footprints) of each set of dinosaur tracks were taken at the trackway.

　　Study 2

　　A geologist measured the skeletons of meat-eating and plant-eating dinosaurs in a museum. Table 1 shows the leg length, foot length, and ratio of leg length to foot length for those museum specimens.

　　Study 3

　　The leg length of the five dinosaurs from Study 1 was estimated using the data from Study 2. Their estimated speed was then calculated from modern animals that have stride-length-to-leg-length ratios similar to those of dinosaurs. Table 2 shows the calculated leg length, calculated speed, and gait of the dinosaurs.

　　Practice 5.1

　　A geologist hypothesized that speed is related to, the cold- or warm-bloodedness of an animal and that warm-blooded animals usually move at higher speeds. If this is true and some dinosaurs were known to be warm-blooded, which dinosaur in Study 3 was most likely warm-blooded?

　　A. Meat-eater 1

　　B. Meat-eater 2

　　C. Plant-eater 1

　　D. Plant-eater 3

　　Practice 5.2

　　Based on the information provided by the three studies, one can make the generalization that if:

　　F. speed is known, the type of dinosaur can be determined.

　　G. stride length and leg length are known, a dinosaur’s speed can be estimated.

　　H. leg-length-to-foot-length ratio is known, the weight of the dinosaur can be calculated.

　　J. the type of food a dinosaur ate is known, its gait can be determined.

　　Practice 5.3

　　The information gathered in Study 2 was necessary because it:

　　A.showed the exact species of the dinosaurs in Study 1.

　　B. allowed the geologist to estimate the speed of the dinosaurs in Study 3.

　　C. determined the age of the fossil trackway discovered in Study 1.

　　D. helped to identify the rock types in the formation of Study 1.

　　Practice 5.4

　　A fossil trackway is found in an exposed sandstone layer that is less than 20 million years old. The tracks belong to a large flightless bird. Would Studies 1. 2, and 3 need to be modified to estimate the speed of this bird?

　　F. Yes, because measurements should be done on museum skeletons of fossil flightless birds.

　　G. Yes, because Study 1 used more than one set of tracks.

　　H. No, because birds are thought to be the ancestors of dinosaurs.

　　J. No, because the bird would have a speed that falls within the range of those of the dinosaurs in Table 2.

　　Practice 5.5

　　Another section of the trackway, 100 m farther down the path from the first site, is discovered. All five sets of tracks can be seen and are measured as in Study 1. It is found that Meat-eater 1 now has a speed of 4.6 m/sec, while the other speeds stayed the same. Which of the following conclusions is NOT consistent with the new data?

　　A. Meat-eater 1 has changed gaits from walking to running.

　　B. Meat-eater 1 will overtake the other four dinosaurs.

　　C. Plant-eater 1 is in the least danger of being overtaken by Meat-eater 1.

　　D. Plant-eater 3 is in the most danger of being overtaken by Meat-eater 1.

　　Practice 5.6

　　Which of the following alterations to the method of Study 2 would have made the results of Study 3 more accurate?

　　F. Measuring the skeletons of dinosaurs that belong to species of dinosaurs other than those in Study 1.

　　G. Measuring the skeletons of more specimens of the same species as those in Study 1.

　　H. Measuring only the foot length of modern animals of various types.

　　J. Measuring the foot length of the small front feet of two-legged dinosaurs.

　　Answers for Practice 4-6: Practice 5 C G B F B G

　　上海新航道学校作为业内良心ACT培训机构 ，坚持“英语”的理念，注重学术研究，注重培养学生的学习能力。想成为下一个高分学员?赶紧来新航道报名ACT培训班 吧!