2021年5月8日雅思考试机经完整版(3)

2023-06-03 12:03:55 来源：中国教育在线

2021年5月8日雅思考试机经完整版(3) 关于这个问题下面小编就来为各个考生解答下。

2021年5月8日雅思考试机经完整版(3)

2021.05.08

READING

Passage 1

Topic

Multiple intelligences

14为判断题

1. True

2. True

3. False

4. Not Given

5-13为填空题

暂无

Passage 2

Topic

Surviving the winter: Hibernation and other resting states

A. Many animals become inactive for periods of varying duration during the winter and.there is a diversity of terms used to describe this state, including: sleep, torpor,dormancy, lethargy and hibernation. The word hiberation is often used loosely to refero general inactivity but, in biology, it refers to a specific phenomenon, sometimes called true hibernation'. Hibemation is defined as the condition of passing the winter in a resting state of deep sleep, during which metabolic rate and body temperature drop considerably. It occurs only in certain mammals and one bird specles, the porwill, a North American relative of the nigtjiar.

B The phenomenon of hibernatin is one reason why the term homeothermy is going out of fashion, to be replaced by endothermy, because maintaining a stable body temperature is the very oposite of what hibermators do. Instead, body temperature flls, from around 38C, to about 19C above the extemal temperature, which is often close to 0C. At the same time, a hibermator's metabolie rate flls to as Itte as 1% of its normal value. The heartbeat becomes slow and iregular and breathing rate also slows.

C Hibernation is an active process, that ls, it is a state which animals enter into, not in response to immediate extermal conditions, but to internal stimull. Some species are remarkably precise and predictable. For example, the arctic ground squirel enters hibermation between 5 and 12 October. A feature of hibernation that distinguishes from other kinds of winter inactivity is that hibernators can arouse themselves spontaneously and are not dependent on external conditions, such as warm temperatures, to do s0. Brown and black bears, for example, are lethargic during very cold periods but are otherwise active in the winter. The arctic ground squirel emerges without fail between 20 and 22 April, regardless of the weather on those dates.

D True hibernation only occurs in relatively small mammals, though not all small mammals living in temperate habitats hibermate in winter, as we have seen. The largest mammal to hibernate is the marmot, which weighs about 5 kg. There are several reasons why larger mammals do not hibernate. Firstly, they would warm up too slowly and therefore use too much energy. Secondly, they have a smaller surface area to volume ratio and so can conserve body heat better than smaller species. Finally, they are better able to carry a thick coat and sufclent adipose tssue to last through the winter. Hibernators are mainly found in the orders Rodentia, Chiroptera and Insectivora. The hedgehog is an example of a hibemating insectivore.

E The physiological features that are characteristic of hibernation are not maintained throughout the winter. Rather, the animal wakes up at inervals, its temperature and metabolic rate increasing to near-normal levels. The function of this periodic arousal is not wholly clear. Some species, such as the chipmunks eat from stored food reserves during arousal perlods, but many others do not. Most specles urinate and defecate, mowe about and change their position, suggesting that arousal provides an opportunity for various essential physiological processes to be performed and to prevent the animal becoming moribund. From detailed measurements of Richardson's ground squirrel in the laboratory, it has been calculated that, during the rlaltively brief periods of arousal, an indvidual expends 83% of all the energy that it uses up during the entire hibernation period,

F Hibernation requires internal energy reserves in the form of adipose tissue and hibernators typically feed intensively prior to winter, building up their fat stores. Some species, such as the edible dormouse, switch to a carbohydrate-and lid-rich diet, eg.seeds, at this time. A characteristic of hibernating mammals is that they possess larger quanitities of a particular kind of adipose tssue called brown adipose tssue. Brown adipose tissue deposits are found around some internal organs and between the shoulder-blades of hibermators and their function is to generate body heat very rapidly,especally during periods of arousal.

G Hibemation might seem to be a safe, and rather agreeable way to spend the winter but, for some species, it is fraught with danger. For Belding's ground squrrels lving at high altitude in Tioga Pass, Callfornla, hibermation lasts 7-8 months. Two-thirds of all juveniles, hibernating for the frst time, and one-third of adult animals die during hibernation. Some die because their fat reserves run out before the end of hibematin; others are dug up and eaten by predators.

H Some mammals spend the winter. in groups, huddled together during periods of dormancy, and so consenve body heat, North American raccoons, for example, spend dormant periods in communal dens. Many specles of bats hibernate communally.

During hibernation, the body temperature of some bats can fall below 0C. In the autumn, they build up fat reserves that represent as much as a third of their total mass. For some mammals, hibernation is closely associated with olther important activities notably reproduction and dispersal. Consequently, energy reserves may have to support more than one activity For example, brown bears living at northern latitudes mate in the autumn and give bith to their cubs during winter lethargy. Edible domice and some bats mate immedlately after the end of hlberation. (In some species of bats, males wake up frst and mate with the females before they have woken up!).

Dispersal is the permanent departure of an individual from its place of birth, usually at the end of the breeding season. It is an important part of the life history of many animals, especally mammals, and tends to be sexually dimorphic, males dispersing further than females. Dispersal therefore requires intemal energy reserves in the form of fat, the very same reserves that they later need to survive the winter. There may thus be a trade-off in the lllallon of energy reserves to dlispersal and to hibernation.

13-17为匹配题

13. A risk of animals' hibemation during the winter G

14. The periodical actvities during the period of hibemation E

15. An example of an animal species prepare for hibernation F

16. A contast of hibermation and lethargy C

17. A reference to the place of hibernation in animals' life cycle H

18-21为匹配题

18. go through hibemation together to keep warm D

19. come out of hiberation on specific dates A

20. change its eating habits before hibermation C

21. reproduce during hibermation B

A. The arctic ground squrel