Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42.
Most desert animals will drink water if confronted with it, but many of them never have any opportunity. All living things must have water, or they will expire. The herbivores find it in desert plants. The carnivores slake their thirst with the flesh and blood of living prey. One of the most remarkable adjustments, however, has been made by the tiny kangaroo rat, who not only lives without drinking but subsists on a diet of dry seeds containing about 5% free water. Like other animals, he has the ability to manufacture water in his body by a metabolic conversion of carbohydrates. But he is notable for the parsimony with which he conserves his small supply by every possible means, expending only minuscule amounts in his excreta and through evaporation from his respiratory tract.
Investigation into how the kangaroo rat can live without drinking water has involved various experiments with these small animals. Could kangaroo rats somehow store water in their bodies and slowly utilize these resources in the long periods when no free water is available from dew or rain? The simplest way to settle this question was to determine the total water content in the animals to see if it decreases as they are kept for long periods on a dry diet. If they slowly use up their water, the body should become increasingly dehydrated, and if they begin with a store of water, this should be evident from an initial high water content. Results of such experiments with kangaroo rats on dry diets for more than 7 weeks showed that the rats maintained their body weight. There was no trend toward a decrease in water content during the long period of water deprivation. When the kangaroo rats were given free access to water, they did not drink water. They did nibble on small pieces of watermelon, but this did not change appreciably the water itent in their bodies, which remained at 66.3 % to 67.2 % during this period.
This is very close to the water content of dry-fed animals (66.5 %), and the availability of free water, therefore, did not lead to any “storage” that could be meaningful as a water reserve. This makes it reasonable to conclude that physiological storage of water is not a factor in the kangaroo rat’s ability to live on dry food.
Which of the following is NOT a source of water for the desert animals?
A. Desert plants
B. Metabolic conversion of carbohydrates in the body
C. The blood of other animals
D. Streams
Chọn đáp án D
Cái nào sau đây KHÔNG phải là nguồn nước cho các động vật ở sa mạc?
A. thực vật sa mạc
B. quá trình trao đổi carbohydrates trong cơ thể
C. máu của động vật khác
D. suối
Dẫn chứng: The herbivores find it in desert plants. The carnivores slake their thirst with the flesh and blood of living prey. One of the most remarkable adjustments, however, has been made by the tiny kangaroo rat, who not only lives without drinking but subsists on a diet of dry seeds containing about 5% free water. Like other animals, he has the ability to manufacture water in his body by a metabolic conversion of carbohydrates. (Động vật ăn cỏ tìm thấy nước từ trong thực vật của sa mạc. Loài ăn thịt thỏa mãn cơn khát của chúng bằng máu thịt của con mồi. Tuy nhiên, một trong những sự thích nghi đáng chú ý nhất nằm ở loài chuột túi nhỏ bé. Chúng không chỉ sống mà không cần uống nước. Chúng tồn tại bằng chế độ ăn với hạt khô chứa khoảng 5% nước. Giống như các loài động vật khác, chúng có khả năng sản sinh nước trong cơ thể bằng cách chuyển hóa carbohydrates.)