更多"Thermoregulation Mammals and birds"的相关试题:
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Thermoregulation
Mammals and birds generally maintain body temperature within a narrow range (36-38~C for most mammals and 39-42℃ for most birds) that is usually considerably warmer than the environment. Because heat always flows from a warm object to cooler surroundings, birds and mammals must counteract the constant heat loss. This maintenance of warm body temperature depends on several key adaptations. The most basic mechanism is the high metabolic rate of endothermy itself. Endotherms can produce large amounts of metabolic heat that replace the flow of heat to the environment, and they can vary heat production to match changing rates of heat loss.
Heat production is increased by such muscle activity as moving or shivering. In some mammals, certain hormones can cause
mitochondria to increase their metabolic activity and produce heat instead of
ATP. This
nonshivering thermogenes
A. Heat loss that must be reversed.
B. The adaptation of brown fat tissue in the neck.
C. The maintenance of healthy environmental conditions.
D. Conditions that affect the metabolism.
[填空题]Birds, flowers, mammals.
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The Evolution of Birds
Birds Began as Feathered Reptiles Birds evolved during the great reptilian radiation of the Mesozoic era. Amniotic eggs and scales on the legs are just two of the reptilian features we see in birds. But modern birds look quite different from modern reptiles because of their feathers and other distinctive flight equipment.
Characteristics of Birds Almost every part of a typical bird’s anatomy is
modified in some way that enhances flight. The bones have an internal structure that is honeycombed, making them strong but light. The skeleton of a frigate bird, for instance, has a wingspan of more than 2 meters but weighs only about 113 grams. Another adaptation reducing the weight of birds is the absence of some organs. Females, for instance, have only one ovary. Also, modern birds are toothless, an adaptation that trims the weight of the head. Food is not
A. simple
B. quiet
C. sad
D. short