This field study is about temperature regulation in desert mammals. Fig. 1 shows the outer surface of a fennec fox ear with many blood vessels close to the ...
Question 1 Report
This field study is about temperature regulation in desert mammals. Fig. 1 shows the outer surface of a fennec fox ear with many blood vessels close to the skin. The fox was observed at a conservation centre on days with different air temperatures. Blood flowing through vessels near the surface can transfer thermal energy to the surroundings. The body must keep the temperature of its cells within a narrow range so that enzymes work effectively. Table 1 shows measurements taken while the fox was resting in shade.
| Air temperature / degrees C | Ear surface temperature / degrees C | Blood flow in ear vessels / arbitrary units |
|---|---|---|
| 18 | 24 | 3 |
| 28 | 32 | 6 |
| 38 | 40 | 10 |
(a) What is the name of the process that keeps body conditions stable? [1]
(b) Describe the change in blood flow in ear vessels as air temperature rises. [1]
(c) Give the increase in ear surface temperature between 18 degrees C and 38 degrees C. [1]
(d) Explain how increased blood flow near the ear surface can cool the fox. [3]
(e) Draw arrows on Fig. 1 to show heat moving from blood vessels to the air. [1]
(f) When air temperature is low, what happens to the diameter of skin arterioles? [1]
(g) Give one response, other than changing blood flow, that a mammal can use when it is too hot. [1]
(h) Complete this sentence: an increase in skin blood flow is called vasodilation of the __________. [1]
Answer Details
- (a) The process maintaining stable body conditions is homeostasis. [1]
- (b) Blood flow in the ear vessels increases as air temperature rises, from 3 to 10 arbitrary units. [1]
- (c) Increase in ear surface temperature \(=40-24=16\degree\text{C}\). [1]
- (d) Increased blood flow brings more warm blood close to the ear skin surface. Heat transfers from the blood to the cooler surrounding air, preventing body temperature from rising too much. [3]
- (e) The arrows show heat moving from blood vessels, through the skin, to the surrounding air. [1]
- (f) In low air temperature, skin arterioles constrict and become narrower. [1]
- (g) A mammal may sweat, pant, rest in shade, or reduce activity when too hot. [1]
- (h) Increased skin blood flow is vasodilation of the arterioles. [1]
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