A duck has a thick layer of fat just beneath its skin. In addition to making the

Question

A duck has a thick layer of fat just beneath its skin. In addition to making the duck more buoyant, this fat helps it stay warm in cold water. a. Why does the duck have trouble maintaining its body temperature in cold weather? b. Why does the duck have more trouble staying warm in cold water than in cold air? c. How does the layer of fat help the duck keep warm? d. Fat is relatively rigid but is chemically almost indistinguishable from liquid oil. Why wouldn’t liquid oil be as effective as semi-rigid fat at keeping the duck warm? e. Muscle tissue is also relatively rigid, but having an extra layer of muscle wouldn’t be as effective at keeping the duck warm as the layer of fat. Why not? f. The duck’s oily feathers also tend to trap air near its skin so that cold water doesn’t actually touch the duck’s skin. Why does this trapped air help keep the duck warm?

Explanation / Answer

A&B) The duck maintains the body temperature through a mechanism called counter current exchange.

Arterial blood leaves the ducks upper body at a warm body temperature, while venous blood in the duck’s foot is quite cool. As cold blood runs up the leg from the foot and passes by the arteries, it picks up most of the heat from the arteries. As it travels, the blood flowing down is cooled, and the blood flowing up is warmed. Thus, by the time arterial blood reaches the foot, it is cool and does not lose too much heat in the cold water, and venous blood reaching the upper body has already been warmed, helping maintain upper body heat.

C) The thick layer of fat serves as an insulator for the ducks body.

D) Liquid oil will not be a convenient option for storage under the skin

E) The extra layer of muscle will not serve as an insulator as fat does.

F) Feathers trap tiny pockets of air next to the bird and the bird warms those pockets of air and hold that warm air around itself, thereby preventing cold air from touching its skin. The more air trapped, the warmer the bird.

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