Question

29. The water temperature in a lake varies between 4°C in the winter and 24°C in the summer. However, the metabolic rate of the fish in the lake is constant throughout the year. How might this happen? a. The fish lower their body temperature in the summer and raise it in the winter. b. The fish express isozymes that have different optimal temperature at different time of the year. c. The fish become less active in the winter to conserve energy. d. Activation of brown fat mitochondria increases metabolic activity in the winter. e. Metabolic activity in ectotherms are temperature independent.

30. When we are having a fever ― say 39°C, even though the body temperature is above normal temperature (37°C), we feel chilly and may even shiver. Why might this be? a. The temperature homeostatic mechanism begins to break down at 39°C. b. The homeostatic mechanism tries to chill the body back to 37°C. c. The homeostatic machinery is trying to bring body temperature to the new set point. d. The basal metabolic rate has increased. e. The chilliness and shivering are disease-related; they have nothing to do with thermoregulation.

Answer 1

29. Option C is correct - The fish become less active in the winter to conserve energy.

Explanation: As fish is an ectothermic animal, it cannot controls its body temperature. So in summer its metabolic activity increases and in winter its metabolic activity becomes lower and it becomes inactive. If the water becomes too cold, then  fish's metabolism will slow down, which leads to the fish becoming sluggish and sleepy.

30. Option C is correct -  The homeostatic machinery is trying to bring body temperature to the new set point.

Explanation: In fever, our thermo regulator, i.e hypothalamus set our body temperature above normal i.e.36.8⁰ C. So to raise the temperature to that newly set temperature, our muscles contracts to generate more heat. The higher body temperature may help fight infection by speeding white blood cell production and slowing bacteria reproduction.