Question

1) Which of these factors should have the least effect on heat transfer in animals?

External insulation such as feathers or fur

Difference between body temperature and ambient temperature

Bone density

Body surface area

2) Which of the following is NOT a method used by ectotherms to regulate their body temperature?

Countercurrent heat exchange

Basking in the sun

Increasing metabolic rate

Shivering

Dilation or contraction of blood vessels

3) Which of these animals has the highest metabolic rate per unit body mass?

Horse

Cat

Elephant

Shrew

Answer 1

1. Bone density should have the least effect on heat transfer: Contrarily, external insulation (such as feathers or fur), the difference between body temperature and ambient temperature, and body surface area are important determinants of the rate of heat transfer between the body and the environment.
2. Ectotherms cannot increase their metabolic rate to regulate body temperature: By definition, ectotherms cannot metabolically produce body heat. Hence, while all other mechanisms such as countercurrent heat exchange, basking in the sun, shivering, and dilation or contraction of blood vessels are valid mechanisms, increment in metabolic rate is not.
3. Metabolic rate depends on the body surface area to volume ratio. Greater is this ratio, higher is the metabolic rate. Smaller bodies have higher surface area to volume ratio. Hence, shrew, being the smallest among the four given organisms, has the highest metabolic rate.