Ch. 10

Question 1

Define thermoregulation

Answer 1

The maintenance of a relatively constant body temperature

Question 2

Define endotherm

Answer 2

An animal in which the body temperature is elevated by metabolically produced heat

Question 3

Define ectotherm

Answer 3

An animal in which the body temperature is determined by equilibration of the body with the thermal conditions in the environment (synonymous with poikilotherm)

Question 4

Define homeotherm

Answer 4

An animal that thermoregulates by physiological means

Question 5

Define heterotherm

Answer 5

An animal that holds different thermal relations from time to time or place to place

Question 6

Define temperature

Answer 6

Overall vibration of an object

Question 7

Define heat

Answer 7

Level of energy in an object

Question 8

Define conduction

Answer 8

The transfer of heat by intermolecular collisions through a material that is macroscopically motionless (i.e., solid to solid)

Question 9

Define convection

Answer 9

The transfer of heat by the mass flow of a material substance (i.e., gas to solid)

Question 10

Define evaporation

Answer 10

The transfer of heat from liquid vaporization

Question 11

Define thermal radiation

Answer 11

Transfer of heat by electromagnetic radiation between two surfaces that aren’t in contact

Question 12

Define compensation

Answer 12

The return of a physiological property toward its value that existed prior to an environmental change even though the animal remains in the changed environment

Question 13

Define countercurrent exchange

Question 14

Claude Bernard, a nineteenth century French physiologist often considered the father of modern animal physiology, is still remember today for a famous dictum: “Constancy of the internal environment is the condition for free life.” Does the study of thermal relations lend support to Bernard’s dictum?

Question 15

Suppose you have some lizards that are at 16°C and have been living at that temperature for 5 weeks. What is their resting metabolic rate? If the lizards are suddenly shifted to a room at 33°C, trace on the graph how their metabolic rate will change from the moment they are placed in the new room until 5 weeks have passed. Will they exhibit compensation?

Question 16

In the animal kingdom today, poikilotherms outnumber homeotherms by a great margin. Why is poikilothermy a successful way of life even though they sometimes must compete successfully with homeotherms to survive?

Question 17

In the rete mirabile serving the red swimming muscles of tunas, some key enzymes of foodstuff catabolism show gradients of concentration: They are more concentrated at the cold end of the rete and less concentrated at the warm end. These variations parallel variations that are often seen in the thermal acclimation of poikilotherms, when enzyme concentrations rise during acclimation to cold and fall during acclimation to heat. What do you think could be some of the reasons for these spatial and temporal variations in enzyme concentration? Why not have the highest observed enzyme concentrations everywhere at all times?

Question 18

Define regional homeothermy

Answer 18

Some regions of an individual’s body exhibit different thermal relations than other regions at the same time

Question 19

Define temporal homeothermy

Answer 19

An individual exhibits one type of thermal relation at certain times and another type at other times