BIO 109 Home
Questions | Answers

1. Too hot and proteins break down. Too cold and body functions don't work as well.

2. Every 10 degrees C rise in temperature results in a doubling of the rate of biochemical reactions (metabolism), up to a point. It is important because how quickly an organism functions (digests, moves, thinks, etc.) depends on its rate of metabolism which depends on its body temperature. Also higher rates of metabolism require more energy and water.

3. Radiation: heat gain/loss because essentially all objects give off heat so every object is losing heat from itself and gaining heat from other objects (e.g., the sun, a rock, etc.).
Convection: heat gain/loss by moving air (wind) or water.
Conduction: heat gain/loss between touching objects.
Metabolism: heat gain due to biochemical reactions produced in the body (e.g., muscle contraction).
Evaporation: heat loss due to the conversion of water from liquid to gas.

4. Ectotherms: principal source of body heat is from the environment. All but mammals and birds.
Endotherms: principal source of body heat is internally, from metabolism. Mammals and birds.

5. Using posture, orientation, and microclimate selection (e.g., burrow) to regulate body temperature.

6. Altering metabolic generation of body heat to regulate body temperature.

7. Ectothermy: Advantage: uses 10X less energy.
Disadvantage: must be cold and slow when lack environmental source of heat.
Endothermy: Advantage: always ready to go (don't have to depend on environment for heat).
Disadvantage: uses 10X more energy.

8. Less insulation = faster rate
Higher Temperature difference between body and environment (temperature gradient) = faster rate
Higher Surface area to volume ratio = faster rate

9. Mouse. So the mouse loses heat faster so must eat more food per pound of body weight.

10. A lowering of the body temperature below activity temperature.

i. Daily torpor in response to cold [= daily torpor in response to cold]
ii. Hibernation [= seasonal torpor in response to cold]
iii. Daily estivation [= daily torpor in response to heat/dryness]
iv. Seasonal estivation [= seasonal torpor in response to heat/dryness]

i. Saves energy by lowering the rate of heat loss from the body by lowering the difference in temperature between the body and environment.
ii. Saves energy by lowering metabolism as body temperature cools
iii. Saves water by lowering evaporation rates as surface of body cools
iv. Saves water by lowering production of urine and feces because as metabolism slows, less wastes are produced
v. Saves water by lowering breathing rate as tissues demand less oxygen and produce less carbon dioxide; also reduces amount of water lost in each breath because animal is breathing out cooler air which holds less water.

13. Endure, Evade, Expire

14. Outline for Enduring

  • Temperature Stress
    • Reduce Heat Input: spines for insulation
    • Dissipate Heat: long extremities
    • Tolerate Hyperthermia: C4 Photosynthesis
  • Water Stress
    • Water Conservation
      • Decrease Cutaneous Water Loss: use waxes in outer covering.
      • Decrease Excretory Water Loss: produce uric acid
      • Decrease Respiratory Water Loss: drought deciduous
    • Tolerate Dehydration: A saguaro can tolerate an 80% reduction in water from the body.

15. Water Storage: succulence, fat storage
Spatial: migration, microclimate selection
Temporal: nocturnal, torpor

16. Uric acid uses 10X less water, but costs additional energy. Birds, snakes, lizards, some insects do this.