AQA A Level Biology复习笔记3.1.4 SA:V Ratio & Metabolic Rate

• The metabolic rate of an organism is the amount of energy expended by that organism within a given period of time
• The basal metabolic rate (BMR) is the metabolic rate of an organism when at rest. The BMR is significantly lower than when an organism is actively moving
• During periods of rest, the body of an organism only requires energy for the functioning of vital organs such as the lungs, heart and brain
• The metabolic rate of an organism can be measured/estimate using different methods:
  • Oxygen consumption
  • Carbon dioxide production
  • Heat production

   

Metabolic rate increases with body mass

Body Mass

• Experiments conducted by scientists have shown that the greater the mass of an organism, the higher the metabolic rate
  • Therefore, a single rhino consumes more oxygen within a given period of time compared to a single mouse

   

SA:V Ratio

• Although metabolic rate increases with body mass the BMR per unit of body mass is higher in smaller animals than in larger animals
  • Smaller animals have a greater SA:V ratio so they lose more heat, meaning they have to use up more energy to maintain their body temperature

   

• Different apparatus can be used for investigating metabolic rates in organisms:
  • Respirometers
  • Oxygen/carbon dioxide probes
  • Calorimeters