2.3 Metabolic rate

• Describe the term metabolic rate.


  The quantity of energy consumed by an organism per unit time (e.g kg per day)
• List the different ways metabolic rate can be measured.

  Respirometers

  Oxygen probes

  Carbon dioxide probes

  Calorimeters
• State the different specialised transport systems that exist in invertebrates.

  Single circulatory system

  Incomplete double circulatory system

  Complete double circulatory system
• Describe a single circulatory system.

  Fish have a single circulatory system consisting of one atrium and one ventricle.

  -This is an inefficient system as high pressure blood flows to the gills to become oxygenated before passing to capillary beds of the body as low pressure blood.
• Describe an incomplete double circulatory system.


  Amphibians and most reptiles have an incomplete double circulatory system consisting of two atria and one ventricle.

  -circuit is incomplete as oxygenated and deoxygenated blood mix in the one ventricle.
• Describe a complete double circulatory system.

  Birds and mammals have a complete double circulatory system consisting of two atria and two ventricles. (4 chamber heart)

  -Complete double circulatory systems enable higher metabolic rates to be maintained. There is no mixing of oxygenated blood and deoxygenated blood and the oxygenated blood can be pumped out at a higher pressure. This enables more efficient Oxygen delivery to cells.
• Explain why the control experiment for using respirometers should contain no living organism.

  To prove that the organism is consuming the Oxygen.