Surface area to volume ratio

• The larger the organism...

  The lower the SA:V ratio
• How does an organisms SA:V relate to their metabolic rate?

  The lower the SA:V, the lower the metabolic rate
• How doe s a large organism adapt to compensate for its small surface area to volume ratio?

  Develops a specialised gas exchange surface by increasing the SA (longer ears...)
• Why do multicellular organisms require specialised gas exchange surfaces?

  Small SA:V

  Larger diffusion distance

  Substances cannot easily enter the cells
• Three features of an effective gas exchange surface


  Large SA

  Thin

  Steep concentration gradient
• In large cells of single celled organisms, the mitochondria may be positioned close to the cell-surface membrane - why?

  Larger cells have a smaller SA:V

  Takes longer for oxygen to diffuse to mitochondria
• Explain the advantage for larger animals of having a specialise system that facilitate oxygen uptake

  Larger organisms have a smaller SA:V

  Faster diffusion since the diffusion pathway is shorter
• What environmental conditions results in adaptations in the system used for fish gills compared to the the human lungs

  • Water has a lower oxygen concentration than air
  • So having a system on the outside gives a large SA
• Why do shrews have smaller lung volumes than bats?

  Provides more oxygen for respiration
• Mammals such as a mouse and a horse are able to maintain a constant body temperature

  Explain the higher metabolic rate of a mouse compared to a horse

  Smaller SA:V

  More heat loss in relation to body size

  Faster rate of respiration
• For the rate of oxygen uptake, Why might a scientist use $\mu mol$


  Measures small uptake of oxygen
• Suggest one practical advantage of measuring masses of frog eggs, tadpoles and adults compared with measuring their volumes

  More accurate/less error in measuring mass
• Explain why oxygen uptake is a measure of metabolic rate in organisms

  Oxygen is used in respiration which provides energy/ATP
• Why can someone not make a comparison or conclusion?

  Missing information

  No statistical information - no statistical test conducted / measure of significant differences
• How might a worm exchange oxygen?

  Diffusion