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Biology AS AQA

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  1. 1-1-biological-molecules-carbohydrates
    11 主题
  2. 1-2-biological-molecules-lipids
    3 主题
  3. 1-3-biological-molecules-proteins
    5 主题
  4. 1-4-proteins-enzymes
    12 主题
  5. 1-5-nucleic-acids-structure-and-dna-replication
    8 主题
  6. 1-6-atp-water-and-inorganic-ions
    4 主题
  7. 2-1-cell-structure
    7 主题
  8. 2-2-the-microscope-in-cell-studies
    4 主题
  9. 2-3-cell-division-in-eukaryotic-and-prokaryotic-cells
    8 主题
  10. 2-4-cell-membranes-and-transport
    9 主题
  11. 2-5-cell-recognition-and-the-immune-system
    7 主题
  12. 2-6-vaccines-disease-and-monoclonal-antibodies
    6 主题
  13. 3-1-adaptations-for-gas-exchange
    6 主题
  14. 3-2-human-gas-exchange
    14 主题
  15. 3-3-digestion-and-absorption
    5 主题
  16. 3-4-mass-transport-in-animals
    6 主题
  17. 3-5-the-circulatory-system-in-animals
    4 主题
  18. 3-6-mass-transport-in-plants
    6 主题
  19. 4-1-dna-genes-and-chromosomes
    10 主题
  20. 4-2-dna-and-protein-synthesis
    3 主题
  21. 4-3-genetic-diversity-mutations-and-meiosis
    7 主题
  22. 4-4-genetic-diversity-and-adaptation
    6 主题
  23. 4-5-species-and-taxonomy
    4 主题
  24. 4-6-biodiversity
    9 主题
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Exam code:7401

Surface area to volume ratio & metabolic rate

  • The surface area to volume ratio of an organism is related to its metabolic rate

    • The metabolic rate of an organism is the energy expended by that organism within a given period of time

  • This relationship exists because of the relationship between surface area to volume ratio and heat loss

    • Heat is lost to the environment at the body’s surface, so having a large body surface in relation to volume will allow more heat to be lost

    • This means that:

      • small animals, with a higher SA:V ratio, will lose more heat to their surroundings, meaning that they need a relatively high metabolic rate to maintain body temperature

      • large animals, with a lower SA:V ratio, will lose less heat, meaning that they can maintain body temperature at a relatively low metabolic rate

Graph showing basal metabolic rate vs. mass for animals including shrew, mouse, sheep, and elephant. Rate decreases as mass increases.
Basal metabolic rate decreases as mass increases

Examiner Tips and Tricks

As ever, be careful not to confuse surface area with SA:V ratio. Smaller animals have a smaller surface area than larger animals, but they have a higher SA:V ratio.

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