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  1. 1-biological-molecules

    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-cell-structure
    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
    7 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-exchange-and-transport
    3-1-adaptations-for-gas-exchange
    6 主题
  14. 3-2-human-gas-exchange
    10 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
    8 主题
  18. 3-6-mass-transport-in-plants
    6 主题
  19. 4-genetics-variation-and-interdependence
    4-1-dna-genes-and-chromosomes
    7 主题
  20. 4-2-dna-and-protein-synthesis
    6 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
  25. 5-energy-transfers-in-and-between-organisms-a-level-only
    5-1-photosynthesis-a-level-only
    5 主题
  26. 5-2-respiration-a-level-only
    7 主题
  27. 5-3-energy-and-ecosystems-a-level-only
    9 主题
  28. 5-4-nutrient-cycles-a-level-only
    4 主题
  29. 6-organisms-respond-to-changes-in-their-environments-a-level-only
    6-1-response-to-stimuli-a-level-only
    12 主题
  30. 6-2-nervous-coordination-a-level-only
    10 主题
  31. 6-3-skeletal-muscles-a-level-only
    6 主题
  32. 6-4-homeostasis-a-level-only
    11 主题
  33. 7-genetics-populations-evolution-and-ecosystems-a-level-only
    7-1-inheritance-a-level-only
    6 主题
  34. 7-2-populations-a-level-only
    3 主题
  35. 7-3-evolution-a-level-only
    5 主题
  36. 7-4-populations-in-ecosystems-a-level-only
    7 主题
  37. 8-the-control-of-gene-expression-a-level-only
    8-1-genetic-mutations-a-level-only
    2 主题
  38. 8-2-regulation-of-gene-expression-a-level-only
    11 主题
  39. 8-3-using-genome-projects-a-level-only
    4 主题
  40. 8-4-gene-technologies-a-level-only
    13 主题
  41. exam-guidance-and-skills
    essay-guidance
    3 主题
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Gross primary production

  • Gross primary production (GPP) can be defined as:

the chemical energy stored in plant biomass, in a given area or volume

  • Gross primary production in terrestrial plants can be expressed as:

    • energy per unit area, e.g. J m–2

    • mass per unit area, e.g. g m–2

      • biomass = stored chemical energy, so a measure of mass can be used to represent energy

  • Gross primary production in aquatic environments can be expressed as:

    • energy per unit volume, kJ m-3

    • mass per unit volume, e.g. kg m-3

Examiner Tips and Tricks

Remember that GPP is the stored chemical energy or biomass present in a given area or volume, so its units should include energy/mass, and area/volume.

If a unit also includes time, then this is a measure of productivity, which is not the same as production.

Calculating gross primary production

  • It is possible to calculate gross primary production and to determine the appropriate units

    • Remember that gross primary production is not a rate and so does not need to include time

Worked Example

The total biomass of the grass that grows in a 200 m2 field is found to be 1000 kg.

Calculate the gross primary production of the grass field. Give appropriate units.

Answer:

Step 1: calculate the biomass of grass in 1 m2 of the field

  • 1m2 is 1/200th of the field, so we divide the total field biomass by 200:

1000 ÷ 200 = 5 kg

Step 2: give the appropriate units

  • Primary production is a measure of biomass per unit area or volume, so in this instance our units must include a mass and an area

5 kg m-2

Worked Example

A patch of rainforest covering an area of 1 km2 is estimated to contain 1500 kg of biomass.

Calculate the gross primary production of this rainforest patch. Give your answer in g m-2.

Answer:

Step 1: calculate the biomass of 1 m2 of the rainforest patch

  • 1 km2 = 1000 x 1000 = 1 000 000 m2

1500 ÷ 1 000 000 = 0.0015 kg

Step 2: convert this into grams

  • 1 kg = 1000 g

0.0015 × 1 000 = 1.5 g m-2

Worked Example

The biomass of aquatic algae in a tank is estimated to contain a total of 5440 joules of chemical energy. The tank has a volume of 4 m3.

Calculate the gross primary production of this aquatic algae. Give appropriate units.

Answer:

Step 1: calculate the chemical energy of the aquatic algae in 1 m3

5440 ÷ 4 = 1360 J

Step 2: give the appropriate units

  • Note that we are dealing with aquatic plants, so the units will be volume rather than area

1360 J m-3 OR 1.36 kJ m-3