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Biology Unit 4
Topic 5: On the wild side
7. Carry out calculations of net primary productivity
and explain the relationship between gross primary
productivity, net primary productivity and plant
The rate at which energy is incorporated into organic molecules in the plants in photosynthesis is
called gross primary productivity (GPP). Plants use some of the organic molecules in respiration.
The rate at which energy is transferred into new plant biomass that can be eaten by herbivores or
decomposers is the net primary productivity (NPP). This is the energy stored in their body tissues
the net amount left after the cost of respiration is included.
The relationship between them is:
NPP = GPP R
If you combine the NPP of each biome (type of ecosystem) with the area of the Earth it covers, you
can calculate how much each biome contributes to the NPP of the earth.
Text Book: p. 34 - 35