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Biology Unit 4
Topic 5: On the wild side
8. Calculate the efficiency of energy transfers
between trophic levels.
What is a trophic level?
It's a feeding level, as often represented in a food chain or web eg. A primary producer is always at
the bottom trophic level, followed by primary consumers, etc.
As energy passes from trophic level to trophic level, only a fraction is transferred (1- 15%, averaging
around 10%). Consequently, the numbers and biomass of organisms decrease ad you ascend a food
Calculating efficiency of energy flow from one trophic level to the next
Producer to primary consumer. First we find out how much energy is available to primary
GPP R = NPP 44 090 20 000 = 24 090 kJ m¯² year¯¹
Efficiency of transfer =
Text Book: p. 36 - 37