Energy Flow in Ecosystems
Trophic Levels and the 10% Rule
Learning Objectives
Identify the distinct trophic levels in an energy pyramid.
Apply the 10% rule to calculate energy availability at higher trophic levels.
Progress
3 sections
1
Energy Foundations
~10 minutesThe Source of All Energy
Energy enters most ecosystems as sunlight. Producers (autotrophs) capture this solar energy through photosynthesis, converting it into chemical energy stored in glucose ($ \ce{C6H12O6} $).
$$\ce{6CO2 + 6H2O ->[light] C6H12O6 + 6O2}$$
The chemical equation for photosynthesis
2
Visualizing the Pyramid
~15 minutesThe Energy Pyramid
A triangular diagram split into four horizontal sections: Producers at the base, Primary Consumers, Secondary Consumers, and Tertiary Consumers at the top....
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The 10% Rule
On average, only about 10% of the energy available within one trophic level is transferred to the next level. The remaining 90% is lost as heat or used for the organism's life processes.
3
Check Your Knowledge
Question 1
Place these organisms in the correct order of energy flow, starting from the energy source:
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Grasshopper (Primary Consumer)
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Shrew (Secondary Consumer)
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Sunlight
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Grass (Producer)
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Owl (Tertiary Consumer)
Drag items to reorder, then confirm
Question 2
If a producer level contains 5,000 Joules (J) of energy, how much energy is available to the secondary consumers?