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Difficulty: MediumEnergy Flow, Food Chains, and Ecological Pyramids

In a freshwater pond ecosystem, energy flows sequentially through distinct trophic levels following the principle of ecological energy transfer. Consider the following aquatic organisms: Freshwater pike, Water fleas (Daphnia), Microscopic green algae (Chlorella), and Minnows.

Arrange these organisms in order from the HIGHEST available energy to the LOWEST available energy.

  1. 1Microscopic green algae (Chlorella)
  2. 2Water fleas (Daphnia)
  3. 3Minnows
  4. 4Freshwater pike

Answer

The correct order from highest available energy to lowest available energy is: Microscopic green algae (Chlorella) → Water fleas (Daphnia) → Minnows → Freshwater pike.
In any ecosystem, primary producers (green algae) fix solar energy into biochemical energy and possess the greatest amount of available energy. As energy transfers to primary consumers (water fleas), secondary consumers (minnows), and tertiary consumers (freshwater pike), roughly 90% of the energy at each level is dissipated as metabolic heat. Consequently, available energy decreases continuously from producers up to apex carnivores.

Step-by-Step Solution

1
Identify the trophic role of each organism in the pond ecosystem.
Microscopic green algae are primary producers (TL1), Water fleas are primary consumers (TL2), Minnows are secondary consumers (TL3), and Freshwater pike are tertiary consumers (TL4).
Determining trophic positions is necessary to trace the direction of energy transfer along the food chain.
2
Apply the 10% law of energy transfer (Lindeman's efficiency principle).
Energy decreases by approximately 90% at each successive trophic level due to metabolic respiration, movement, excretion, and heat dissipation.
The second law of thermodynamics requires that energy available to subsequent trophic levels decreases steadily from producers to top carnivores.
3
Arrange the organisms from maximum available energy (Trophic Level 1) to minimum available energy (Trophic Level 4).
Microscopic green algae (Chlorella) [TL1] → Water fleas (Daphnia) [TL2] → Minnows [TL3] → Freshwater pike [TL4].
Energy pyramids are strictly upright, meaning energy content is highest at the base and lowest at the apex.

Key Concept

Trophic Energy Transfer and the 10% Law
Estimated Time:1m 15s
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Topics

Energy Flow, Food Chains, and Ecological Pyramids

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