Food chains rarely extend beyond four trophic levels. Which of the following best explains this? (A) Producer…

Question

Food chains rarely extend beyond four trophic levels. Which of the following best explains this?
(A) Producers can only support four types of consumers.
(B) Energy loss at each level means very little usable energy remains after four levels.
(C) Decomposers break down the food chain after the fourth level.
(D) Carnivores at the fourth level have no natural predators.

Accepted Answer

## Model Answer **(B) Energy loss at each level means very little usable energy remains after four levels.** Only 10% of energy transfers to the next trophic level; after four levels, usable energy becomes too little to sustain another level. Source: Chapter 13, Section 13.1.1 Food Chains and Webs ## Explanation The textbook explicitly states: *"The loss of energy at each step is so great that very little usable energy remains after four trophic levels."* The 10% law is the key concept here. Options A, C, and D are incorrect — the textbook never mentions producers limiting consumer *types*, decomposers stopping chains, or predator absence as the reason. Always link this answer to the **10% energy transfer rule**.

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