Science (086) — AI-generated practice question

Energy Loss: At each trophic level, only about 10% of the energy is transferred to the next level. The remaining 90% is lost as heat, used in digestion, and for daily activities. Since energy is non-recyclable and continuously lost, it diminishes as we move up the food chain.

Chemical Accumulation (Biological Magnification): Pesticides and harmful chemicals are non-biodegradable. They are absorbed by producers and, since they cannot be broken down, they accumulate in the body of each consumer. As one organism at a higher level eats many organisms from the lower level, the concentration of chemicals increases progressively. This is called biological magnification, with maximum concentration at the top trophic level.

Source: Chapter 13, Section 13.1.1 – Food Chains and Webs

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• The examiner expects you to contrast the 10% energy rule (energy loss) with the concept of non-biodegradability (chemical build-up). These are the two key reasons for opposite behaviour.
• Always use the term biological magnification — it is a defined term in the chapter and earns a dedicated mark.
• A common mistake is saying chemicals "increase" without explaining why — the reason is they are non-degradable and accumulate across multiple organisms consumed at each level.