Q1. [1] medium initial-understanding
Which of the following correctly explains why harmful chemicals like pesticides are found in the highest concentration in organisms at the top of a food chain?
(A) Top-level consumers eat the most food, so they ingest more pesticides directly from the soil.
(B) Pesticides are produced naturally by large carnivores as a by-product of digestion.
(C) Non-degradable chemicals are not excreted and keep accumulating at each successive trophic level, reaching the highest concentration in top consumers.
(D) Pesticides evaporate from lower trophic levels and are absorbed through the skin of top-level consumers.
- A Top-level consumers eat the most food, so they ingest more pesticides directly from the soil.
- B Pesticides are produced naturally by large carnivores as a by-product of digestion.
- C Non-degradable chemicals accumulate progressively at each trophic level, so the final consumer inherits the combined load from all levels below.
- D Pesticides evaporate from lower trophic levels and are inhaled by top-level consumers.
Generated by claude-sonnet-4-6 · 2026-06-26 00:58 · grounding rag
Model Answer
(C) Non-degradable chemicals accumulate progressively at each trophic level, so the final consumer inherits the combined load from all levels below.
Explanation
The textbook (Ch. 13) explicitly states that pesticides "are not degradable" and therefore "get accumulated progressively at each trophic level," with the maximum concentration reaching top consumers — this phenomenon is called biological magnification. Options A, B, and D are factually incorrect as per the chapter.