What best describes bioaccumulation?

• A. Toxins build up in a single organism over time
• B. Toxins vanish after one generation
• C. Toxins cannot accumulate in organisms
• D. Toxins only accumulate in soils

Answer: (A)

Bioaccumulation is the buildup of a toxin inside a single organism over time. When an organism takes in a contaminant from its environment or diet faster than it can eliminate it, the chemical concentrates in its tissues and increases as the organism lives. This is often seen with persistent, fat‑soluble substances, so animals can end up with higher internal levels even if environmental concentrations are low. This concept is different from the toxin simply disappearing after one generation or never accumulating at all, and it’s not limited to soils—it's about the increasing concentration inside the organism itself. For example, mercury can accumulate in fish as they live longer, leading to higher levels in their tissues.