Which of the following best describes bioaccumulation?

• A. The dispersion of pollutants in air
• B. The accumulation of substances in an organism over time
• C. The chemical degradation of toxins in water
• D. The decrease of contaminants in an organism over time

Answer: (B)

Bioaccumulation is the buildup of a substance in an individual organism over time, because it is taken in faster than it can be eliminated. This means the organism accumulates higher internal concentrations than are present in its surroundings. The description that fits this best is the accumulation of substances in an organism over time. The other ideas describe pollutants dispersing through air, toxins being degraded in water, or contaminants decreasing in an organism, none of which capture the idea of substances piling up inside an organism. (Note: when this buildup occurs across many organisms, it can lead to higher concentrations up the food chain, a pattern called biomagnification.)