Which statement best describes bioaccumulation and biomagnification?

• A. Bioaccumulation is the buildup of a substance in an organism over time; biomagnification is the increasing concentration of a substance up the food chain.
• B. Bioaccumulation is the increasing concentration up the food chain; biomagnification is the buildup in a single organism.
• C. Bioaccumulation refers to harmful effects; biomagnification refers to beneficial nutrients.
• D. Bioaccumulation occurs in water; biomagnification occurs in air.

Answer: (A)

This question tests how contaminants behave in organisms versus across food webs. Bioaccumulation means a substance builds up in a single organism over time because it is taken in faster than it is eliminated (through water, food, or sediment exposure and limited metabolism). Biomagnification means the same substance becomes more concentrated as you move up the food chain, because predators accumulate not just what they eat, but the contaminants stored in multiple prey items, leading to higher levels in top predators.

Why the best description fits: a persistent, lipophilic contaminant tends to stay in fatty tissues and is not readily excreted, so it accumulates in an individual (bioaccumulation). When that contaminant is passed along through prey, each higher trophic level concentrates more of it, so concentrations increase up the food chain (biomagnification). This distinction is important because a chemical can accumulate within an organism and also become magnified in predators, but the mechanisms and implications differ.

For context, a classic example is DDT-like substances: small organisms accumulate them, fish accumulate higher levels, and birds of prey end up with very high concentrations, which can cause reproductive harm.

The other statements don’t fit because they swap the definitions, equate the terms with harmful effects versus nutrients, or limit the concept to a single medium like water or air rather than describing the relationship between accumulation in individuals and amplification through the food chain.