Final answer:
Biomagnification leads to the buildup of toxins in all organisms in a food chain; however, it causes the most toxin buildup in organisms at the top of the food chain - the apex or tertiary consumers, such as tuna.
Step-by-step explanation:
Biomagnification refers to the increasing concentration of toxic substances in organisms at each higher level in a food chain, from the primary producers to the apex consumers. In this process, toxins such as polychlorinated biphenyls (PCBs) or heavy metals like mercury, lead, and cadmium can accrue in increasingly larger concentrations as you move up the food chain. Primary producers, like seaweed or any photoautotroph, absorb these toxins directly from the environment.
They are then eaten by primary consumers (like urchins), which then are consumed by secondary consumers (like sculpins), and eventually by tertiary consumers (like tuna), also known as apex consumers. With each step in this food chain, the concentration of these toxins in each organism can be significantly greater than in the organism from the previous trophic level. This happens because each consumer is eating many organisms from the level below and thus accumulating all of the toxin contained in those organisms.
Therefore, the correct answer to your question is a. Tuna (tertiary consumer). Apex or tertiary consumers, like tuna, tend to have the highest levels of toxins built up in their bodies through biomagnification because they are at the top of the food chain.
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