OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is the process of bioaccumulation?

1. The rapid growth of algae in water bodies

2. The accumulation of chemicals in small quantities that become toxic

3. The natural breakdown of nutrients in soil

4. The loss of biodiversity in ecosystems

The correct answer is: The accumulation of chemicals in small quantities that become toxic

Bioaccumulation refers to the process by which certain substances, typically toxins or chemicals, accumulate in the tissues of living organisms over time, often in small quantities. When these substances are ingested or absorbed—whether through food, water, or the environment—they can build up faster than the organism can metabolize or excrete them. This accumulation can lead to harmful concentrations of these chemicals, which, even in small doses, can become toxic. Bioaccumulation is particularly concerning in food webs, as organisms at higher trophic levels, like predators, can accumulate even greater concentrations of these toxins through their diet, a phenomenon known as biomagnification. This concept is crucial for understanding environmental health and safety, as it highlights how pollutants can threaten not only individual species but entire ecosystems. The other options, while related to ecological concepts, do not accurately define bioaccumulation. For instance, the rapid growth of algae refers to algal blooms, often related to nutrient run-off. The natural breakdown of nutrients is more about nutrient cycling, which is essential for ecosystem functioning. Loss of biodiversity encompasses a broader range of ecological changes that do not specifically address the accumulation of chemicals in organisms.