The term for the gradual increase of a substance within an organism over time is called bioaccumulation. This process occurs when an organism absorbs a toxic substance, such as heavy metals or persistent organic pollutants, faster than it can eliminate it. Bioaccumulation leads to higher concentrations of these substances in the organism compared to the surrounding environment. Over time, this accumulation can result in biomagnification as predators consume prey that have already accumulated toxins, impacting the entire food chain. Understanding bioaccumulation is crucial for assessing ecological and human health risks associated with environmental pollutants.