What typically causes biological magnification?

Biological magnification occurs when toxic substances accumulate in living organisms and increase in concentration as they move up the food chain. This process primarily involves pollutants or toxins that can be persistent in the environment, such as mercury or certain pesticides. When these substances are introduced into an ecosystem, they are often absorbed by organisms at the bottom of the food chain—like small fish or plant life—where their concentrations can become elevated. As larger animals consume these smaller organisms, the toxins not only bioaccumulate in their bodies but also become magnified in concentration as each subsequent predator consumes more prey that contains these harmful substances. Thus, biological magnification is directly linked to the presence and persistence of toxins in the environment, leading to higher and more dangerous concentrations in top predators, including humans. The other options do not directly lead to this phenomenon: increased food availability might change population dynamics but not toxin concentrations, natural selection pertains to the survival of species rather than toxin accumulation, and genetic diversity relates to the variety of genes within a species, which does not influence toxin levels.