Biomagnification refers to the process by which toxins or other harmful substances become more concentrated as they move up the food chain. It occurs when a substance enters an ecosystem and is taken up by small organisms, which are then consumed by larger organisms. Each time an organism is consumed, the substance is concentrated in the body of the larger organism, leading to higher and higher levels of the substance in the organisms at the top of the food chain.
For example, imagine a fictional substance called "X" is released into a lake. The "X" is taken up by small aquatic plants, which are then consumed by small fish. The small fish are then consumed by larger fish, and so on, up the food chain. By the time the substance reaches the top predator in the ecosystem, such as an eagle, the concentration of "X" is much higher than it was in the small aquatic plants at the bottom of the food chain.
The sentence "We learned that the solution to pollution is not dilution" relates to biomagnification because it highlights the idea that simply diluting a pollutant by spreading it out over a larger area does not necessarily make it less harmful. Instead, it may just lead to the pollutant being taken up by more organisms, leading to higher levels of the pollutant in the food chain, and potentially more harm to the ecosystem and the organisms living in it.