Final answer:
The increase in concentration of DDT through trophic levels is an example of biomagnification. This process leads to higher concentrations of toxic substances in higher trophic level organisms, resulting in ecological consequences like fragile bird eggshells and population declines.
Step-by-step explanation:
The increase in concentration of the chemical pesticide, DDT, from the first trophic level to the fourth trophic level is an example of a pollutant that biologically accumulates or magnifies. This phenomenon is known as biomagnification, and it refers to the increasing concentration of persistent, toxic substances in organisms at each trophic level, from the primary producers to the apex consumers. Substances like DDT are fat-soluble, not water-soluble, and are stored in the fat reserves of organisms. As a result, predators at higher trophic levels, which eat many organisms containing these substances, end up with larger quantities in their bodies. This led to adverse effects in bird populations where DDT accumulation caused eggshell fragility, leading to increased egg breakage and population declines. The use of DDT was banned in the United States in the 1970s due to its harmful environmental impacts.