Final answer:
Biomagnification is the process of toxic substances increasing in concentration as they move up the trophic levels.
Step-by-step explanation:
Biomagnification is the process whereby toxic substances, such as DDT, increase in concentration as they move up the trophic levels in food chains or food webs. This occurs because organisms at higher trophic levels consume many organisms from lower trophic levels, causing the toxic substances to accumulate in their bodies. A classic example is the accumulation of DDT in birds, especially apex consumers like bald eagles, which can lead to negative effects on their reproduction, such as fragile eggshells.