What is biological magnification? Explain why top predators (including humans) are most at risk from pesticide poisoning, while plants and water show much lower concentrations.

Question

Accepted Answer

BIOLOGICAL MAGNIFICATION (also called BIOACCUMULATION or BIOMAGNIFICATION): The process by which CONCENTRATION of TOXIC, NON-BIODEGRADABLE substances INCREASES progressively at each trophic level in a food chain. It occurs because these substances are not broken down or excreted — they accumulate in the body tissues (especially fat) of organisms. EXAMPLE WITH DDT: DDT (a pesticide) was widely used and entered water bodies through runoff. Water: 0.003 ppb (very small amount). Phytoplankton (absorb and retain DDT): ~0.04 ppb. Small fish (eat millions of phytoplankton): ~0.5 ppb. Large fish (eat many small fish): ~2 ppm. Fish-eating birds (osprey, eagles): ~25 ppm — nearly 10 MILLION times higher than in water. WHY TOP PREDATORS ARE MOST AT RISK: A large fish must eat MANY small fish to survive. Each small fish contains accumulated DDT. The large fish retains ALL that DDT. A fish-eating bird eats MANY large fish, retaining even more. At each step, the AMOUNT OF FOOD consumed is large, but the DDT is NOT excreted. It stays in fatty tissues and builds up. HUMAN RELEVANCE: Humans eating fish (especially large marine fish like tuna, swordfish) can accumulate significant mercury, PCBs, and other persistent chemicals. This is why pregnant women are often advised to limit large fish consumption — these chemicals can harm foetal development.

Practice — Our Environment — Ecosystems, Food Chains and Waste

Sign in to save attempts to your dashboard and track your accuracy over time

Find a verified tutor

Join a live course

Browse coaching centres

About

Categories

Support

Documentation

Get Study Tips & Updates

Download Our App

Download for iOS

Download for Android

Popular Cities