Chapter 8, Problem 48A

Summary Introduction

To explain:

The way by which certain toxins such as PCBs increase in concentration in trophic levels.

Introduction:

Pollution and changes in atmosphere are a big threat to biodiversity and global stability. Pollution changes composition of air, soil and water. Many man- made chemicals are also released into the environment. Pesticides such as DDT and industrial chemicals such as PCBs are harmful toxins that have been found in food webs.

Answer to Problem 48A

The concentration of toxic substances such as PCBs increases as the trophic level in a food chain or food web increases due to biological magnification.

For example if water is polluted with PCBs, planktons living in this water gets the toxic PCB in their tissues. When they are eaten by small fish the concentration of PCBs in fish is more than it was in plankton. Now if these small fish are eaten by birds, the concentration of toxic PCB will be amplified because one bird will feed on hundreds of fish and a small level of PCB in plankton gets magnified in a single fish which feeds on hundreds of plankton. So from a small concentration of toxic chemical in water, the concentration increased with each trophic level.

Explanation of Solution

Toxic substances are ingested by organisms when they drink contaminated water or eat other organisms that contain toxic chemicals. These chemicals get accumulated in the tissues of the organisms. Carnivores at the higher trophic levels are most affected by the accumulation because of the process of biological magnification.

Biological magnification is the increasing concentration of toxic substances in organisms as trophic levels increase in a food chain or food web. The concentration of toxic substance is low when it enters the food chain/ food web. As it spreads to higher levels, the concentration of toxic substance in individual organism increases. These substances might disrupt the normal processes in some organisms.