Kean University Continuing Education

Implementing the Science Standards K-4


Pyramid of Energy in Ecology

Introduction

We can consider a typical food chain in the environment. It can be written as follows.

In this food chain each component has a definite function.

The Pyramid of Energy in Ecology

The food chain described above can be represented using a pyramid.

The four levels of the pyramid are the Primary Producers, the Primary Consumers, the Secondary Consumers and the Tertiary Consumers. Notice that each level is smaller than it would be in a normal pyramid. This indicates that the population size gets smaller as you go up the pyramid.

Concentration and Transmission of Environmental Toxins via the Food Pyramid

Many toxins in the environment are concentrated in the food pyramid and transmitted upwards through the food pyramid. This is due to the fact that these toxins are not biodegradable. A biodegradable chemical substance can be broken down by the metabolic action of bacteria and fungi in the soil and water. Toxins are not biodegradable so they maintain the poisonous effects as they are being passed through the food chain.

An exercise to do with students is to estimate how much toxin a snake will have in its body if each plant has one unit of toxin and the toxins are amplified 100 times in each level.

This concentration and amplification of toxins in the food chain was responsible for nearly wiping out the American Bald Eagle in the United States during the last half of the 20th century. Widespread, non-point source use of the pesticide DDT resulted in concentration and amplification of DDT in the food chain. DDT in the Eagle prevented their eggs from hatching properly. The Eagle was saved by environmental laws passed by the Congress in the 1970s.