Chapter 24

Ecosystem Dynamics

24.1 Lesson 24.1: Flow of Energy

Lesson Objectives

• Explain where all the energy in an ecosystem ultimately comes from.


• Classify organisms on the basis of how they obtain energy (producers, consumers, and
  decomposers) and describe examples of each.


• Be able to draw and interpret a food web.


• Explain the flow of energy through an ecosystem using an energy pyramid.

Check Your Understanding

• What is photosynthesis?


• What are some examples of organisms that can photosynthesize?


• What is a community?

Introduction

Energy is defined as the ability to do work. In organisms, this work can involve not only
physical work like walking or jumping, but also carrying out the essential chemical reactions
of our bodies. Therefore, all organisms need a supply of energy to stay alive. Some organisms
can capture the energy of the sun, while others obtain energy from the bodies of other
organisms. Through predator-prey relationships, the energy of one organism is passed on to
another. Therefore, energy is constantly flowing through a community. Understanding how
this energy moves through the ecosystem is an important part of the study of ecology.