Life Functions and Energy Intake

Chapter 2

All living things require energy to do work. Plants get the energy they need by producing their own food. Other organisms get the food they need by eating other organisms, including plants.

Plants make their own food in a process called photosynthesis. The prefix “photo” means “light,” and the base word “syn” means “together.” During photosynthesis, carbon dioxide and water react in the presence of light energy from the Sun. The reaction produces food in the form of a sugar. It also releases oxygen as a waste product.

Organisms that eat other organisms to get the energy they need must digest their food. Digestion is the process of breaking down food into its simplest parts, or molecules. The body breaks down molecules in the presence of oxygen to release the energy locked in the molecules’ chemical bonds. This process, called respiration, is the opposite of photosynthesis.

Some organisms live in environments where oxygen is unavailable, making respiration impossible. Instead, these organisms depend on the process of fermentation to get the energy they need for work.

In this chapter you will learn about:

Goal Setting

You may already know a great deal about the processes of photosynthesis, respiration, and fermentation. There may also be more you want to know. Think about some questions you already have about these processes.

Record them in the chart below. Then, as you read, return to the chart. Write the answers to your questions. As you read and learn, you may find that you have additional questions.

Return to this chart as often as you like. Record your questions and then return to write the answers when you know them.

Questions Answers