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How Enlightening

Aspen Photos courtesy Lindsay Whitaker

What is a tree made of?

Where do the matter and energy in a tree come from?

As you studied Earth's living systems you have certainly learned about food chains through which matter and energy move. Click here to review ideas about food chains. Early in the school years, students learn that a plant needs light and water to grow. Most students might even be able to tell you that plants take in carbon dioxide and give off oxygen, which animals then breathe.

This lesson will attempt to help you understand what happens to matter and energy as they are stored in living systems.

Look around and find something made of wood. Wood is one example of the substances that plants can produce. A tiny seed can grow to be a large tree by producing structures from wood. Most of the matter in wood and most other materials in plants begins as carbon dioxide in the atmosphere and water in the soil. Let's trace the flow of matter and energy in plants.

Aspen Photos courtesy Lindsay Whitaker

Look closely at the diagram above. Notice that sunlight strikes the chlorophyll and is captured in the leaves. The energy from the sunlight is used to create chemical bonds to hold the glucose molecules together. In this way the sun's energy is stored as chemical energy. If the chemical bonds holding glucose together are broken, the energy will be released.

The matter to form glucose comes from carbon dioxide and the hydrogen in water. The oxygen from water is released into the atmosphere. Glucose and other molecules produced in this process called photosynthesis are used to create the structures of plants. Do you know what makes up a tree? If you said, "Sunlight, matter from carbon dioxide and hydrogen from water," you are correct! Other elements are necessary, too, but most of the solid mass and all of the energy in a plant come from these things.

What happens to energy that is stored in plants? Review the food web diagram below.

Plants capture the sun's energy and store it in chemical bonds. As animals eat the plants, both matter and energy stored in the plant are passed on. Each time matter and energy are passed to another organism, much is lost. If plants or animals are preserved, the matter and energy are preserved as well. Fossil fuels form when large amounts of plant (and sometimes animal) matter is preserved in Earth's rocky layers.


Write a short essay describing the pathways for converting and storing light energy as chemical energy. Share your essay with a parent, teacher, friend or classmate.

Review science lab safety rules here.

Get the plug-ins: Get Adobe Acrobat Reader and Get Quicktime Player. (The QuickTime plug-in is needed to play sounds and movies correctly.)

Want to share photos of you or your friends doing this activity? Send it in an e-mail with the following information:

  1. The title of the activity
  2. The URL (Internet address)
  3. Your name.

Remember that no pictures can be used that show student faces or student names on it. 

Teachers should view the Teacher Site Map to relate Sci-ber text and the USOE Earth Systems Science core.


Updated October 24, 2008 by: Glen Westbroek

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