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3.2: Using Food Chains: How Energy Gets to You – Student Edition (Human Biology)

Difficulty Level: At Grade Created by: CK-12
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Begin by discussing the main question posed at the beginning of the section, “Where do you get the energy to live?” Students may not yet have considered that eating food is how animals get energy from the sun. Emphasize that energy is stored in food, so our bodies must be able to release this energy to function.

Carefully analyze the figures with the students to trace the flow of energy backward from the movement of muscles in a finger to the sun by tracing where their breakfast came from.

The reversible nature of the reactions is the key to learning how energy is transferred from the sun to storage molecules in plants (photosynthesis) and then released from these molecules in plants and animals (respiration). Emphasize that green plants perform both photosynthesis and respiration. Green plants have to store the energy from the sun and then release it as they need it.

Activity 2-1: Draw a Food Chain will illustrate that the source of energy is almost always the sun no matter what organism you study in a food chain.

Think about the last time you were exercising so hard that you were panting and gasping for breath. Describe what it felt like in your mouth, your throat, your chest and lungs. Now describe what you imagine is happening to the oxygen and carbon dioxide as it moves in and out of your body.

A suggested response will be provided upon request. Please send an email to teachers-requests@ck12.org.

If oxygen and sugar are the only things required to provide energy to move our muscles, why do we bother to eat other foods? Why do you think we eat other foods, such as potatoes, pasta, meat, ice cream, pizza, and spinach?

What Do You Think?

You might say that you have the energy to wiggle your finger because the sun shines. Read the quote from Steve Van Matre again.

“Each living thing is a spark of sunlight energy, a crystal bead in the net of life.”

-Steve Van Matre

The Earth Speaks

What do you think the author meant when he wrote that sentence?

Photosynthesis/Respiration Play

Students learn about the process of photosynthesis and respiration by creating and performing a skit. Encourage the students to be creative. The following is a sample play written by a group of students at Egan Middle School.

Cast of Characters: Narrator 1, Narrator 2, Sun, Water, Carbon Dioxide, Oxygen, and Sugar

Setting: A cell is represented by a sheet spread over four stools. Arrange the sheet so that the front is totally covered and there is a space for people to hide in the back. All characters except oxygen, sugar, and the sun are standing in the “wings.” Oxygen and sugar are hiding behind the sheet. The sun is crouching a few feet away from the cell.

Narrator 1: (Reads the cast of characters) The sun rose on a new day. (The sun stands and opens its arms) The young plant cell was preparing for photosynthesis. Deep inside the cell's chloroplasts, chlorophyll was absorbing energy from the sun. (The sun pours rays over the cell.) The plant was also absorbing water from the soil. (Water jumps behind cell.) Carbon dioxide entered the plant through tiny openings in its leaves called stomates. (Carbon dioxide floats behind cell).

Narrator 2: During the day, the cell was hard at work performing photosynthesis. (Water and carbon dioxide run around behind the cell.) Finally, the cell was finished and the products of this process were sugar and oxygen. (Sugar and oxygen stand up. Water and carbon dioxide sit down.) The sugar was stored for later use. (Sugar sits.) The oxygen was released into the air for other plants and animals to use in respiration.

The End

A suggested response will be provided upon request. Please send an email to teachers-requests@ck12.org.

  • During what parts of the day does respiration occur in a plant cell? Explain your reasoning.
  • Can plants photosynthesize in the dark? Explain your answer.
  • Give an example of energy used by a living organism that cannot be traced back to the sun.

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Date Created:
Feb 23, 2012
Last Modified:
Apr 29, 2014
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