To help students understand that energy from the sun is necessary for life on earth.
This lesson uses the book Living Sunlight: How Plants Bring the Earth to Life to teach students the basics of photosynthesis and the role the sun plays in keeping plant and animal life alive and thriving on earth. The illustrations are as much a teaching tool as the text.
The book, which is written by Molly Bangs and Penny Chisholm, is one of the winners of the 2010 SB&F Prize for Excellence in Science Books. (You can read about this prize at Book Award.)
Students in grades 3 to 5 know that plants need sunlight to grow, but they may not know how important sunlight is for plants, animals, and humans to survive. The science behind photosynthesis is a little complicated for this age group, but teachers can lay the groundwork for understanding through reading the book and doing the related activities.
In this lesson, students will learn that some animals eat only plants while others eat both plants and animals. They will learn that when humans eat animals that eat plants, the humans absorb the nutrients in the plants. This will help them understand that substances can change form and move from place to place (the plants being eaten by animals), but the substances always come from somewhere (sunlight) and never just disappear (our bodies use the plants for energy).
According to the learning goal for this lesson, most foods animals eat can be traced back to plants. (Benchmarks for Science Literacy, p. 119.) When we humans eat animal products, like beef or chicken, we are absorbing the foods the animals ate, like grasses, grains, and seeds.
All animals depend on plants. Some animals eat plants and others eat animals that eat plants. An organism's patterns of behavior are related to the nature of that organism's environment, including the kinds and numbers of other organisms present, the availability of food and resources, and the physical characteristics of the environment. When the environment changes, some plants and animals survive and reproduce and others die or move to new locations.
If you think it would be useful, you could purchase a DVD of the book at Nutmeg Media. This DVD could be projected onto a screen and you could use it as a supplement to the book to help you point out ideas shown in the pictures.
For some background information on the book, you could listen to the podcast interview with Molly Bang, who is one of the authors and the illustrator of the book.
Before proceeding with this lesson, you will need to spend some time with the book, reading the story plus the notes at the end of the book. The notes at the back of the book explain the concept of photosynthesis in detail and interpret the illustrations, which are central to understanding.
Begin by leading a discussion about the basic concept of photosynthesis so you can measure what students know about the connection between sunlight, energy, and plant life. Lead a class discussion by asking students these questions:
- We all need energy to grow and live, but plants, animals, and humans get their energy from different places. Where do you think plants get their energy?
- (They get their energy from sunlight.)
- Where do humans and animals get their energy?
- (They get their energy from plants.)
- So what does this mean?
- (It means that the energy for all life comes from sunlight.)
- Did you know that animals and humans cannot live without plants?
- (This question will help you gauge students' understandings and misconceptions about the importance of plant life.)
This may be a good time to use the K-2 Printables for Living Sunlight to help assess what students know about photosynthesis. These printables introduce the basic concepts.
Now read the book to the students. Ideally, they will have several copies so they can follow along in small groups as you read. Be sure to hold the book up so they can see the pages. This book has many illustrations that are more than what meets the eye, so you will want to discuss the illustrations as you read. They serve as a visual explanation of the concept of photosynthesis. You will need to read slowly so students will have time to absorb the concepts. Pause for questions, and ask students to describe what they see in the illustrations.
To help facilitate understanding, set a common houseplant within your reach. As you read and discuss the photosynthesis process, hold the plant up in front of the class and point to the different parts of the plant.
Read the first two pages out loud. Pause to ask students:
- Who is telling this story?
(The sun is telling the story.)
Read two more pages. Pause to ask students:
- What are all these yellow dots?
- (They are sunlight.)
- What is in these yellow dots?
- (The energy the sun makes is in the yellow dots.)
Read the next four pages and pause to discuss the photosynthesis process. Talk students through the process using these questions:
- See the first illustration, the magnified image of the roots? What are the roots doing?
- (They are sucking up water from the earth.)
- Point to the second illustration. What's happening in this box?
- (The plant is absorbing energy from the sun.)
- Point to the third illustration. What's happening here?
- (The plant is breaking the water into hydrogen and oxygen.)
- Point to the last illustration. What's happening here?
- (The plant is trapping the energy from the sun.)
Read the next four pages.
- Did you know plants make sugar?
- (Answers will vary.)
- Is this sugar like the regular kind of white sugar?
- (No, that kind of sugar is called sucrose. The kind of sugar plants make is called glucose.)
- How do plants use this glucose?
- (They use it to grow and be healthy. They use it to make seeds and fruits and flowers.)
Read the next two pages.
- Since humans don't have leaves, how do we get energy from the sun?
- (We eat the plants.)
Read the next eight pages.
- Breathe in the air. Where are you getting this air or oxygen?
- (We are getting it from plants.)
- Breathe out. What are you breathing out?
- (We are breathing out carbon dioxide.)
- What happens to that carbon dioxide?
- (The plants breathe it in and use it to make more food.)
Read the next page.
- Look at this illustration. What are you seeing?
- (We are seeing the circle of life.)
- What does the circle of life tell you about photosynthesis?
- (It tells us that all living things need energy from the sun to survive.)
Read the last page.
- How do you know you have living sunlight inside you?
- (We are alive because we eat plants and animals that eat plants.)
After you have read the book to the students, as a group, students should follow the directions on the Living Sunlight student sheet to help them plant a few seeds in a paper cup with soil and place it in the sun. They should plant the same kind of seed in another paper cup but place it in a dark place. After a few days, have the students check on the seedlings. If the cup in the sun has sprouted, ask the students to talk about why one cup sprouted and the other didn't.
Leave the sprouted seedling in the sun, and place a clear jar over it overnight. In the morning, have the students check the seedling. There should be condensation on the inside of the jar. Discuss with students the condensation being evidence of the plants breathing out oxygen, which is called transpiration and is part of the photosynthesis process.
Have students answer the questions on the Photosynthesis and Respiration Printable #6a. You can also use the Steps of Photosynthesis Printable #7 to have students describe, in their own words, the photosynthesis process. The illustrations in this printable are the same as in the book.
As a follow-up activity to this lesson, bring to class these vegetables to represent parts of a plant: broccoli (the flower), celery (the stem), carrot (the root), and tomato (the fruit). Hold up each one and discuss with students how eating these vegetables and fruit gives us energy from the sun to fuel our own energy. The sunlight went into the plant and helped the plant make energy. If we eat the plant, we get the energy. If animals eat the plant, they get the energy. Then, if we eat the animals, we get the energy one step removed. If possible, students could each bring a salad ingredient to class so that they could make a salad and eat it, knowing they are powering their bodies with energy from the sun.
Cycle of Life 1: Food Chain explores the interdependence of food chains and food webs. Students will learn how other organisms in our environment, like insects, depend on plant food too, and how different habitats influence what survives within them.
How a Blue Crab Changes as It Grows examines the blue crab and its habitat and life span to show students that certain factors influence how animals survive and reproduce.
Introducing Biodiversity explores biodiversity and the relationships that exist among organisms and the kinds of environments that support or threaten their existence.