To explore the process of photosynthesis in the ocean.
This lesson uses the book Ocean Sunlight: How Tiny Plants Feed the Seas to teach students about photosynthesis and its importance of providing food for ocean marine life as well as the oxygen needed to sustain life on earth and in the ocean. The book is written by Molly Bang and Penny Chisholm and is a winner of the 2013 SB&F Prize for Excellence in Science Books.
Students in grades 3 through 5 may not fully understand the connectedness between all living things and may view animals that live on land as mutually exclusive from creatures that live in the sea. They may also not fully understand how connected land and sea animals are to the environment and how these ecosystems are interconnected and crucial to the survival of all species.
In this lesson, students will learn how photosynthesis is crucial for ocean life and how creatures that live deep in the sea depend on sunlight to live, even though they live in dark waters and never benefit from the sun directly. Students will learn what phytoplankton is and how it benefits all animals on land and water.
Ideas in this lesson are also related to concepts found in these Common Core State Standards:
- CCSS.ELA-Literacy.RI.5.1 Quote accurately from a text when explaining what the text says explicitly and when drawing inferences from the text.
- CCSS.ELA-Literacy.RI.5.2 Determine two or more main ideas of a text and explain how they are supported by key details; summarize the text.
Authors Molly Bang and Penny Chisolm also co-wrote the book Living Sunlight: How Plants Bring the Earth to Life, which was a 2010 SB&F Award-winning book and also has a Science NetLinks lesson. It might be useful for you to read this book first, which explains what photosynthesis is and how important sunlight is to plants, animals, and humans on land. You may want to consider offering to students the Living Sunlight science lesson first, followed by this science lesson.
Before beginning this lesson, you should read the book and the notes at the end of the book. These notes explain the process of photosynthesis and how it provides food in the food chain, particularly for marine life. The notes also explain the illustrations and how they will help students “see” the concepts of the book.
Another resource you can look at for background on the book and photosynthesis is the Ocean Sunlight Presentation given by Penny Chisolm during the Family Science Days at the 2013 American Association for the Advancement of Science Annual Meeting. You can either use this presentation for your own information or you can choose to share it with your students.
Begin this lesson by having the students watch in class this short Photosynthesis video. The TV hosts use preparing a salmon salad with different vegetables to explain how photosynthesis works. Because the salad has both plants and fish, the program hosts connect photosynthesis on land to photosynthesis on sea and show how this scientific process results in healthy eating for humans.
Follow this video with a class discussion about what students learned. Ask students:
- How does photosynthesis work on land?
- How does photosynthesis work in the ocean?
- (Plants collect the sun’s energy in their leaves, drink water up through their roots, and pull carbon dioxide from the air. Plants turn these molecules into sugar and then breathe the results of this chemical process into the air in the form of oxygen for all of us to breathe.)
- (Phytoplankton, such as algae, are the plants that make photosynthesis happen in the ocean. These tiny plants live on the surface of the water where they collect their energy from the sun and use it along with nutrients in the water to grow and feed ocean life.)
To begin this lesson, read the book through once to the students. Have the students break out into small groups of four to five students. Each group should have a copy of the book so they can follow along as you read. Hold the book up to the class as you read.
Then read through the book again. This time, as you read, pause to ask the Ocean Sunlight Discussion Questions listed on the teacher sheet and point to the illustrations in the book. The illustrations create a visual explanation of photosynthesis and will further student understanding of the concepts covered in this lesson.
When you have finished reading the book with students, lead a discussion about the food chain by asking students what they ate for breakfast or lunch. Write their responses on the chalkboard or whiteboard. Talk about where each food originated from. Some foods will be obvious, like orange juice, but other foods like pasta may not be so obvious to students. Maybe some students ate a chocolate caramel candy bar for dessert. Where did the caramel come from, or the chocolate? Help students understand that almost everything they eat can be traced back to plants but that the route is sometimes not so obvious.
To assess understanding, ask students to create an ocean photosynthesis poster. Have students break out into groups of two or three. Give each group one piece of poster board and crayons and ask them to draw pictures of big and little fish, phytoplankton, and sea plants—with one eating the other or arrows pointing from one living thing to the next, showing what is eating what. Also ask each group to include one plant or animal that does not belong in the ocean photosynthesis system, and to draw it so that it's not real easy to pick out. Tell students they should also be prepared to explain why that item does not belong in the ocean food chain. After the students have finished their posters, have each group stand up in front of the class and describe what's going on in their poster. Next they should ask their classmates if they can spot the plant or animal that doesn't belong. Once identified, the students should explain why it doesn't belong in the ocean food chain and what food chain it does belong in.
Cycle of Life 1: Food Chain helps students understand that almost every food they eat can be traced back to plants and that the sun is needed for all organisms to live and grow.
Cycle of Life 2: Food Webs focuses on the food chains, food webs, and the interdependence of life.
Living Sunlight: How Plants Bring the Earth to Life is about the basics of photosynthesis in plants. The book this lesson is based upon was written by the authors of Ocean Sunlight.