Students use perception sketches to illustrate their observations as they listen to the National Geographic video “Ultimate Enemies.”
Tell students that they are going to make perception sketches. Instruct students to close their eyes and listen to what they hear in the classroom savanna food web. Have students listen carefully for one minute. Afterward, tell them to draw symbols and shapes (not words) in their notebooks to describe what they heard. Have students share their observations aloud. Discuss similarities and differences in what they heard. Next, explain to students that they will make another perception sketch, but this time they will be listening to the National Geographic video “Ultimate Enemies.” Encourage students to listen for and sketch multiple layers of what they hear. After listening to the video, write the following questions on the board and have students share their observations aloud. Ask:
- What symbols or shapes did you sketch? What do they represent?
- What is the video about?
- Where did the video take place?
- What types of animals did you hear?
- What type of ecological community or ecosystem do you think is represented in the video?
Elicit from students that the video is about a community of organisms that includes birds, lions, hyenas, and elephants. Explain that this particular community lives in Botswana, Africa.
2. Students use perception sketches to illustrate their observations as they watch the same video.
After listening to the video and discussing their perception sketches, students may not know the ecosystem type yet. Without telling students the ecosystem type, play the video again, but this time allow them to watch and listen as they record their observations and responses to the questions in their notebook. Afterward savanna food web, discuss students’ observations. Discuss the questions again, noting whether or not students’ answers have changed or become more refined. Elicit from students that the video is about organisms living in an African savanna ecosystem. Explain that a savanna is a type of tropical grassland with scattered trees.
3. Build background about ecosystem ecology: environment and communities.
Draw a two-column chart on the board and write the following heads: Terms and Notes. Then write the following terms in the left-hand column: ecosystem, environment, organism/community, food chain, and food web. Provide students with the Two-Column Chart worksheet or have them draw the chart and write the terms in their notebooks. In the right-hand column next to the term ecosystem, have students record the ecosystem type (savanna) shown in the video. Next, have them write a description of the savanna’s environment next to the term environment. Ask: What are the nonliving components that characterize the environment of the ecosystem? Elicit from students that environments are characterized by soil, water, temperature, sunlight, wind, and rainfall. Explain that the African savanna is also called tropical grassland. It has warm temperatures year-round and rainfall is seasonal, being highest in the summer. The savanna is characterized by grasses and small or dispersed trees that do not form a closed canopy, allowing sufficient sunlight to reach the ground. Tell students that a group of organisms interacting in a specific region under similar environmental conditions is called a community. Display the African Savanna Ecosystem illustration. Have students use the illustration and their video observations to record several organisms that make up the African savanna ecosystem savanna food web.
4. Identify African savanna feeding relationships: food chains and food webs.
Ask: What is a food chain? (A food chain is a group of organisms linked in order of the food they eat, from producers to consumers, prey to predators, and scavengers to decomposers.) Using the two-column chart, have students identify one or more food chains using the organisms they listed in Step 3. Elicit responses that include organisms from different feeding levels: producer, primary consumer (herbivore), secondary consumer (carnivore), omnivore, decomposer, insectivores, scavengers, and detritivores. Use the African Savanna Illustration Key to write at least two sample food chains on the board and label their feeding levels. Ask: Why do food chains have arrows between organisms and not just straight lines? Elicit from students that arrows represent the flow of energy and matter between feeding levels. Be sure to point out the role of decomposers, omnivores, and other feeding groups with which students may be less familiar. Ask: What is a food web? How is a food web related to a food chain? Elicit from students that food chains show only one path of food and energy through an ecosystem. In most ecosystems, organisms can get food and energy from more than one source, and may have more than one predator. Healthy, well-balanced ecosystems are made up of multiple, interacting food chains, called food webs. As a class, have students practice combining two of the savanna food chains to create a food web savanna food web.