Unit A: Organization of Living Things
1. Get Set to Explore
- echolocation: Detecting objects by beaming sound waves at them and sensing the echo; also called sonar.
- navigate: To steer around or through something.
- nocturnal: Relating to an animal that is most active at night.
- sound waves: The passage of energy through a material, causing particles of the material to move back and forth; bats send out high-pitched sound waves through the nose or mouth.
- Make a KWL chart on the board and ask students what they already know about bats; list their ideas in the Know (K) column of the chart. Then ask students what they want to learn about bats; you may wish to let individuals write their ideas in the What (W) column of the chart. You can go over definitions of any of the vocabulary words that students use or ask about during the discussion. Leave the chart up on the board, so that the class can fill in the Learn (L) column at the end of the simulation.
- Take a few minutes to review definitions of the vocabulary words that did not come up in the previous discussion.
- You may wish to ask students to look over information Student Edition page A92, about how bats use sonar, or echolocation, to hunt at night. Explain that they also use echolocation to avoid flying into obstacles. If time permits, let them add to the KWL chart. Present the Discover! question. Encourage students to refer to the KWL chart to formulate possible answers.
2. Guide the Exploration
- Have students launch the Discover! Simulation. Explain that the first part of the simulation shows how bats use echolocation to hunt and navigate around obstacles; after the demonstration, students will use echolocation to help the bat feed and steer.
- Focus students' attention on the sound waves in the demonstration. Explain that the sound waves the bat sends out are in one color; the echoing sound waves are in another. Students should notice how the sound waves that bounce off the tree are different from those that bounce off insects.
- When the demonstration is finished, the controls (an up arrow and a down arrow) will appear at the bottom of the screen. A timer, to the right, indicates how long students have to play the game.
- Ask a volunteer to read aloud the first five sentences of Step 3's Wrap-Up text. Make sure students understand how and when bats are active and that they use echolocation, also called sonar, to navigate. Then have a volunteer read the rest of the Wrap-Up text. Lead a discussion to fill in the L column of the KWL chart.
- Propose that students return to the simulation to do the Extension. Let the volunteers summarize the difference in how the bat's sound waves echo off a tree compared with how they echo off an insect. Guide the class to realize that the size of each object influences how the sound waves bounce off it; help them understand that the movement of the insect influences when the echoing sound waves reach the bat. These differences help the bat differentiate between a tree, which it wants to avoid hitting, and an insect, which it wants to catch.
If time permits, present children with the following questions:
- Critical Thinking Analyze On Student Edition page A92, the Science textbook mentions a kind of moth that can make sound waves similar in pitch to those bats send out. How would sending out such sound waves help the moth? Answer: The extra sound waves would interfere with the echo of the sound waves that the bat sends out. This interference would confuse the bat and make it harder for the bat to locate the moth.
- Inquiry Skill Ask Questions What questions do you have about bats or echolocation? Come up with three or more questions. Answer: Topics students might consider include how young bats become able to use echolocation–through instinct or learning; what other animals use echolocation and for what purpose; how bats that do not use echolocation differ from those that do; how people use the technology of echolocation. Encourage students to use library or Internet resources to answer one or more of their questions.
4. Reaching All Learners
Have interested students learn about the Doppler effect and how it is helpful to bats. They should find common examples of the Doppler effect that people can easily hear. Encourage students to make a poster to illustrate and share what they learned.