Lesson: Feeding on the Dead

Tell students that they will be using rates to calculate information about decomposing organisms. Ask:

• When do you encounter rates in your everyday life?

• Are these rates helpful? Why or why not?

Have students view the freeze-frame shot before playing the video. Ask: What do you notice? What inferences can you make about the scene? Then play the video, asking students to focus on what the scientists observe and infer about the same scene. Then hold a class discussion about what they learned from the scientists.

Distribute or digitally share the “Word Search” literacy skills sheet. Read the directions aloud. Then have a volunteer read the first section of the article aloud. Ask students to identify words in the first section that they don’t know or are unsure of (some examples may be: delicacy, plankton, carcass, decomposer). Choose one of these identified words to use as a model for filling out the skills sheet. Then have students independently read the rest of the article and complete their skills sheet. Select a few volunteers to share their words and definitions with the class.

After reading the article, ask the following comprehension questions:

• What animals feed on a whale fall? When do they visit the whale carcass? (First, bacteria start to consume the dead whale. This gives off a smell that attracts other organisms. Then scavengers, such as sharks and other fish, feed off the whale meat. Last, zombie worms come to eat the whale bones.)

• Where do the bacteria that first visit the whale fall come from? (They are there all along—the bacteria cover the outside and inside of the whale while it’s alive.)

• What happens to organisms after they decompose? (They are turned back into the elements and chemicals that they are made of.)

• What factors can affect how quickly something decomposes? (temperature, moisture level, pressure, and oxygen level)

Read through the introduction and the example of the “Working With Rate” box on page 19. Focus on Step 2. Tell students that some questions will require multiplication, and some will require division. Show students that they can consider the units of measure to help them decide whether to multiply or divide. They can think about the unit of measure the answer should have and consider how to write the expression to make units cancel out. A question students can ask themselves after solving is, “Should my answer be greater than or less than my starting number?” and consider whether they need to multiply or divide to achieve that. Have volunteers read the questions aloud to the class. After each question, pause and ask students whether they should multiply or divide for this question. Then have students work individually on each problem.

Have students use a map to find driving distances from their homes to 5 different places in the U.S. they’d like to visit that they’ve never been to. Tell them to calculate how long it would take them to get to those destinations if they were traveling at speeds of 30 miles per hour, 45 miles per hour, and 70 miles per hour.