Food Webs and the 10% Rule: Following the Energy

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Science · Environmental Science / Earth Science
SP-ENVS-001  ·  Free to print and use in your classroom  ·  substituteplans.com
Page 2
Food Webs and the 10% Rule: Following the
Energy
Science · Environmental Science / Earth Science · Grades 9-10 · 50 minutes
Time needed
50 minutes (one class period)
Prep
Copy the 2-page worksheet (one per student). Write the 10% rule on the board.
Technology
None. Calculators are optional.
Student
independence
High. Students read and work alone, then compare with a partner.
Copies to make
One 2-page worksheet per student
Materials
Pencils, Worksheet, Calculators (optional)
Goal for today: Students will identify producers, consumers and decomposers and will use the 10% rule to calculate
the energy available at each trophic level.
Before the bell
☐ Copy the worksheet, one per student (2 pages).
☐ Write on the board: 10% RULE: Only about 10% of the energy at one level reaches the next level. To
find it, multiply by 0.1 (or divide by 10).
☐ Keep the answer key on your desk. You do not need any science background to run this lesson.
Say this to start
Good morning! Today’s science lesson is about how energy moves through nature, from plants to the animals that eat
them. You will read a short passage, fill in some vocabulary, and then do a few simple calculations. Each calculation
uses one rule, and it is written on the board. Work on your own first, and we will check answers together near the end.
Run of show
Minutes
What you do
What students do
0–5
Take attendance the way the school requires. Hand out the
worksheet and read the title and directions aloud.
Settle in and look over the worksheet.
5–13
Tell students to read the passage silently. Point out the
10% rule on the board.
Read silently. Underline the words
producer, consumer and decomposer.
13–23
Tell students to use the word bank to finish questions 1–4,
then fill in the energy pyramid table.
Complete the fill-in-the-blank items and the
table.
23–35
Tell students to complete the calculations (questions 5–7).
Walk around. If a student is stuck, ask, “What is 10% of
that number?”
Calculate each level in the work box. Show
the math.
35–44
Tell students to answer questions 8–12. Partners may
compare answers quietly.
Answer the multiple-choice and
short-answer questions.
44–50
Read the answers to questions 1–10 aloud from the key.
Collect all worksheets.
Check their work, then hand in the
worksheet.


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Science · Environmental Science / Earth Science
SP-ENVS-001  ·  Free to print and use in your classroom  ·  substituteplans.com
Page 3
If things go wrong
• If students say they have not learned the 10% rule, tell them the rule is on the board and the passage
explains it. The whole lesson is practice.
• If a student has trouble multiplying large numbers, allow a calculator or show that 10% means moving the
decimal one place left (or dropping one zero).
• If students finish early, check that every calculation has the math written, then use the early finisher list.
• If the class gets noisy, remind them this is independent work until the last 10 minutes.
Early finishers
• Draw a food web with at least six organisms from a pond, forest or desert. Draw arrows from the food to the
eater.
• Write a sentence explaining why there are fewer hawks than grasshoppers in a grassland.
Support and challenge
• Support: Let students use a calculator and complete only questions 1–7 and 11.
• Challenge: Ask students to work out how much energy would reach a fifth level if the producers held 50,000
kcal, and to explain why a fifth level is rare.
Notes for the teacher (you fill this in)
Jot a few lines before you leave. A full Daily Sub Report is in the free Sub Survival Kit at SubstitutePlans.com.
How far the class got / what to pick up next:
Students who were especially helpful:
Anything the teacher should know: