Download Breaking It Down

Science 7 Standard 4 08-06
8/22/02
7:49 AM
Page 155
Standard Indicator
7.4.8
Breaking It Down
Purpose
Students will describe how organisms that eat plants break down the
plant structures to produce the materials and energy that they need
to survive, and in turn, how they are consumed by other organisms.
Materials
For the teacher: cracker
For each student: 3 crackers, copy of Black Line Master (BLM)
Breaking It Down, 2 paper cups, 2 stirrers, water, iodine, medicine
dropper
Activity
B. Activity
1. Distribute a copy of the BLM Breaking It Down and the materials
listed on the BLM to each student.
(continued)
Standard 4 / Activity 5
Indiana Science Grade 7 Curriculum Framework, October 2002
NEEDS
For students who are
having difficulties
understanding the
concept, compare
cellular respiration to
depositing money into
a vending machine.
Explain that you have
a dollar bill but the
vending machine does
not have a bill
receptacle. Explain that
you must convert the
dollar down into
another form (coins)
in order for the vending
machine to work. Ask
students to think
of other analogies.
connecting
across the
curriculum
Visual Arts
Have students use
pictures from old
magazines and their
own drawings to create
a mural that depicts
the process by which
animals obtain useable
energy from plants.
Standards Links
7.4.6, 7.4.7
page 155
Standard 4
A. Pre-Activity Discussion
1. Ask students: “How do we get energy?”
2. Discuss how animals eat plants and other animals to get energy.
Explain that plants store light energy in sugars, and that animals
eat the plants to obtain this stored energy.
3. Ask students: “How do we get energy from eating plants?”
4. Explain that we begin with digestion of plant material.
5. Hold up a cracker and ask: “What is this cracker made from?”
6. Explain that crackers are made from plant materials, and since
plant materials contain stored sugars, the cracker contains
stored sugars.
7. Give each student a cracker to chew and ask: “When does
digestion begin?”
8. Explain that digestion begins as soon as they begin to chew.
Explain that as they chew on the cracker, their teeth physically
break down the food, and that enzymes in their saliva chemically
break down the food into smaller substances.
9. Explain that foods we eat are made of substances too complex
and large for our bodies to directly obtain energy from them.
Explain that the mixing of saliva with foods begins the process
of breaking down this stored energy.
meeting
individual
Science 7 Standard 4 08-06
8/22/02
7:49 AM
Page 156
Activity (continued)
2. Instruct students to read the procedure and ask: “What do you
predict will happen when iodine mixes with the cracker and
water? What do you predict will happen when iodine is mixed
with the cracker you have already chewed?”
3. Direct students to follow the procedure on the BLM. Monitor
students as they work.
4. Ask students if their predictions were correct. Discuss how the
iodine reacted with the cracker and water, testing positive for the
presence of starch, while the cracker and saliva tested negative.
5. Ask students to give an explanation of the results.
6. Discuss with students how the cracker and saliva tested negative
for the presence of starch because the enzymes in the saliva had
already broken down the starch into other substances.
Standard 4
C. Discussion
1. Tell students that every cell in the body needs energy to do work
(e.g., cell division, getting rid of wastes, etc.).
2. Explain that digestion breaks down foods into smaller substances,
but that these substances are not the right form to be used,
so they go through another process called cellular respiration.
3. Tell students that cellular respiration is the process by which
stored chemical energy in substances is broken down and
converted into energy that can be used by the cell. Explain that
cellular respiration takes place in the cell, specifically in the
mitochondria of eukaryotic cells.
4. Ask students to explain what happens when one animal eats
another animal or a plant.
5. Discuss how chemical energy is stored in animal cells and that
digestion and cellular respiration release the energy for cell work.
6. Review how light energy is captured and stored in plants,
released through digestion followed by cellular respiration,
and then travels through the food chain as organisms eat
other organisms.
Classroom Assessment
Basic Concepts and Processes
Throughout the activity, ask questions, such as the following:
How do organisms break down plant structures to produce
the materials and energy they need to survive?
How does energy from the sun travel through the food chain?
How do you know that enzymes break down starch found
in foods?
page 156
Standard 4 / Activity 5
Indiana Science Grade 7 Curriculum Framework, October 2002
Science 7 Standard 4 08-06
8/22/02
7:49 AM
Page 157
Name:
Breaking It Down
Iodine reacts with starch (a sugar), showing a bluish-black color.
What happens when iodine is added to saliva mixed with sugars found in foods?
Materials:
two crackers
two paper cups
water
two stirrers
iodine
medicine dropper
Procedure:
1. Break one cracker into pieces into a cup and add several drops of water.
2. Mash the cracker into the water with a stirrer.
3. Chew the second cracker until it is mushy, but do not swallow it.
4. Spit the chewed cracker into the second cup.
5. Place 5 drops of iodine into each cup and stir.
[Be sure to use two separate stirrers.]
6. Compare the results.
7. Dispose of the cups properly.
Standard 4 / Activity 5
Indiana Science Grade 7 Curriculum Framework, October 2002
Black Line Master 1
page 157