Science/Strand III/Content Standard 2/Middle School/Benchmark 3
Benchmark Question: How do living things obtain and use
Focus Question: What evidence is there that plants
make and store food?
- Observe chloroplasts in
special plant cells by looking at plant leaves under a microscope. (If
needed, prepared slides may be used to help students in locating the
- Draw a diagram of what they
observe under the microscope.
- Discuss their data and
observations with others to determine the location of specialized
plant cells where photosynthesis occurs.
The teacher will explain the
- During photosynthesis,
certain raw materials (carbon dioxide + water) are taken in and
chemically combined in the chloroplast to form new products (sugar and
- The plant then uses the
sugar immediately as food or stores it as starch in a special food
In order to develop an
understanding of how plants store food, students will examine various food
storage organs (e.g., potatoes, onions, carrots). They will conduct a
simple iodine/starch test to discover that the storage organ is a vessel
that plants use to store food energy.
A simple iodine starch test
involves dropping iodine solution on a piece of food. Initially, iodine
appears reddish-brown in color. When iodine comes in contact with starch,
it turns to a bluish-black indicating the presence of starch.
Then, students will
participate in a guided discussion of the food storage organs:
1. What happens to a food storage organ in your
cupboard? (Gets smaller, starts to grow sprouts, develops brown spots.)
2. Why is this happening? (It is losing water, growing
roots, decomposing [chemical change.])
3. Where is it getting the energy to grow sprouts? (From
the food energy stored within the cells of the storage organ.)
Students will design an
investigation to test their hypothesis about what is happening to their
potato, onion, or carrot.
Follow up with a discussion
and presentation of data from the investigations.
End the lesson with a “Did
You Know…” i.e., Native Americans in South and Central America first
cultivated many tuber plants, like the potato. One of these plants has
erroneously been called the Irish potato. Its fried version is called
French fries. Ask the students to talk about what observations they can
make from this interesting story.