Science/Strand III/Content Standard 2/Middle School/Benchmark 3
Instructional Example

Benchmark Question: How do living things obtain and use energy?

Focus Question: What evidence is there that plants make and store food?

Students will:

  • 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 chloroplasts.)
  • 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 following:

  • During photosynthesis, certain raw materials (carbon dioxide + water) are taken in and chemically combined in the chloroplast to form new products (sugar and oxygen).
  • The plant then uses the sugar immediately as food or stores it as starch in a special food storage organ.

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.

Constructing: (SCI.I.1.MS.1), (SCI.I.1.MS.2), (SCI.I.1.MS.3), (SCI.I.1.MS.6).

Reflecting: (SCI.II.1.MS.1), (SCI.II.1.MS.5).