• During the discussion of the process of photosynthesis, orally check for understanding by asking students: “Why is energy important to living things? Can you name several organisms that can perform photosynthesis? What is the main source of energy on Earth?”

• During the lab, rotate between student teams and assess whether they understand the purpose of the lab by discussing their data and the answers to the analysis questions. Monitor their responses and correct misunderstandings, if necessary.

• Collect and check students’ Levels of Organization graphic organizers.

• Assess student organization of levels through by reviewing the graphic organizers.

• Collect Lesson 1 Exit Tickets for a quick assessment of whether students understand that the Sun is the ultimate source of energy for photosynthesis.

Have students think of the very last thing they had to eat. Ask them, “Why do we get hungry?” Elicit the answer that food provides us with energy to live and grow. Show them an Elodea cutting and ask, “Do plants need energy as well? They need to live and grow.” When students agree, ask them where plants get their energy.

Part 1: Levels of Organization in Plants

Show students an image of plant cells under a microscope such as the Elodea Leaf Cells video available at the Microscope Imaging Station: https://www.exploratorium.edu/imaging_station/gallery.php?Asset=%3Ci%3EElo dea%3C/i%3E%20leaf%20cells%20with%20structures%20labeled&Group=&Cat egory=organelles&Section=

Alternatively, make copies of the Elodea Leaf Cells activity sheet (S-7-8-1_Elodea Leaf Cells.docx), and distribute copies to students.

Explain that chloroplasts are a type of organelle, a small structure in a cell that has a specific function. Ask students to predict which plant cells would have the most chloroplasts, leaf cells, cells from the stem, or root cells, and have them explain their reasoning. Have each student sketch a plant cell, showing chloroplasts. (Note: Alternatively, have groups of students examine Elodea cells under microscopes and sketch them, labeling the chloroplasts.) Ask students if they think human cells have chloroplasts in them.

Define the following levels of organization in terms of an Elodea plant: organelle, cell, tissue, organ, and organism. Distinguish between chloroplast (i.e., an organelle) and chlorophyll (i.e., a pigment found in chloroplasts). Explain that a leaf is considered an organ because it is made up of several types of tissues, such as the veins (the tissue that transports materials into and out of the leaf) and the mesophyll (the tissue where photosynthesis takes place).

Guide students in creating a graphic organizer in their science notebooks that consists of the five levels of organization. Have students write the levels of organization from smallest to largest (organelle, cell, tissue, organ, and organism) and be creative as to how they set it up in their graphic organizers. Examples could include concentric circles, overlapping squares, concept maps, etc.

Example:

For examples of different types of graphic organizers, visit the following Web site: http://freeology.com/graphicorgs/

Have students answer the following question on a Lesson 1 Exit Ticket (S-7-8-1_Lesson 1 Exit Ticket.doc):

“What is the original source of the energy stored in the sugar produced by plant cells?”

Part 2: What is Photosynthesis?

Explain that energy is important because it powers life processes. Living things obtain energy from the food that they eat, or in the case of plants and several other types of living things, they produce their own food. Explain that the Sun is the ultimate source of energy for living things on Earth. Living things that can use the Sun to make their own food can carry out photosynthesis.

Explain that photosynthesis means “made by light.” Tell students that the food that plants make supplies them with energy and it also becomes a source of energy for the living things that eat the plants. Ask students: “What would happen without plants on Earth?” Explain that certain bacteria and algae can also perform photosynthesis.

Tell students that plants have pigments, which are molecules in cells that absorb light energy. The main pigment for photosynthesis is chlorophyll and it gives plants their green color. Chlorophyll captures energy from the Sun and the plant turns it into food in the form of glucose, a type of sugar. Have students work in small groups. Give each group five index cards or strips of paper and have them label the strips: oxygen, sunlight energy, glucose (sugar), water, and carbon dioxide. On the board, write the blank equation for photosynthesis:

_____ + _____      sunlight       _____ + _____

Explain that the arrow means “yields.” Orally describe the process of photosynthesis and have students arrange their index cards in the correct order while you describe the process. Circulate around the groups and make sure that they have arranged the reactants and products of photosynthesis correctly.

carbon dioxide + water      sunlight     glucose + oxygen

Also, ask questions to ensure that students understand that plants store energy from photosynthesis in the form of glucose molecules.

Part 3: Rate of Photosynthesis Lab Investigation

Note: Before beginning this activity, use scissors to make an Elodea cutting for each group, cutting the stems in between the leaf nodes. Elodea is a leafy flowering plant commonly found in aquariums. Its leaves are thin and transparent; most leaves are only two cell layers thick. It can be purchased at pet shops or aquarium stores, or online at sites such as Carolina Biological Supply available athttp://www.carolina.com/product/living+elodea+tips.do?keyword=elodea&sortby=bestMatches. Cabomba is another aquatic plant that will work for this lab and can be readily obtained from tropical fish suppliers. If you cannot obtain aquatic plants for this lab, try the interactive photosynthesis simulation titled Water Weed Simulation available at http://www.saddleworth.oldham.sch.uk/science/simulations/waterweed.htm.

Have students remain in small groups and distribute the following to each group: Elodea cutting, test tube, baking soda, test tube stopper, and the Rate of Photosynthesis Lab worksheet (S-7-8-1_Rate of Photosynthesis Lab.docx and S-7-8-1_Rate of Photosynthesis Lab KEY.docx). (If necessary, a lamp can be used in place of direct sunlight.)

Ask students what factors they think could affect the speed of photosynthesis in plant cells. Elicit that the amount of light is one factor, and guide the whole class in writing a hypothesis about the relationship between the amount of light and the rate of photosynthesis. Have each student record the hypothesis on the lab worksheet.

In groups, have students follow the procedures on the lab worksheet to conduct the investigation and then answer the analysis questions.

Extension:

• Students performing above and beyond the standards can view a simulation of photosynthesis and describe the role of ATP in the photosynthesis process. Have students create a flow chart that traces the steps of photosynthesis, showing the role of ATP through the process. Animations may be found at the following Web sites:

• Photosynthesis Light Reactions http://www.fw.vt.edu/dendro/forestbiology/photosynthesis.swf

• Photosynthesis Animation

http://www.johnkyrk.com/photosynthesis.html.

• For students who may need opportunities for additional learning, verbally accept their responses to the lab questions.

• For students who may not be able to perform the physical aspects of the lab activity, select an aide or a pair of students to assist them during the lab (i.e., have students direct you or class aides to manipulate lab equipment).