Chapter 7 Lesson 3 "How Plants Give Off Oxygen"

Materials:

• 2 bottles, 2 balloons that fit over the bottles and a heat source.
• Worksheet, "How Plants Give Off Oxygen"
• Worksheet "Life of an Oxygen Atom"

Objective:

• Students will identify the importance of oxygen for living things,
• Students will describe how plants produce an release oxygen.

Alaska Content Standards:

• SCI A-10 Students will understand that living things are made up mostly of cells and that all life processes occur in Cells (Cells)
• SCI A-12 Students will distinguish the patterns of similarity and differences in the living world in order to understand the diversity of life and understand the theories that describe the importance of diversity for species and ecosystems.
• SCI A-14 Students will understand the interdependence between living things and their environments; that living environments consists of individuals, populations, and communities; and that a small change in a portion of an environment may affect the entire environment (Interdependence);
• SCI A-15 Students will use science to understand and describe the local environment.

Anticipatory Set: You can do this in your classroom with me if you like. I will take the two bottles and place a balloon over the top of each bottle. Take a heat source and begin heating one of the bottles. The balloon will begin to rise. Have the students try to explain what is happening. Ask the question, air is a gas, does this happen with a solid? Why is there such a difference between the way this happens in a solid and how it happens in a gas. Then explain the process using these points.

• In solids the molecules are strongly bonded to one another, thus forming a rigid solid.
• When heating a solid molecules move(vibrate) faster which causes a small expansion but the bond between different molecules does not break.
• In a gas the type of bonds between molecules is much weaker and molecules move much freely about allowing them to expand the area they occupy much quicker and easier than with a solid.
• Because the air around us is a gas the bonds can be broken easily with our hand. We can wave our arms, and break bonds in the air easily. If we were in water the bonds between molecules are a little stronger but they can still be broken. You can get in the water and wave you arms. Is that easier or harder? Why? (Let students answer) If you were frozen into a solid block of ice. Could you still wave your arms? Is it possible to break the bonds in a solid?
• The important thing to realize is that even though you can't really feel the air around you as you sit there is is there. You are on the bottom of a big Ocean of air that surrounds the Earth. What do we call it? If you fan yourself or go out into a wind storm you can feel it.

Teacher Input:Today we are talking about How Plants Give Off Oxygen. Why would we start out talking about gases? (Allow students to answer) Well, how much of the Earth's atmosphere is made up of Oxygen? Show this diagram and ask: If we need Oxygen and Plants need carbon dioxide which organism has a harder time getting what they need? How much of the atmosphere is oxygen, how much is Carbon Dioxide? We know plants need carbon dioxide and water but do they need any of the oxygen to, do they need any of the carbohydrates they produce?

Show this picture of an energy cycle within a plant cell. All living cells use some chemical substance for energy to power the work that a cell does. Within plants and animals the sugar that is created is used to power the work that a cell does. These cells have an organelle called a mitochondria that helps break down the sugar and get ATP (power storing chemical) out of it. Define Cellular respiration: (P152)

Show this picture, it might help to think of cellular respiration like this: the cell is a car that needs to go somewhere. To get the car to go you need to burn gasoline with oxygen, your cells need carbohydrates and oxygen. For your car to get power out of the gasoline your car needs an engine, your cells need mitochondrion. The situation is closer than you might think. Gasoline is formed by a carbon chain, like carbohydrates and if you could burn gasoline cleanly you would get CO2 and H2O with no impurities. Your body is able to "burn" carbohydrates cleanly and the result is CO2 and H2O. Your body then gets rid of these waste products.

Show this picture: The process of cellular respiration has three steps: glycolysis, Krebs cycle, and the electron transport chain. Go through the diagram. Here is a great song to go along with this:

http://biology.clc.uc.edu/courses/bio104/atp.htm

http://biology.clc.uc.edu/Sounds/Bio104/atp-stereo.rpm

Show this picture: Basically the process goes like this: Sugar molecules are broken down into Pyruvic Acid and then as energy is released from the Pyruvic Acid 3 molecules of Carbon Dioxide are created. Three molecules of Water is created and 34 molecules of ATP(chemical energy) are created.

For more detailed explanation try http://biology.clc.uc.edu/courses/bio104/cellresp.htm

Teacher Modeling: Show this diagram from P153. and/or this diagram So there is this continual cycling of Oxygen, Carbon dioxide, and water. While looking at the diagram have the students list three sources of carbon dioxide. Starting with oxygen entering a living organism have the students track an Oxygen atom though the cycle.

Check for Understanding: Students most likely completed a very short cycle and left a lot of things out. Remind them of this structure, pic 1, pic 2, pic 3, Pic 4 that we talked about the other day. Have the student look at their worksheet, "Life of an Oygen Atom" and starting with the lung have the students put the order of the oxygen atom through the Oxygen, carbon dioxide cycle on the paper.

Guided Practice: Students will have difficulty with this walk them through it.

Closure: Students have know learned some of the most difficult parts of biology let them know that and take questions.

Independent Practice: Students should complete "How Plants Give Off Oxygen" and then they should take the Chapter 7 Lesson 3.

Duration:

30 minutes + 10-15 for Independent Practice (Could be longer if taken for homework).