# Lesson 7: Oxygen Production and Life

## Activities

### Activity 1: Necessary and Interdependent

Materials: scissors*
In this activity, you will explore the importance of photosynthesis and cellular respiration and the relationships between them. Ask your parent which option to complete.
There are two options for this activity. The first is ideally better for the logical/mathematical/analytical thinker, and the second is preferable for the visual or creative learner and is intended to help in answering the questions. Both options essentially require the same level of analytical thinking and the same level of comprehension with the primary difference being the way in which the thought processes are engaged to appeal to various learning styles.

#### Option 1

Consider the following equations. To help reinforce the contents of each equation, write them on the "Equations" page. Next, answer the questions at the top of the "Questions to Consider and Scenario Response" page and then read the scenario at the bottom of the page and answer that question. Part of this activity will require you to make connections based on the information in the equations, so use the "Equations" page if you need to refer to either equation. Feel free to refer back to the readings to answer the questions for this lesson.

As you consider the questions, it is important for you to recognize that the questions are designed for you to take the basic knowledge you have about respiration and photosynthesis and analyze it to find answers to the questions. It may seem difficult, yet press on. The goal of the questions is to make you think critically, so the answers may not be obvious based only on the reading.
 Photosynthesis Carbon Dioxide + Water + Sunlight —> Glucose + Oxygen
 Cellular Respiration Glucose + Oxygen —> Water + Carbon Dioxide + Energy
• How are the two processes interdependent? Oxygen is a by-product of photosynthesis and is required for cellular respiration to occur. By-products of respiration are carbon dioxide and water, which are necessary for photosynthesis.
• Given the fact that both plants and animals require energy for survival, yet it is only plants that produce their own food, how does the environment have enough energy for all organisms? Plants in general are the most abundant organism on the planet. By sheer mass, enough energy is produced and stored by plants to ensure that the ecosystem survives. Plants are not mobile and while they do require energy for survival, there is a point in their life cycles that does not require large amounts of energy for growth or survival. Basically, plants produce an excess of energy. Also, it is of equal importance to recognize that organisms such as animals require a lot more energy for survival and for movement where plants do not.
• Respiration requires oxygen and photosynthesis produces oxygen. Both plants and animals carry out cellular respiration, yet only plants photosynthesize. Why do you think there is enough oxygen to meet the needs of all living organisms? The answer is similar to the previous question. The abundance of photosynthesizing organisms ensures that enough oxygen is produced to sustain an environment under normal conditions. Earth has reservoirs of oxygen as well, ensuring that an abundance of oxygen is present.
• How might an abundance of carbon dioxide be beneficial for the environment? Higher amounts of carbon dioxide could promote plant growth and the production of excess energy and oxygen. While more than just carbon dioxide is required (consider the need for nitrogen and oxygen), if plant growth increases, oxygen does as well. (NOTE: The element that would limit the development of greater amounts of plant growth would be nitrogen.)
Review and discuss your child's answer to the scenario at the end of the activity. Answers will vary, but below is a sample answer.

Individuals in the city and the overall country would have the following concerns. One would be that the failure to produce oxygen means that the oxygen in the water would eventually be depleted. (It would not disappear because oxygen is present in the atmosphere and would eventually diffuse into the water.) The second concern would be that a major food source would dwindle. Without oxygen being replenished by plants in the water, the fish and the plants themselves would be unable to carry out cellular respiration.

#### Option 2

In this option, you will organize drawings and use them to answer questions regarding the importance of photosynthesis and its products for life. First, read the scenario on the "Photosynthesis Description" page. Next, cut out the drawings from the "Photosynthesis Drawings" sheet, and then feel free to manipulate them to help you answer questions effectively. (The questions are located at the bottom of the "Photosynthesis Description" page.)
In this option, your child will manipulate drawings and use them to answer questions regarding the importance of photosynthesis and its products for life. The diagram should show a combination of carbon dioxide, water, and sunlight producing carbohydrates and oxygen. When the carbohydrate is broken down, the diagram should include a carbohydrate and oxygen producing water, carbon dioxide, and energy.

• How are photosynthesis and respiration interdependent?
Both photosynthesis and respiration (the breakdown of the carbohydrate) have as a central element glucose. Glucose, a carbohydrate, is produced when carbon dioxide and water are combined by using energy. As a result of the process, oxygen is also released. Glucose, when broken down, produces carbon dioxide and water. In essence, photosynthesis utilizes the products of respiration, and respiration cannot occur without the primary product of photosynthesis, glucose.
• Given the fact that both plants and animals require energy for survival, yet it is only plants that produce their own food, how does the environment produce enough stored energy for all organisms?
In a healthy ecosystem, one that sees organisms surviving and reproducing, there will always be an adequate number of producers. These producers are the foundation of the food chain and without them, other organisms that have to capture or eat food for energy cannot survive. The abundance of producers ensures that the ecosystem has appropriate amounts of energy. The producers are abundant; when producers decrease, the number of organisms will also do the same.
• Respiration requires oxygen and photosynthesis produces oxygen. Both plants and animals carry out cellular respiration, yet only plants photosynthesize. Why do you think there is enough oxygen to meet the needs of all living organisms?
There is a lot of oxygen in the atmosphere plus oxygen that is in the hydrosphere and stored in carbohydrates. Also, the Earth is a giant ecosystem that sustains itself.
• Challenging Question: How might an abundance of carbon dioxide be beneficial for the environment?
Plants utilize carbon dioxide to produce carbohydrates that are beneficial for energy and for growth. With an abundance of carbon dioxide, plant growth is encouraged. Also, increased plant life insures an oxygen-rich environment.