Lesson 5.3 - Carbon and Oxygen Cycle

You breathe air for two reasons.  One is to get a fresh supply of oxygen to your body cells.  The other is to get rid of the carbon dioxide waste that is produced by your body cells.  Where does the fresh oxygen come from that you and all living things need?  Why is carbon related to the oxygen cycle? 

Read The Carbon and Oxygen Cycles on page 249. Then, answer the following questions.

 

Question 1. How are carbon and oxygen cycled on Earth?

Question 2. One part of the carbon-oxygen cycle is the removal of carbon dioxide from the atmosphere and release of oxygen.  What is the name of the process that does this?

Question 3. Carbon dioxide is released into the atmosphere in many ways.  What are the four ways discussed in the reading?

Question 4. Before humans arrived, the carbon-oxygen cycle was slightly out of balance.  Some carbon was being removed from the cycle.  How was this carbon removed from the cycle and where was it stored?

Question 5. How have humans changed the carbon-oxygen cycle?

Question 6. What is the driving force behind the carbon-oxygen cycle?

 

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. How are carbon and oxygen cycled on Earth?

Carbon and oxygen are cycled on Earth by living organisms.  Plants break down carbon dioxide into carbon and oxygen.  The carbon is stored in glucose and oxygen is released as a waste gas.  Plants and animals use the carbon that is stored in the glucose as an energy source producing carbon dioxide as a waste gas.

Question 2. One part of the carbon-oxygen cycle is the removal of carbon dioxide from the atmosphere and releasing oxygen.  What is the name of the process that does this? 

Photosynthesis is the name of the process where carbon dioxide is removed from the atmosphere and oxygen is released.

Question 3. Carbon dioxide is released into the atmosphere in many ways. What are the four ways discussed in the reading?

The four ways that carbon dioxide is released into the atmosphere are

        1. cellular respiration
        2. natural fires such as forest fires
        3. burning of fossil fuels
        4. decomposers breaking down dead organisms and wastes

Question 4. Before humans arrived, the carbon-oxygen cycle was slightly out of balance.  Some carbon was being removed from the cycle.  How was this carbon removed from the cycle and where was it stored?

Some carbon was removed from the cycle in a slow process that produced fossil fuels.  Some plant material was not completely decomposed and was turned into oil, coal, and natural gas.  This carbon is stored as fossil fuels as shown in figure 12.9.

There is another way that carbon is removed from the cycle that is not mentioned in the reading.  Marine animals use carbon to produce their shells.  The shell material is a carbonate. When the shells are buried and compressed, limestone is produced. 

Question 5. How have humans changed the carbon-oxygen cycle?

Modern humans are exploiting fossil fuels.  When fossil fuels are burned, vast quantities of carbon dioxide are produced.

Question 6. What is the driving force behind the carbon-oxygen cycle?

The sun is the driving force behind the carbon-oxygen cycle.  The sun provides the energy needed for photosynthesis. 

 


Go to the next page to continue Lesson 5.