Oxygen and Carbon Cycle




Like most living things, you need oxygen to survive.
The atmosphere, which is 20 percent oxygen, supplies you and other air-breathing organisms with this vital gas.
Oxygen from the atmosphere that has dissolved in water is breathed by fish and other aquatic organisms.
Clearly, living things would have used up the available oxygen supply in the atmosphere millions of years ago if something did not return the oxygen to the air.
But what could that something be?

Consider this:
When you inhale, you take in oxygen.
When you exhale, you release the waste gas carbon dioxide.
If something used carbon dioxide and released oxygen, it would balance your use of oxygen.
That something is producers such as green plants and certain microorganisms.
These producers use carbon dioxide gas, water, and the energy of sunlight to make carbon containing compounds that are often referred to as "food."
During the food making process, the producers also produce oxygen, which is released into the environment.
Through this process, known as the oxygen cycle, there is always a plentiful supply of oxygen available for air-breathing organisms.

But what happens to the carbon in food?
How is it transformed back into carbon dioxide?
In order to extract energy from food, organisms must digest the food, or break it down into simpler substances.
This process ultimately produces water and carbon dioxide, which are released back into the environment.

Look at the illustrations below that demonstrates the oxygen and carbon cycles.
Look at the illustration below and explain what is happening in the Oxygen and Carbon Dioxide Cycles.


The following picture of the Carbon Dioxide - Oxygen Cycle is missing one phrase or part. Write a phrase or sentence that fills in the missing part. The missing part would have gone in the rectangular box.


In order to have an unending supply of certain chemicals in the world, such as nitrogen and carbon, these chemicals must be


About what percentage of the Earth's atmosphere is made up of oxygen?


Identify the two biological processes that are involved with the oxygen/carbon dioxide cycle.


Why is the amount of carbon dioxide introduced into the atmosphere greater than the amount of oxygen used during aerobic respiration?


Which organisms in the picture release carbon dioxide? Which take it in?


In the above picture, which organisms release oxygen? Which take it in?


What is the name of the process during which green plants release oxygen?


What is the name of the process during which people and animals release carbon dioxide?

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