Take a Deep Breath — The Oxygen Cycle
Living things need oxygen to survive. We inhale oxygen and exhale carbon dioxide. This is called respiration. Plants then take that carbon dioxide, convert it into carbohydrates, and release oxygen. Then we use that oxygen, and the cycle continues. Animals, plants, and even bacteria also use oxygen. When plants and animals die and decompose, that process uses oxygen too. Oxygen is used when you burn a fire. Even rusting metal uses oxygen. (This is called oxidation.) Oxygen is needed for processes all over the planet! With so many living things breathing all the oxygen on Earth, you would think we might run out, but luckily more oxygen is being made all the time in the oxygen cycle.
Create Your Own Water Cycle
If you have ever looked at a terrarium, you have seen a tiny water cycle in action. You can create this effect easily yourself.
Take a small, empty jar with a lid. Line the bottom with small pebbles and then about an inch of soil.
Then go out in the woods and dig up a small patch of plants. It can be any plants — weeds are fine. Include a little moss or not, just make sure you have a bunch of green plant life.
Water your plant until you can see the water covering the pebbles at the bottom.
Then put on the lid and set it in the sun.
Watch your terrarium. Within a day or two, the water will condense on the sides of the jar. From this point forward you will not have to water your terrarium. It has its own water cycle!
The oxygen cycle never stops, but where does oxygen come from? Mostly oxygen comes from photosynthesis. Both plants on land and phytoplankton (tiny, microscopic plants floating on the surface of the ocean) use photosynthesis to make energy. They also make oxygen! Photosynthesis is a process where the organism uses sunlight, carbon dioxide, and water to make oxygen and sugar. Thank goodness for green plants and other photo synthesizers!
