1. How Does Nature Reuse Materials?
How Natural Materials Are Reused

2. Natural Cycles
Many materials on Earth are used and then reused by living things.
The materials dissolve in rivers and lakes or become part of the soil.
When an animal drinks water, it gets some of the materials it needs.
Animals also get materials they need by breathing and eating.
Animals release materials into the environment with their wastes.

3. Plants get the materials they need from the soil and from the air.
Plants release some materials into the environment during photosynthesis.

4. When plants and animals die, they release some materials into the environment.
Materials that end up in landfills, take longer to return to the soil.

5. The Nitrogen Cycle All living organisms need nitrogen.
Plants make proteins from nitrogen in the soil.
Animals make proteins when they eat plants or animals that eat plants.

6. The Earth’s atmosphere is about 78% nitrogen but organisms can’t use it in that form.
In the nitrogen cycle, the nitrogen must be FIXED or changed into forms that plants and animals can use.
These forms are nitrates and ammonia.
Bacteria in the soil and on the roots of plants fix most of the nitrogen gas.
Lightning will also fix small amounts of nitrogen.

7. N cycle continued
Nitrates and ammonia are returned to the soil in two ways.
First, they are deposited with animal wastes. Solid wastes deposit nitrates; urine deposits ammonia.
When plants and animals die, bacteria release nitrates and ammonia from decaying protein.

8. Changing the Balance
For hundreds of millions of years the carbon-oxygen cycle stayed in balance.
Since the Industrial Revolution, human activity has started to change the balance.
Industry or factories, use large amounts of fuel and energy. As more factories were built, more energy was needed.
Factories, heating systems, cars, trucks, airplanes all need and burn fuels.
Burning fuels adds carbon dioxide into the air.

9. Adding carbon dioxide into the air is a BIG problem.
Carbon dioxide is poisonous to animals, including humans.
Cutting down trees is double trouble– you deplete the number of forests AND you lose the oxygen they make.
As a result, carbon dioxide continues to build up in the air.