1. Systems & Interactions in Nature
Cycles in Nature

2. The Nitrogen Cycle
All living things need nitrogen to survive, but most organism’s cannot use nitrogen in its atmospheric form.
In the nitrogen cycle, nitrogen has is changed into forms that plants can use.
Nitrates and ammonia

3. The Nitrogen Cycle How nitrogen is changed
Most of the nitrogen gas is changed by bacteria in the soil or in nodules on the roots of some plants.
Some nitrogen gas is changed by lightning.

4. The Nitrogen Cycle How nitrogen is used
Plants use nitrogen in the soil to make proteins.
Animals get nitrogen by eating plants, or by eating other animals that eat plants.

5. The Nitrogen Cycle How nitrogen is returned to soil
Through animal wastes:
Solid waste contains nitrates
Liquid waste contains ammonia
When animals and plants die, bacteria released nitrates and ammonia through decomposition

7. The Carbon Dioxide-Oxygen Cycle
Carbon and oxygen is moved among plants, animals, and the environment.
All living organisms are involved in this cycle.

9. Carbon Dioxide-Oxygen
First, photosynthesis occurs:
Plants on land and in the water make their own food by changing the sun’s energy into food and taking in carbon dioxide from air and water
Oxygen is released into the air and water

11. Carbon Dioxide-Oxygen
All living organisms use the oxygen that was released for respiration (breathing).
They release carbon dioxide back into the atmosphere.

13. Carbon Dioxide-Oxygen
Carbon is also returned into the cycle when organisms die.
Some carbon is stored in the body until decomposition occurs and is used for food by plants and animals.
The rest is released as carbon dioxide into the air.

14. Carbon Dioxide-Oxygen
The carbon dioxide in the air is then taken in again for the process of photosynthesis, starting the process over.
The carbon underground could be turned into fossil fuels. The fossil fuels are then burned (combustion) and carbon dioxide is returned into the air.

15. Changing the Balance
The carbon dioxide-oxygen cycle was in balance for millions of years, but human influence has greatly impacted the cycle.
Our industrial activity releases excess amounts of carbon dioxide into the atmosphere.
Forests are cut down to meet other human needs (shelter, farms, etc.). There is a shortage of trees, so the excess of CO2 is building up in the air.
Too much CO2 is poisonous to animals and people.

16. Systems & Interactions in Nature
The Water Cycle

17. Water All living organisms need water to survive.
Plants take in water from the soil.
Most animals drink water from lakes or streams.
About 75% of Earth’s surface is water.
About 70% of the human body is water.

18. The Water Cycle
Water moves through the environment through the water cycle.

19. Evaporation
The heat of the sun changes water on Earth’s surface into water vapor

20. Condensation
The higher up the water vapor goes, the cooler the air gets.
The water vapor changes back into a liquid, forming a cloud.

21. Precipitation
Once many droplets join together to form clouds, the water may fall back to Earth.
Rain, snow, hail, sleet

22. Transpiration
This is the process where plants and animals put water back into the atmosphere.
Plants give off water through their stomata.
Animals release water vapor when they exhale.
Animals also release water through their urine.

23. Water Use
All of the water on Earth today is the same water that was here billions of years ago.
However, human activity contaminates the water with chemicals such as oil and road salt.