1. Natural Cycles C22 – C35 1

2. Natural Cycles of the Earth There are 3 important cycles to study in this unit: 1-THE WATER CYCLE 2-THE CARBON CYCLE 3-THE NITROGEN CYCLE 2

3. The Water Cycle O Most of Earth’s water is in the ocean. O The water cycle is the movement of water through Earth’s ecosystems. Water travels to all the parts of the environment. 1- Evaporation 2- Condensation 3- Precipitation 4- Transpiration 5- Ground Water 6- Runoff 3

4. Evaporation O The water cycle depends on energy from the sun to move water around the Earth. O This causes water in lakes, ponds, rivers, and oceans to change from liquid water to water vapor. 4

5. Condensation O Water vapor changes from a gas to a liquid in condensation. When water vapor condenses on dust particles in the air, clouds form. 5

6. Precipitation O Precipitation returns the water to Earth’s surface. O Water vapor does not contain any minerals, so precipitation is fresh water. O Rain O Sleet O Snow O Hail 6

7. Transpiration O Plants lose water to the air in a process called transpiration. O This is similar to ‘sweating’ in humans. 7

8. Ground Water O Some precipitation soaks into the ground. O Some water flows underground until it reaches the ocean or another body of water. 8

9. Runoff O Some precipitation flows along the surface of the land. In time, it reaches the ocean, lakes, rivers, and streams. 9

10. The Carbon Cycle O Living things are largely made up of carbon. O Plants use carbon dioxide when they make food in photosynthesis. O The carbon cycle is necessary for plant growth. O The flow of carbon as a solid, liquid and a gas through Earth’s ecosystems is the carbon cycle. O See pp. C24 – C25. 10

11. The Nitrogen Cycle O The Nitrogen Cycle moves nitrogen through the ecosystem. O Cells are made of protein, protein is made of nitrogen. O Nitrogen goes up into the air through decomposition of plants and animals. O See p. C26. 11

12. Reusable Resources O Reusable resources can be used again and again. O Examples are water, carbon dioxide, oxygen and nitrogen. O Aluminum is reusable if it is recycled. 12

13. Renewable Resources O Renewable resources can be replaced within a human life span. 13

14. Nonrenewable Resources O Resources that cannot be replaced within a human life span. Once used, they are gone forever. O Coal, oil, gas, electricity, and minerals. 14

15. Humans Can Alter Ecosystems O One of the factors affection Earth’s ecosystems is human activity. O Burning fossil fuels causes pollution, which is cycled through the ecosystem. O Acid Rain damages stone and metal structures, crops, leaves, stems, plants and is soaked into roots. 15