1. C1-2 NATURAL CYCLES
Mr. Ratliff

2. A. Earth’s Resources Earth’s ecosystems depend on energy from the sun
Abiotic materials are used over and over again because living things return them to the environment in cycles

3. B. Water Cycle Water cycle—movement of water through earth’s ecosystem
Precipitation—water that returns to earth in the form of snow, rain, hail, sleet, etc.
Transpiration—excess water that is released into the atmosphere by plants—release over 99% of water back into air

4. Evaporation—as water heats up changes from liquid to water vapor and rises into the atmosphere
Condensation—water vapor cools and goes back to a liquid—water droplets join dust to form clouds
Ground water—when precip. soaks into the ground—water is taken to the ocean or another body of water

5. C. Carbon Dioxide-Oxygen Cycle CO2-O2
Plants need CO2 to make food
Animals and plants both need O2 for respiration (break down food to release energy)

6. CO2-O2 cycle—flow of CO2 and O2 through Earth’s ecosystems
Phytoplankton—one-celled protists that make food, then give off much of the O2 in the atmosphere
Air is 21% O2 and .03% CO2

7. D. Nitrogen Cycle --N2
Nitrogen is needed in proteins—builds muscles and bones
N2 is 78% of air
Nitrogen cycle—movement of N2 through Earth’s ecosystems

8. Nitrogen needs to be changed for our use—2 ways that happens
Lightning releases N2—comes to earth with rain
Bacteria on legumes returns N2 to the soil to be used by plants
---bacteria in the soil returns N2 back to air as it decomposes organisms