1. Cycles Unit 4 Section 3

2. Water Cycle Water constantly moves between the oceans, atmosphere and the land It can be inside or outside of living organisms

3. Steps of the water cycle Evaporation: – Water evaporates or enters the atmosphere as a gas called water vapor from bodies of water or plants Condensation: – The water vapor in the atmosphere condenses into tiny droplets that form clouds

4. Steps of the water cycle continued….. Precipitation: – When the droplets in the clouds become large enough they fall to the earth as precipitation – Example: rain, sleet, snow Runoff: – Precipitation that flows along the surface of the land into a river or stream

5. Steps of the water cycle continued….. Groundwater: – Precipitation can be absorbed into the ground becoming groundwater – If groundwater goes deep enough it can become part of the underground reservoirs – Groundwater enters plants through their roots or flows into bodies of water Water re-enters the atmosphere through evaporation and the process starts again

7. Carbon cycle Carbon is a major component of all organic (relating to an organism) compounds – Example: carbohydrates, lipids, proteins and nucleic acids

8. Steps of the Carbon Cycle Geological activity: – Carbon is found in reservoirs in the biosphere – A mineral found in animal skeletons and rocks – Marine sediments that have animal skeletons in them are turned into rocks – This releases carbon dioxide into the atmosphere

9. Steps of the carbon cycle continued….. Photosynthesis: – Carbon dioxide from the atmosphere is taken up by producers to make food – Consumers eat producers and release carbon dioxide into the atmosphere through cellular respiration

10. Steps of the carbon cycle continued….. Fossil fuels: – Examples: coal, oil and natural gas – When they are burned they give us energy they release carbon dioxide into the atmosphere – Dead matter eventually decomposes into fossil fuels Ocean and rainwater – Dissolved carbon dioxide is found in the ocean and rainwater

12. Nitrogen Cycle All organisms need nitrogen to make amino acids (proteins) and nucleic acids (DNA and RNA) Nitrogen exists as a gas in the atmosphere (N 2 ) Nitrogen compounds such as ammonia (NH 3 ), nitrate ions (NO 3 - ) and nitrite ions (NH 2 - ) are found in the soil They can also be found in wastes and decomposing organisms

13. Nitrogen cycle continued…… Dissolved nitrogen can be found in oceans and large bodies of water Steps of the nitrogen cycle: – Atmospheric nitrogen: nitrogen gas in the atmosphere is the most common kind of nitrogen – Only certain kinds of bacteria can use this gas – These bacteria convert the nitrogen gas to ammonia so that producers can use it – Some nitrogen gas can be changed by lightning

14. Steps of the nitrogen cycle continued…… Producers use nitrogen in the soil to make proteins and nucleic acids Consumers eat producers and use nitrogen to make their own proteins and nucleic acids Decomposers release ammonia, nitrates and nitrites from wastes and dead organisms – Producers then use these compounds

15. Steps of the nitrogen cycle continued….. Nitrogen fixation – bacteria convert nitrates into nitrogen gas These bacteria live in the soil Humans add nitrogen to the cycle by using fertilizers Runoff carries excess fertilizer into surface water or groundwater