1. Cycles of Matter Chapter 23-2

2. Matter Recycled in ecosystems Includes water, oxygen, nitrogen, and many other substances Most important cycles of matter are: water cycle, carbon-oxygen cycle, and nitrogen cycle

3. Water Cycle Continuous process Processes of evaporation, condensation, and precipitation make up the water cycle

5. Evaporation Molecules of liquid water absorb energy and change to a gas state Water evaporates from Earth’s surface and forms water vapor, a gas, in the atmosphere

6. Condensation A gas changes to a liquid When water in the atmosphere cools, it turns back into tiny droplets of liquid water As more water vapor condenses, the drops grow larger and heavier

7. Precipitation The heavy drops fall back to Earth as precipitation Rain, snow, sleet, or hail

8. Carbon-Oxygen Cycle Carbon is the building block for the matter that makes up the bodies of living things Producers take in carbon dioxide during photosynthesis Producers use the carbon to make other carbon-containing molecules (sugars and starches)

10. Consumers obtain energy from these molecules by breaking them down into simpler molecules Consumers release water and carbon dioxide as waste products of the process At the same time, producers release oxygen

11. Nitrogen Cycle Nitrogen is a necessary building block in the matter that makes up living things Most organisms cannot use “free” nitrogen gas in the air Can only use it when it has been fixed or combined with other elements

12. Nitrogen fixation is the process of changing nitrogen gas into a usable form Performed by certain kinds of bacteria that live in bumps called nodules on the roots of certain plants Decomposers break down these complex compounds in animal waste and dead organisms

13. Decomposition returns simple nitrogen compounds to the soil Certain types of bacteria break down nitrogen completely, and release free nitrogen back into the air, and the cycle starts again