1. Cycles of Matter
Chapter 23
Section 2

2. Recycling Matter
Matter cycles through an ecosystem over and over. Matter in an ecosystem includes water, oxygen, carbon, nitrogen, and many other substances.
Matter is made up of tiny particles called atoms. Combination of two or more atoms chemically bonded together are called molecules.

3. Water Cycle
Continuous process by which water moves from Earth’s surface to the atmosphere and back.
The processes of evaporation, condensation, and precipitation make up the water cycle.

4. Water Cycle
Evaporation
Condensation
Precipitation
Surface Runoff

5. Evaporation
Process by which molecules of liquid water absorb and change to the gas state is called evaporation.
The energy for evaporation comes from the sun

6. Condensation
Process by which a gas changes to a liquid is called condensation.

7. Precipitation
When more water vapor condenses, the drops of water in the cloud grow larger and heavier. Eventually the heavy drops fall back to Earth as a form of precipitation.

8. The Carbon and Oxygen Cycles
Two other chemicals necessary for life are carbon and oxygen.
Plants take in carbon dioxide.
Plants use carbon to make sugar molecules.
Plants produce oxygen
Animals take in oxygen
Animals break down sugar molecules
Animals releases carbon dioxide
Plants take in carbon dioxide

9. The Carbon and Oxygen Cycles

10. Nitrogen Cycle
Most organisms can use nitrogen only once it has been “fixed” or combined with other elements to form nitrogen-containing compounds.

11. Nitrogen Fixation
Process of changing free nitrogen gas into a usable form of nitrogen is called nitrogen fixation.
Most nitrogen fixation is performed by certain kinds of bacteria.
Some of these bacteria live in bumps called nodules on roots of certain plants.
These plants, known as legumes, include clover, beans, peas, alfalfa, and peanuts.

12. Nitrogen Fixation
The relationship between the bacteria and the legumes is an example of mutualism.
The bacteria feed on the plant’s sugars, and the plant is supplied with nitrogen in a usable form.

13. Nodules