1. Oxygen Cycle  Constituent of water  Forms 21% of gases found in the atmosphere  Required for respiration for all biotic organisms  Necessary for decomposition of organic waster  Dissolved oxygen is essential for aquatic life

2. Overview of Oxygen Cycle Plants release oxygen into the atmosphere as a by-product of photosynthesis Plants release oxygen into the atmosphere as a by-product of photosynthesis Animals take in oxygen through the process of respiration Animals take in oxygen through the process of respiration Animals break down sugars and food Animals break down sugars and food Carbon dioxide is released through respiration Carbon dioxide is released through respiration

4. Photosynthesis  The process by which light energy is converted to chemical energy

5. Weathering  Physical and chemical process in which solid rock exposed at earths surface is changed to separate solid particles and dissolved materials

6. Respiration & Decay  Mechanisms in which animal life and bacteria consume oxygen and release carbon dioxide

7. Burial Photolysis Burial Photolysis  The oxygen left inside of people after they have been buried in the ground gets absorbed by the soil.  The chemical decomposition of materials under the influence of light

8. Plants  The oxygen cycle starts off in plants.  Plants use photosynthesis to produce carbohydrates and oxygen  Plants “breathe” in carbon dioxide and “breathe” out oxygen

9. Water  When the water in a steam enters a pond, microorganisms in the pond begin to break down organic matter, consuming oxygen in the process.

10. Organism  Last in the cycle are the organisms  Their role in the cycle begins with carbon dioxide in the atmosphere.  Animals breathe that oxygen and both plants and animals use the sugars for energy.