1. Matter is classified as either organic or inorganic. Organic matter always contains carbon and hydrogen, although other elements may also be present. Inorganic matter does not contain both carbon and hydrogen, and is usually of mineral origin. Photosynthesis is the process whereby plants use the Sun’s energy to convert carbon dioxide and water into carbohydrates and oxygen. Cellular respiration is the reaction between carbohydrates and oxygen that produces energy, carbon dioxide, and water. Cycling of Organic and Inorganic Matter 4.1 VOCABULARY organic inorganic photosynthesis cellular respiration Organic compoundsInorganic compounds carbohydrates proteins nucleic acids (e.g., DNA) lipids water salts ammonia oxides

2. The Carbon Cycle 4.2 VOCABULARY carbon reservoirs carbon sinks fossil fuels carbon source carbon cycle greenhouse gases greenhouse effect oxygen cycle aerobic respiration anaerobic respiration fermentation The carbon cycle and the oxygen cycle are connected through the processes of photosynthesis and cellular respiration. Carbon dioxide in the atmosphere acts as a greenhouse gas by trapping heat from the Sun.

3. The Nitrogen Cycle 4.3 VOCABULARY nitrogen cycle nitrogen fixation legumes nitrate nitrification denitrification The nitrogen cycle moves from nitrogen fixation to nitrification to denitrification. Nitrogen fixation is the process whereby nitrogen gas is “fixed” or combined with hydrogen to produce ammonia (NH 3 ). Nitrification the process that produces nitrate from ammonium. Denitrification is the process of converting ammonia and nitrate back to nitrogen gas.

4. The Phosphorus Cycle 4.5 VOCABULARY phosphorus cycle phosphate ions mycorrhizae Phosphorus does not have an atmospheric form. The phosphorus cycle exists as a short and long cycle. The short cycle occurs when organisms die and decompose, making their phosphorus available to producers. The long cycle describes the geological path of phosphorus.

5. Nature’s Recycling Programs There is a finite amount of matter on Earth. Matter is classified as organic or inorganic based on what elements it is composed of. 4 CHAPTER

6. Nature’s Recycling Programs The matter that makes up nutrients for organisms is cycled between biotic and abiotic components of ecosystems. Most notable are the carbon, nitrogen, and phosphorus cycles. 4 CHAPTER

7. Nature’s Recycling Programs Activity Use your knowledge of photosynthesis and cellular respiration to explain, using words and pictures, why we don’t run out of oxygen if there is a finite amount in Earth’s atmosphere. See pages 87 and 89 in the textbook for help if needed. 4 CHAPTER

8. Nature’s Recycling Programs 4 Key Ideas Matter is classified as organic or inorganic. Nutrients cycle between biotic and abiotic components of ecosystems. CHAPTER