1. Nitrogen Cycle Chapter 3 Section 3.4 continued

2. Nitrogen Cycle 1. Living things require nitrogen to make amino acids, which are used to build proteins and DNA. 2. Nitrogen Gas (N 2 ) makes up 78% of Earth’s atmosphere. However this is NOT a usable form for organisms. 3. Nitrogen can cycle out of the atmosphere with assistance from lightning, specialized bacteria, or human technology

3. 4. Usable Forms include ammonium, nitrite ions, and nitrate ions. 5. Substances such as ammonium (NH 4 ) are found in soil, in the wastes produced by many organisms, and in dead and decaying organic matter. 6. Dissolved nitrogen exists in several forms in the ocean and other large water bodies

4. The Nitrogen Cycle

5. How does the nitrogen get fixed to a usable form? Nitrogen gas is the most abundant form on Earth, only certain types of bacteria that live in the soil and on the roots of plants can use this form directly. [nitrogen fixation] Bacteria nitrates ammonia consumers producers decomposers

6. 1.Most plants can only use nitrogen in the form of ammonia (NH 3 ) 2.Organisms rely on nitrogen fixing bacteria to convert N 2 gas into ammonia (NH 3 ), which plants then absorb and use to make proteins. 3.These bacteria live in the soil and on the roots of some plants  soybeans, clover, and other legumes (peas, bean plants, peanuts)

7. Recycling Nitrogen 1.Bacteria in the soil take up ammonia and oxidize it into nitrites (NO 2 - ) and then into nitrates (NO 3 -). This process is called nitrification. 2.Plants use nitrates to make amino acids (building blocks of proteins). These are passed along the food chain. 3.Nitrogen gas is returned to the atmosphere by anaerobic bacteria through a process called denitrification.

8. What is our affect on the nitrogen cycle? 1. Humans add nitrogen through the manufacture and use of fertilizers. 2. Excess fertilizer is often carried into surface water or groundwater by precipitation. 3. Runoff adds nitrogen to water sources like ponds, streams, rivers, and lakes. Fertilizer ingredients

9. 4. When we burn fields, we force the nitrogen from the soil to enter the atmosphere. 5. When we burn fossil fuels we add nitric oxide (NO) into the air causing smog. 6. (NO) mixes with oxygen to form nitric dioxide (NO 2 ) leading to acid rain.