Unit A: Section 3.3 The Nitrogen and Phosphorus Cycle

1. Unit A: Section 3.3The Nitrogen and Phosphorus Cycle

2. The Nitrogen Cycle • http://www.youtube.com/watch?v=QEyd7TlyIJA&feature=related • Nitrogen occurs naturally in the atmosphere as Nitrogen gas (N2). • Air is about 79% nitrogen.

3. The Nitrogen Cycle • Why do animals need Nitrogen? • Nitrogen is needed for the construction of proteins and nucleic acids • Muscle tissue • Hair • Bones • Cell parts • DNA • RNA • In order for living organisms to be able to use this nitrogen, the two atoms must be separated (fixed), so they can easily combine with other elements to form usable compounds such as hydrogen and oxygen

4. Nitrogen and Plants • Nitrogen is a chemical that plants need to grow well. Plants get nitrogen through • Nitrates (NO3-): a group of nitrogen containing compounds that are readily absorbed by the roots of plants • Chlorophyll is the green pigment in plants • Need nitrates to produce it • The color of the leaves may inform you about nitrate level within the soil

5. Nitrogen Fixation • Is the process of changing free nitrogen so that the nitrogen atoms can combine with other elements to form compounds that organisms can use atoms • There are 2 main ways atmospheric nitrogen can be converted into useful forms. 1) Lightning 2) Legumes

6. Method #1 • Lightning can force nitrogen and oxygentogether to form nitrates • these will fall with precipitation and be absorbed by plant roots. • The plants will change these into their own proteins. • Animals eat the plants and reorganize those proteins into the ones they need.

7. Method #2 • Legumes are members of the bean family and include: • clover • Alfalfa… • Have nitrogen fixingnodules on their roots. • These can convert atmospheric nitrogen into nitrates. • Legumes can utilize atmospheric nitrogen.

8. Nitrogen and Decomposition • After an organism dies, it decays. • Ammonification: Decomposers convert nitrogen products (from tissues) into ammonia (NH3). • Ammonia will degrade into nitrites. (NO2) • Nitrites will degrade into nitrates(NO3). • The nitrates will now re-enter the cycle.

9. Nitrogen Cycle • Some bacteria will actually convert the nitrates back into atmospheric nitrogen. • Denitrifying bacteria. • These bacteria do not need oxygen -- anaerobic respiration. • The denitrification process speeds up when the soil is acidic or water-logged due to lack of oxygen. • Ex. bogs

10. Agriculture and Nutrient Cycles • As crops are harvested, much of the valuable nitrogen and phosphorous in these plants is removed and does not return to the field or orchard. • Fertilizers are materials used to restore nutrients and increase production from land. • The main nutrients in fertilizer is Nitrogen, Phosphorus, and Potassium. Sometimes Sulfur is used. • Fertilizer can be synthetically or naturally produced. • However too much fertilizer can be harmful to the environment.

11. High levels of nitrates may result in an increase in the amount of nitric acids in the soil. • Changes in the levels of acidity can affect all organisms living in the soil, including decomposer bacteria.

12. FERTILIZER IN ECOSYSTEMS • As spring runoff carries decaying plant matter and fertilizer-rich soil to streams and then lakes, the nutrients allow algae in the water to grow more rapidly in what is called an algal bloom. • When the algae die, bacteria use oxygen from the water to decompose them.

13. Because decomposers flourish in an environment with such an abundant food source, oxygen levels in lakes drop quickly, so fish and other animals may begin to die. • Nitrites can attach to the hemoglobin in blood, reducing its ability to carry oxygen to tissues. • The problem of nitrates in drinking water is especially serious for young animals, including human infants. • http://www.youtube.com/watch?v=XEZpo9uLIc0&feature=related • http://www.youtube.com/watch?v=ZsRSqPAL7Mc

15. Steps in the Nitrogen Cyle • Nitrogen fixation occurs • Plants can use the nitrogen-containing compounds • Animals then eat the plants and make larger compounds called proteins • Waste products are broken down into simpler compounds by decomposers to be used over again • Eventually nitrogen is released back into the atmosphere to begin the cycle all over. • http://www.mhhe.com/biosci/genbio/tlw3/eBridge/Chp29/animations/ch29/1_nitrogen_cycle.swf

16. The Phosphorus Cycle • Phosphorus is a nutrient required by all living things. • Component of bones and teeth • DNA • ATP (energy) • Phosphorus Cycle is simpler than the carbon or nitrogen cycles because it does not involve movement through the atmosphere. • http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::480::640::/sites/dl/free/0072879351/113987/0008.swf::Phosphorus%20Cycle

17. Two methods of Phosphorus recycling: • geological (abiotic)- long term • living organisms (biotic)- short term

18. Long Term Cycle • Phosphorus is found in bed rocks in the form of phosphate ions (PO4) combined with a variety of elements. • Phosphates are soluble in water and so can be dissolved out of rocks. • Dissolved phosphate can be carried by water from land to rivers than oceans. • Phosphate are absorbed by algae and other plants where they can enter food chains. • Marine animals use phosphate to make bones and shells. • When they die the hard remains form depositions on the ocean floor. • Covered with sediments it usually becomes rocks again ready to be brought to the surface.

19. Long Term Cycle

20. Short Term Cycle • Phosphates in water also enter the food chain through photosynthetic organisms • Plants are eaten by animals • Decomposition of dead organisms create soluble phosphates which are than again absorbed by plants

22. http://bcs.whfreeman.com/thelifewire/content/chp58/5802004.htmlhttp://bcs.whfreeman.com/thelifewire/content/chp58/5802004.html • http://www.youtube.com/watch?v=3iwL24oVpH4&feature=related