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Chapter 5.2 The Cycling of Materials Environmental Science Spring 2011 Describe short term and long term process of carbon cycle Identify one way that humans are affecting the carbon cycle List the three stages of the nitrogen cycle Describe the role that nitrogen-fixing bacteria play in the nitrogen cycle Explain how the excess use of fertilizer can affect the nitrogen and phosphorous cycle Objectives Carbon is an essential component of proteins, fats, and carbohydrates, which make up all organisms Carbon Cycle: process by which carbon is cycled between the atmosphere, land, water, and organisms The Carbon Cycle Carbon enters short term cycle in an ecosystem when producers (plants) convert carbon dioxide in the atmosphere into carbohydrates Consumers eat producers- consumers obtain carbon from carbohydrates The Carbon Cycle- short term cycle As consumers break down food during cellular respiration, some of carbon released back into atmosphere as carbon dioxide ◦ Organisms that make their own food through photosynthesis, release carbon dioxide during cellular respiration too The Carbon Cycle- short term cycle In the long term cycle: ◦ Carbon converted to carbonates- make up hard parts of bones and shells ◦ Carbonate deposits produce formations of limestone ◦ Limestone = carbon sink The Carbon Cycle- long term cycle Some carbohydrates converted to fats, oils, and storage molecules Carbon in these may be released into soil or air after an organism dies Can form deposits of coal, oil, natural as ◦ Fossil fuels The Carbon Cycle- long term cycle In the year 2000, vehicles were the source of one-third of all carbon dioxide emitted in the US Release carbon when burn fossil fuels Result in steady increase of carbon dioxide in the atmosphere ◦ Contribute to global warming: overall increase in Earth’s temperature Humans and Carbon Cycle Nitrogen cycle: process in which nitrogen is cycled between atmosphere, bacteria, and other organisms All organisms use nitrogen to build proteins, which are used to build new cells Nitrogen makes up 78% of the gases in the atmosphere ◦ Most organisms cannot use atmospheric nitrogen!! Nitrogen Cycle Nitrogen must be altered or fixed before organisms can use it Nitrogen-fixing bacteria: only organisms that can fix atmospheric nitrogen into chemical compounds ◦ Other organisms depend on these bacteria to supply nitrogen Nitrogen Cycle Nitrogen fixing bacteria live in nodules on the roots of plants called legumes ◦ Beans, peas, clovers ◦ Some live in soil Bacteria use sugars provided by the legumes to produce nitrogen containing compounds such as nitrates ◦ Excess nitrogen is released into the soil Nitrogen Cycle Plants that do not have these bacteria get their nitrogen from the soil Animals get nitrogen from eating plants or other animals Nitrogen Cycle Decomposers ◦ Break down wastes such as urine, dung, leaves, and other decaying plants and animals and return the nitrogen that these wastes contain to the soil ◦ After returned to soil bacteria transform a small amount of the nitrogen into nitrogen gas, which returns to atmosphere Nitrogen Cycle- decomposers Phosphorous Cycle: movement of phosphorous from the environment to organisms and then back to the environment Phosphorous is part of many molecules that make up cells Cycle rarely includes atmosphere because phosphorous rarely occurs as a gas ◦ Slow cycle Phosphorous Cycle Phosphorous entering soil and water: ◦ Rocks eroding: small amounts of phosphorous dissolve as phosphate in soil and water ◦ Added to soil and water when excess phosphorous is excreted in waste from organisms and when organisms die and decompose Phosphorous Cycle Phosphorous entering soil and water: ◦ Some phosphorous also washes off the land and ends up in ocean Phosphate salts are not soluble in water, so they sink to bottom of ocean, accumulate as sediment Plants absorb phosphates in the soil through their roots ◦ Animals absorb phosphates from plants Phosphorous Cycle People apply fertilizers Fertilizers contain nitrogen and phosphorous Fertilizer and Nitrogen and Phosphorous Cycles If excess used, fertilizer can enter terrestrial and aquatic ecosystems ◦ Causes overabundant growth of algae: algae bloom Can deplete ecosystem of important nutrients such as oxygen Fertilizer and Nitrogen and Phosphorous Cycles Burn fuel nitric oxide released into atmosphere Nitric oxide can combine with oxygen and water vapor to form nitric acid ◦ Contributes to acid precipitation Acid Precipitation Create a book outlining each of the cycles: ◦ Carbon cycle- include atmospheric CO2, Photosythnesis, Respiration, Combustion, Natural gases and Coals, Decomposition, Limestone ◦ Nitrogen cycle- atmospheric nitrogen, runoff, nitrogen-fixing bacteria, bacteria in soil and water, lightning ◦ Phosphorous cycle- rain, phosphate mining, fertilizer, runoff, phosphate in water, decomposition, phosphate in soil, phosphate in rocks Assignment
