2/11/16. Materials in ecosystems are constantly reused Three cycles: The Carbon Cycle The Nitrogen Cycle The Phosphorus Cycle

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1 Materials in ecosystems are constantly reused Three cycles: The Carbon Cycle The Nitrogen Cycle The Cycle Carbon is essential in proteins, fats, and carbohydrates, which make up all organisms Carbon cycle a process by which carbon is cycled between the atmosphere, land, water and organisms Carbon enters an ecosystem when producers convert carbon dioxide in the atmosphere into carbohydrates Consumers get carbon from producers and release as CO 2 * Carbon ENTERS biotic environment through: Photosynthesis: changes light energy to chemical energy Carbon RETURNS to atmosphere by: 1. Respiration CO 2 2. Decomposition / Decay 3. Burning * Carbon Cycle and Humans: 1. Removal of photosynthesizing plants 2. Combustion of fossil fuels 1

2 Fossil fuels are stored carbon left over from bodies of plants and animals that died millions of years ago When we burn fossil fuels, we release carbon into the atmosphere Carbon returns to atmosphere as CO 2 6 billion metric tons of carbon a year are released into the atmosphere as carbon dioxide ½ of this carbon stays in atmosphere Increased levels of carbon dioxide may contribute to global warming Global warming an overall increase in the temperature of the Earth Scientists estimate that over a billion tons of carbon dioxide dissolves into the ocean Atmosphere is 78% nitrogen All organisms need nitrogen to build proteins (which are used to build new cells) Can t use atmospheric nitrogen Has to be altered or fixed Can only be done by nitrogen-fixing bacteria Nitrogen-fixing bacteria are a crucial part of the nitrogen cycle A process in which nitrogen is cycled between the atmosphere, bacteria, and other organisms Bacteria take nitrogen from gas in the air and transform it into molecules that living things can use 2

3 Live within nodules on the roots of plants called legumes (some live in the soil) Beans, peas, clover Extra nitrogen is released into soil Plants get nitrogen from their nitrogen-fixing bacteria or the soil Animals get nitrogen from eating the plants Fixation Nitrogen means: Cycle to chemically Nitrogen change in the a compound atmosphere into another similar compound e.g. N 3 to NH 3 Nitrogen consumption Decomposing dead matter Fixation by bacteria, or lightning Denitrifying bacteria Nitrogen in the soil Nitrogen moves between atmosphere and living things Decomposers break down waste and return nitrogen to the soil Without decomposers, most nitrogen would be stored in waste Nitrogen stays within ecosystem, cycling between organisms and the soil and is constantly reused * Nitrogen RETURNS to soil by: 1. decomposition of once living things - done by fungi and bacteria 2. exists in soil as nitrate (NO 3- ), nitrite (NO 2- ), and ammonia (NH 3 ) * Nitrogen returns to atmosphere by: 1. denitrifying bacteria * Nitrogen Cycle and Humans: 1. Nitrogen required for genetic materials (DNA, RNA, amino acids) 3

4 is an element that is part of many molecules that make up cells Plants get from soil and water Animals get from eating plants cycle The movement of phosphorus from the environment to organisms and then back to the environment Slow cycle Doesn t occur in atmosphere is rarely a gas stored in rocks Detritivores Cycle are: organisms that obtain nutrients by feeding off decomposing plant and animal matter (inc. faeces) released by weathering decomposed by detritivores in the soil consumed by animals absorbed by plants Rocks erode, small amounts of phosphorus dissolve as phosphate in soil and water Plants absorb phosphates is also added by dead organisms and waste also washes off land and ends up in ocean, sink to bottom 1. Leaching: water dissolves phosphates in rocks and carries to lake, stream, etc. 2. Dissolved phosphate: used by plants and passed through food chain 3. Animals return phosphorus to environment by: * excretion * death and decay * Cycle and Humans: 1. Phosphates mined for fertilizers returns P to soil 2. Erosion: P in soil and rocks washed away into water systems 4

5 Fertilizers are used to stimulate and maximize plant growth and contain phosphorus and nitrogen The more phosphorus and nitrogen available to a plant, the bigger and faster it will grow Fertilizer is bad too can run off into waterways and cause overpopulation of algae When fertilizer runs off into the waterways, it causes an overgrowth of algae Algal blooms are dense visible patches of algae that occur near the surface of water They can deplete an aquatic ecosystem of important nutrients We affect the nitrogen cycle every time we burn coal, wood, or oil Nitric oxide is a harmful gas released when burning Combines with oxygen and water vapor to form nitric acid Can dissolve in rain or snow and cause acid precipitation 1. Describe the three stages of the carbon cycle. 2. Describe how the burning of fossil fuels affects the carbon cycle 3. Explain how the excess use of fertilizer affects the nitrogen cycle and phosphorus cycle 4. Explain why the phosphorus cycle occurs more slowly than both the carbon cycle and nitrogen cycle. 5. Write a short paragraph that describes the importance of bacteria in the carbon, nitrogen, and phosphorus cycles. What role does bacteria play in each cycle? 6. What is one way that a person can help reduce the level of carbon dioxide in the atmosphere? Can you think of more than one way? 5