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Ecosystems and Their Interactions Chapter 6 Lesson 6.2 PA Academic Standards for Environment & Ecology Standard 4.6.10.B • • • Explain how cycles affect the balance in an ecosystem. Describe an element cycle and its role in an ecosystem. Explain the consequences of interrupting natural cycles. Learning Objectives • Students will describe an element cycle and its role in an ecosystem. • Students will explain the consequences of interrupting natural cycles. Theme Outline Lesson 6.2 • • • • Cycles in an Ecosystem The Water Cycle The Carbon Cycle The Nitrogen Cycle Cycles in an Ecosystem • Earth is a closed system • Matter continuously cycles throughout different parts of an ecosystem Major Cycles Three major cycles • Water Cycle • Carbon Cycle • Nitrogen Cycle Major Cycles Three major cycles • Water Cycle • Carbon Cycle • Nitrogen Cycle The Water Cycle Worldwide Water Supply Water water everywhere but… • Covers 70% of the Earth’s surface. • Most living things are primarily water. • Humans are ~65% water. … the Earth’s water supply is finite • Finite – a fixed amount. Which means … The same amount of water that was on Earth when the dinosaurs were around, still exists today!!! The Water Cycle Processes at work… • Evaporation • Liquid water to water vapor • Condensation • Water vapor cools and condenses into clouds as water droplets • Precipitation • Water droplets fall to the Earth as rain, sleet, hail, or snow • Runoff • Water runs off into nearby streams, rivers, lakes, or enters the groundwater • Infiltration/Percolation Why is water such an important substance? • There is less than 1% of freshwater available on the surface of the Earth for drinking, bathing, and cooking. • Human activities have greatly impacted quality of freshwater supplies. Example: pollution from chemical spills, poor wastewater treatment, agricultural runoff, and septic tank failure Water Quality Concerns • Agricultural runoff contains a host of potentially harmful chemicals and sediments that can easily enter waterways. • In Pennsylvania, access to potable drinking water is not an issue for most. • However, in other parts of the world, limited access to safe potable water is a major concern for populations living along many waterways. Major Cycles Three major cycles • Water Cycle • Carbon Cycle • Nitrogen The Carbon Cycle Why is carbon important anyway? • Carbon is the building block for life. • Carbon is the basis for all organic life. • Carbon is essential for making … DNA Proteins Fats Carbohydrates Where else is carbon found? • Carbon Dioxide (CO2) • This greenhouse gas helps maintain heat in the Earth’s upper atmosphere. • Carbon reservoirs • Oceans • Atmosphere • Rocks The Carbon Cycle… simplified The Carbon Cycle: Rock and Fossil Fuel Formation Organic matter Marine shells Rocks Minerals Wetland Material Organic Matter Fossil Fuels Major Cycles Three major cycles • Water Cycle • Carbon Cycle • Nitrogen The Nitrogen Cycle Nitrogen • Composes ~79% of the atmosphere • The atmosphere is a major nitrogen reservoir. • However, most of the nitrogen in the atmosphere is not in a usable form so it can not be used by plants and animals. Nitrogen is necessary for making… • • • • DNA Proteins Amino Acids Chlorophyll The Big 3… N2 Atmosphere NO3 NO2 Nitrates Nitrites Four major processes… 1) Nitrogen fixation 2) Decay 3) Nitrification 4) Denitrification Types of Nitrogen Fixation Atmospheric fixation Lightning in the atmosphere breaks up nitrogen molecules and when combine with oxygen they form nitrates. N2 NO3 Atmospheric Nitrogen Nitrates Industrial fixation Combines nitrogen in the atmosphere with hydrogen to form ammonia Occurs under pressure and high temperatures (~600oC) Product used as fertilizer in agriculture N2 NH3 Atmospheric Nitrogen Ammonia Fertilizer Labels Biological fixation Plants and bacteria convert atmospheric nitrogen into ammonia N2 NH3 Atmospheric Nitrogen Ammonia Soybeans/Legumes Nitrogen fixing bacteria Decay • Nitrogen cycles through food chains like other elements. • Nitrogen is found in excreted wastes from animals. • Microorganisms break down excretions and dead animals to form ammonia. Nitrification A process that converts nitrogen, in various forms, into more usable forms of nitrogen that can be taken up through the roots of plants. Convert organic nitrogen into nitrites and nitrates. NH3 NO3 Ammonia Nitrates Denitrification A process preformed by bacteria that live deep in soils and aquatic sediments under anaerobic conditions. What does it mean when we say anaerobic? NO3 N2 Nitrates Atmospheric Nitrogen The Nitrogen Cycle Changes to Ecosystems • Occur more frequently in some ecosystems than others • Cycles and processes continue to cycle materials through ecosystems, even after disturbances • Ecosystems change in order to meet the conditions present Example: regrowth of a forest after forest fires destroy forest floor (organic matter)