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Ecosystems consists of all the organisms living in a community as well as all the abiotic factors with which they interact. What is missing from this food chain? decomposers Energy can be neither created nor destroyed. It can only be transformed to another form. This is called the law of conservation of energy. In what way is this food web more realistic than the food chain? The food web incorporates consumers that feed at multiple trophic levels Primary Producers • Who are the primary producers of most terrestrial ecosystems? • Plants • Who are the primary producers of most aquatic ecosystems? • Microscopic algae and bacteria (phytoplankton), and multicellular algae and aquatic plants. Consumers • Herbivores - primary consumers • Carnivores - secondary consumers • Omnivores - can feed at multiple trophic levels Decomposers • What organisms are decomposers in most ecosystems? • Fungi and Bacteria • What do the decomposers do? Primary Productivity • The energy budget of an ecosystem depends on its primary productivity. • What is gross primary productivity? (GPP) GPP represents energy available to consumers in an ecosystem. What is Net Primary Productivity? (NPP) NPP = GPP - R Net Primary Productivity • Why is NPP a more useful measurement than GPP? How is it that the open ocean has low net productivity yet accounts for most of the Earth’s total productivity? Limiting Factors • What sort of factors will limit productivity? • Light intensity • Water • Inorganic nutrients such as nitrogen and phosphorus. • CO2 Energy Partitioning Within the Food Chain Energy may also be expressed as kilocalories (kcal) What does this number represent? Energy Partitioning Within the Food Chain This is also called biomass The energy available for the next trophic level. Typically the amount of energy that is eaten by an organism is not all converted into waste, growth, and used for cellular respiration. What happens to the rest? Energy Partitioning Within the Food Chain Total Energy Output: Respiration Heat Loss Waste This is also called biomass The energy available for the next trophic level. Ecological Efficiency • How much of energy is actually available to the next trophic level? • Usually around 10% is available • Why is it that we don’t see 6th order consumers? An ecological pyramid is a diagram that shows the relative amounts of energy or matter contained within each trophic level in a food chain or food web. Which has more energy, a quarter pound of salad or a quarter pound of beef ? How can the producers in the English Channel support the consumers in this ecosystem? Answer: The primary producers have a short life span and also reproduce rapidly How many individuals are supported at the top level of this ecosystem? Chemical Cycling Biogeochemical Cycles/Cycles of Matter – the way in which elements, chemical compounds, and other forms of matter are passed from one organism to another and throughout the biosphere. ** The numbers represent water flow in billion billion grams per year Transpiration in Leaves Open and Closed Stomata in a Spider Plant Leaf Humans Affect the Water Cycle by Changing Land Use: • Reduced vegetation (deforestation, cultivation, etc.) reduces precipitation retained in soil and increases amount that runs off. • Groundwater pumping depletes aquifers, brings water to surface where it evaporates. • Climate warming will melt ice caps and glaciers and cause sea level rise and increased evaporation. Water vapor is a greenhouse gas. Review of the Water Cycle: http://studyjams.scholastic.com/studyjams/jams/science/ecosystems/water-cycle.htm http://www.epa.gov/ogwdw/kids/flash/flash_watercycle.html Carbon is a key ingredient in the tissues of living things. What are three large reservoirs where carbon is found around the earth? In what process do plants use carbon dioxide? Human Activities Affect the Global Carbon Cycle: • Runoff brings carbon to aquatic ecosystems. • Deforestation and fossil fuel burning increase atmospheric CO2. • Atmospheric CH4 is increased through livestock production, rice cultivation, and water storage in reservoirs (microbes in water-logged soils produce CH4). Review of the Carbon Cycle: http://studyjams.scholastic.com/studyjams/jams/science/ecosystems/carbon-cycle.htm http://bcs.whfreeman.com/thelifewire/content/chp58/5802002.html (conversion to organic forms) Why do organisms require nitrogen? Nitrogen fixation occurs when soil bacteria convert N gas into ammonia at their roots. Denitrification releases N gas back into the atmosphere by a different type of bacteria. Human Activities Affect the Nitrogen Cycle: • Burning fossil fuels, rice cultivation, and raising livestock releases oxides of nitrogen to the atmosphere. • These oxides contribute to smog and acid rain. • Humans fix nitrogen by an industrial process to manufacture fertilizer and explosives. Review of the Nitrogen Cycle: http://bcs.whfreeman.com/thelifewire/content/chp58/5802004.html http://www.biology.ualberta.ca/facilities/multimedia/uploads/ecology/ncycle.html http://studyjams.scholastic.com/studyjams/jams/science/ecosystems/nitrogen-cycle.htm Concept 46.3 Certain Biogeochemical Cycles Are Especially Critical for Ecosystems • Topsoil and dissolved nitrates are lost from farm fields and deforested areas by wind and water runoff. • The nitrates are deposited in aquatic ecosystems and result in eutrophication— increased primary productivity and rapid phytoplankton growth. Decomposition of the phytoplankton can deplete oxygen; other organisms cannot survive, and dead zones form offshore in summer. The Experimental Eutrophication of a Lake What does the loss of nitrates from the deforested ecosystem tell you about the water, and about how nitrates are normally maintained in the ecosystem? Review of the Phosphorus Cycle: http://nortonbooks.com/college/biology/animations/ch37a03.htm http://www.sumanasinc.com/webcontent/animations/content/phosphorouscycle.html For which macromolecules do organisms need phosphorus? Plants absorb phosphorus from the soil or from water. What is going on in this picture? We’ve Changed Our Tune Erosion of Earth’s Ozone Shield: The Ozone Hole Over the Antarctic Erosion of Earth’s ozone shield: Thickness of the ozone layer Biogeochemical Cycles Affect Global Climate Greenhouse Effect: Earth’s surface re-emits energy in longer, less energetic infrared wavelengths. Some of this infrared radiation is absorbed by gas molecules in the atmosphere (greenhouse gases). The molecules are warmed and radiate photons back to Earth’s surface, keeping the energy within the Earth system as heat. Biogeochemical Cycles Affect Global Climate Greenhouse gases include H2O, CO2, CH4, N2O. Without the atmosphere, Earth’s average surface temperature would be about 34°C colder than at present. Global Temperatures Are Increasing Ecological Challenges Can Be Addressed through Science and International Cooperation Governments have cooperated to support large-scale initiatives, such as the Intergovernmental Panel on Climate Change (IPCC). International agreements include: • Montreal Protocol to prevent depletion of UV-absorbing ozone • Kyoto Protocol to reduce emissions of greenhouse gases • Convention on International Trade in Endangered Species (CITES), to conserve species by eliminating international trade. What organism conducts nitrogen fixation? What compounds are necessary for cellular respiration to take place? Use these three ecology terms (community, ecosystem, population) to identify the following: 1) The mussels on the Main St. Pier in Huntington Beach. 2) The Santa Ana River. 3) All of the biota (living organisms) in Big Bear Lake. 1)What are the three steps in the nitrogen cycle? What organism performs the process? 2) Why is phosphorus necessary to living organisms? 3) Name one source of carbon in the atmosphere. 4) Water evaporates from the leaves of plants in a process called: