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Biology, 9th ed, Sylvia Mader
Chapter 48 Chapter 48 Ecosystems & Human Interferences Ecosystems & Human Interferences
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The Nature of Ecosystems
Outline The Nature of Ecosystems Biotic Components Autotrophs Heterotrophs Energy Flow Ecological Pyramids Global Biogeochemical Cycles Hydrologic Cycle Carbon Cycle Nitrogen Cycle Phosphorus Cycle
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Nature of Ecosystems Biosphere is the organism-containing part of the
Atmosphere Hydrosphere, and Lithosphere An ecosystem is a place where organisms interact with the physical environment Ecosystems characterized by: Cyclical flow of materials from abiotic environment through biotic community and back One-way flow of energy
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Ecosystems
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Biotic Components: Autotrophs
Producers are autotrophs Require only inorganic nutrients and an outside energy source to produce organic nutrients Photoautotrophs Chemoautrophs
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Biotic Components: Heterotrophs
Consumers are heterotrophs Require a source of preformed organic nutrients Herbivores - Feed on plants Carnivores - Feed on other animals Omnivores - Feed on plants and animals Decomposers are also heterotrophs Bacteria and fungi Break down dead organic matter
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Biotic Components
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Energy Flow and Chemical Cycling
Nutrients pass one-way through food chain from one level to another Each level retains some energy The rest is converted to heat, which dissipates into the environment Chemicals cycle as organic nutrients Once used, they are returned back to the producers by Excretion Death Cellular Respiration
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Nature of an Ecosystem
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Energy Balances
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Grazing & Detrital Food Webs
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Ecological Pyramids A trophic level
Composed of all the organisms that feed at the same level in a food chain Only about 10% of the energy of one trophic level is useable to the next trophic level Explains why few top carnivores can be supported in a food web
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Ecological Pyramid
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Global Biogeochemical Cycles
Chemical cycling may involve: Reservoir - Source normally unavailable to producers Fossil Fuels Minerals Sediments Exchange Pool - Source from which organisms generally take chemicals Atmosphere Soil Water Biotic Community - Chemicals remain in food chains, perhaps never entering a pool
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Model for Chemical Cycling
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Hydrologic Cycle Fresh water evaporates from bodies of water Precipitation on land enters the ground, surface waters, or aquifers Water eventually returns to the oceans
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The Hydrologic (Water) Cycle
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Atmosphere is an exchange pool for carbon dioxide
Carbon Cycle Atmosphere is an exchange pool for carbon dioxide The total amount of carbon dioxide in the atmosphere has been increasing every year Thought to be due to fossil fuel combustion Transfer Rate
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The Carbon Cycle
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Greenhouse Effect Greenhouse gases If Earth’s temperature rises
Carbon dioxide, nitrous oxide, methane Allow sunlight to pass through atmosphere Reflect infrared back to earth Trap heat in atmosphere If Earth’s temperature rises More water will evaporate More clouds will form, and Setting up a potential positive feedback loop
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Earth’s Radiation Balances
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Atmospheric nitrogen is fixed by bacteria
Nitrogen Cycle Atmospheric nitrogen is fixed by bacteria Make it available to plants Nodules on legume roots Nitrification - Production of nitrates Denitrification - Conversion of nitrate to nitrous oxide and nitrogen gas Balances nitrogen fixation
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The Nitrogen Cycle
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Nitrogen and Air Pollution
Acid Deposition Nitrogen oxides and sulfur dioxide are converted to acids when they combine with water vapor Acid rain dramatically reduces pH of surface waters in some areas Causes heavy metals to leach out of rocks, poisoning aquatic organisms Kills plants and causes fish to be unfit for human consumption Smog
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Acid Deposition
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Thermal Inversion
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Phosphorus does not enter the atmosphere
Phosphorus Cycle Phosphorus does not enter the atmosphere Sedimentary cycle Phosphate taken up by producers incorporated into a variety of organic molecules Can lead to water eutrophication Biomagnification
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The Phosphorus Cycle
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Sources of Water Pollution
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The Nature of Ecosystems
Review The Nature of Ecosystems Biotic Components Autotrophs Heterotrophs Energy Flow Ecological Pyramids Global Biogeochemical Cycles Hydrologic Cycle Carbon Cycle Nitrogen Cycle Phosphorus Cycle
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Biology, 9th ed, Sylvia Mader
Chapter 48 Ending Slide Chapter 48 Ecosystems & Human Interferences Ecosystems & Human Interferences
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