Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Ecosystems Chapter 30 Bye-Bye Bayou • Louisiana’s coastal wetlands are disappearing • Global warming contributes to wetland’s demise • Sea levels rising worldwide • Burning fossil fuels raises global temperature Impacts, Issues Video Bye-Bye, Blue Bayou Ecosystem An array of organisms and their physical environment, interconnected through a one-way flow of energy and cycling of raw materials Modes of Nutrition • Photoautotrophs – Capture sunlight or chemical energy – Primary producers • Heterotrophs – Extract energy from other organisms or organic wastes – Consumers, decomposers, detritivores Simple Ecosystem Model Energy input from sun Producers Autotrophs (plants and other self-feeding organisms) Nutrient Cycling Consumers Heterotrophs (animals, most fungi, many protists, many bacteria) Energy output (mainly metabolic heat) Simple Ecosystem Model The role of organisms in an ecosystem Consumers • Herbivores • Carnivores • Parasites SPRING fruits insects rodents, rabbits birds • Omnivores • Decomposers • Detritivores SUMMER fruits rodents, rabbits insects birds seasonal variation in the diet of an omnivore (red fox) Trophic Levels • Feeding relationships – All organisms at a trophic level are the same number of steps away from the energy input into the system • Autotrophs are producers – closest to energy input – first trophic level Trophic Levels Fourth-level consumers (heterotrophs): 5th Top carnivores, parasites, detritivores, decomposers 4th Third-level consumers (heterotrophs): Carnivores, parasites, detritivores, decomposers Second-level consumers (heterotrophs): 3rd Carnivores, parasites, detritivores, decomposers First-level consumers (heterotrophs): 2nd Herbivores, parasites, detritivores, decomposers Primary producers (autotrophs): 1st Photoautotrophs, chemoautotrophs marsh hawk crow garter snake cutworm flowering plants fifth trophic level top carnivore (fourth-level consumer) fourth trophic level carnivore (third-level consumer) third trophic level carnivore (second-level consumer) second trophic level herbivore (primary consumer) first trophic level autotroph (primary producer) Fig. 30-3, p.528 Food Chain Food chain Food Chain • A straight-line sequence of who eats whom • Simple food chains are rare in nature marsh hawk upland sandpiper garter snake cutworm plants marsh hawk Higher Trophic Levels Connections in a tallgrass prairie food web crow upland sandpiper garter snake frog weasel spider Second Trophic Level sparrow earthworms, insects First Trophic Level badger coyote prairie vole pocket gopher ground squirrel grasses, composites Fig. 30-4, p.529 Rain Forest Rain-forest food web Energy Losses • Energy transfers are never 100% efficient • Some energy is lost at each step • Limits number of trophic levels in an ecosystem Biological Magnification Nondegradable or slowly degradable substances become more and more concentrated in tissues of organisms at higher trophic levels of a food web DDT in Food Webs • Synthetic pesticide banned in United States since 1970s • Carnivorous birds accumulate DDT in their tissues, produce brittle egg shells Fig. 30-5, p.530 Ecological Pyramids • Primary producers are bases for successive tiers of consumers • Biomass pyramid – Dry weight of all organisms • Energy pyramid – Usable energy decreases as it is transferred through ecosystem Biomass Pyramid • Aquatic ecosystem, Silver Springs, Florida • Long-term study of a grazing food web decomposers, detritivores (bacteria, crayfish) 5 1.5 third-level carnivores (gar, large-mouth bass) 1.1 second-level consumers (fishes, invertebrates) 37 first-level consumers (herbivorous fishes, turtles, invertebrates) 809 primary producers (algae, eelgrass, rooted plants) Energy Pyramid • Primary producers trapped about 1.2% of the solar energy that entered the ecosystem • 6–16% passed on to next level 21 top carnivores decomposers + detritivores = 5,080 carnivores herbivores 383 3,368 producers 20,810 kilocalories/square meter/year Silver Springs Study Energy flow at Silver Springs Biogeochemical Cycle • Flow of an essential substance from the environment to living organisms and back to the environment • Main reservoir is in the environment • Geologic processes, decomposers aid cycles Three Categories • Hydrologic cycle – Water • Atmospheric cycles – Nitrogen and carbon • Sedimentary cycles – Phosphorus and other nutrients Hydrologic Cycle atmosphere wind-driven water vapor 40,000 evaporation precipitation from ocean into ocean 425,000 385,000 precipitation onto land 111,000 evaporation from land plants (evapotranspiration) 71,000 surface and groundwater flow 40,000 ocean land Hydrologic Cycle Hydrologic cycle Global Water Crisis • Limited amount of fresh water • Desalinization is expensive and requires large amounts of energy • Aquifers are being depleted • Groundwater is contaminated • Sewage, agricultural runoff, and industrial chemicals pollute rivers Aquifer Problems Threats to aquifers Carbon Cycle • Carbon moves through atmosphere, food webs, ocean, sediments, and rocks • Sediments and rocks are the main reservoir • Combustion of fossil fuels changes natural balance Carbon Cycle Carbon cycle Greenhouse Effect • Greenhouse gases impede escape of heat from Earth’s surface Greenhouse Effect Greenhouse effect Global Warming Long-term increase in temperature of Earth’s lower atmosphere Greenhouse Gases Carbon dioxide and temperature Carbon Dioxide Increase • Carbon dioxide levels fluctuate seasonally • Average level is steadily increasing • Burning of fossil fuels and deforestation are contributing to the increase Other Greenhouse Gases • CFCs: synthetic gases used in plastics and in refrigeration • Methane: released by natural gas production, livestock • Nitrous oxide: released by bacteria, fertilizers, and animal wastes Greenhouse Gases Greenhouse gases Table 30-1, p.537 Nitrogen Cycle • Nitrogen is used in amino acids and nucleic acids • Main reservoir is nitrogen gas in the atmosphere • Nitrogen gas can’t enter food web Nitrogen Cycle Nitrogen cycle Human Effects • Humans increase rate of nitrogen loss by clearing forests and grasslands • Humans increase nitrogen in water and air by using fertilizers and by burning fossil fuels • Too much or too little nitrogen can compromise plant health Air Pollution • Effects of nitrogen oxides released by burning fossil fuels Deforestation Effect of air pollution in forests Phosphorus Cycle • Phosphorus is part of phospholipids, nucleotides, NADH, ATP • Main limiting factor in ecosystems • Reservoir is Earth’s crust; no gaseous phase Phosphorus Cycle Phosphorus cycle Human Effects • In tropical countries, clearing lands for agriculture may deplete phosphoruspoor soils • In developed countries, fertilizer causes phosphorus overloads in soil Eutrophication • Phosphorus is limiting factor in many freshwater ecosystems • Runoff from phosphate fertilizers accelerates algal growth in waterways • Resulting dense algal blooms cause system overload and death Clouds Move Stream