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Ecosystems Chapter 30 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 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 Tall-Grass Prairie Food Web marsh hawk sandpiper crow snake frog weasel badger coyote spider sparrow earthworms, insects vole pocket gopher grasses, composites ground squirrel 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 Which statement about ecosystems is false? 1. 2. 3. 4. energy flows in a cycle between producers and consumers nutrients are recycled by passing from producers to consumers and back again via decomposers in most ecosystems, energy flow begins with the capture of solar energy by photosynthesizers heterotrophs include bacteria and fungi 25% 1 25% 2 25% 3 25% 4 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 Grazing Food Web Detrital Food Web Two Types of Food Webs Energy Input: Energy Input: Transfers: Transfers: Producers (photosynthesizers) Producers (photosynthesizers) energy in organic wastes, remains herbivores carnivores energy losses as metabolic heat and as net export from ecosystem energy in organic wastes, remains detritivores detritivores decomposers Energy Output decomposers decomposers Energy Output energy losses as metabolic heat and as net export from ecosystem 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 Watershed • A region where precipitation is funneled into a single stream or river Hubbard Brook Experiment • A watershed was experimentally stripped of vegetation • All surface water draining from watershed was measured • Deforestation caused six-fold increase in calcium content of runoff water 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 Depletion Hawaiian Islands Alaska When the Earth's waters move from ocean to atmosphere to land and back again, it is called the _____ cycle. 25% 25% 25% 25% 1. water 2. hydrologic 3. hydrodynamic 4. precipitation 1 2 3 4 A watershed is _____. 1. a stream or river 2. a river that discharges water directly into the ocean 3. a region where precipitation becomes funneled into a single stream or river 4. a region where precipitation becomes funneled into a reservoir for use in human communities 25% 1 25% 2 25% 3 25% 4 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 diffusion between atmosphere and ocean bicarbonate and carbonate in ocean water photosynthesis combustion of fossil fuels aerobic respiration marine food webs death, incorporation sedimentation into sediments uplifting sedimentation marine sediments Carbon Cycle: Marine atmosphere combustion of fossil fuels volcanic action terrestrial rocks weathering photosynthesis aerobic combustion respiration of wood deforestation land food webs soil water leaching, runoff death, burial, compaction over geologic time Carbon Cycle: Land peat, fossil fuels My Carbon Cycle 1. I eat carbohydrate molecules. – These are molecules of fuel which I will “burn”. – Some of the energy released when I burn them will be trapped for me to use. The rest will be lost as heat. 2. The waste products of burned fuel are carbon dioxide and water. I breathe these out. 3. Plants (or other producers) take in carbon dioxide from the atmosphere and use it to make carbohydrate. According to the last slide, why do I eat carbohydrates? .. lo w ... ai n th e y ar e co nt y B ec au se th e B ec au se au se ec B ec au se th e th e y y ta s co nt te ai n ... ... 25% 25% 25% 25% B 1. Because they taste good. 2. Because they contain lots of vitamins. 3. Because they contain lots of energy. 4. Because they are low in calories. Energy saved from burning up my fuel is saved in the form of : 25% H ea t t 25% Fa 25% TP us cl e 25% A Muscle ATP Fat Heat M 1. 2. 3. 4. The only reason I need to breathe in oxygen is : iv e rr os ... = n co rb o is ge n xy O xy O iv i ll l A ge n ng + th ca in gs to yg en ox d ee ne e. “b u. .. .. . 25% 25% 25% 25% In 1. I need oxygen to “burn” fuel molecules. 2. All living things need oxygen. 3. Oxygen + carbon = carbon dioxide. 4. Oxygen is corrosive. Breathing out : th e of r id et s G ... w as t ca lo tra ex ur ns B e e. .. s ce s ex of r id et s G fu m ... ul at e re g e m el ps rie s . 25% 25% 25% 25% H 1. Helps me regulate my body temperature. 2. Gets rid of excess fuel molecules. 3. Burns extra calories. 4. Gets rid of the waste products of burned fuel. The carbon in the plants I eat comes from : The atmosphere. The food they eat. The soil. Water. fo od e Th r. at e so e Th W . th ey ea t re . he os p at m e il. 25% 25% 25% 25% Th 1. 2. 3. 4. The carbon in the steak I eat comes from : 1. Supplements in animal feed. 2. Vitamins. 3. The cow’s drinking water. 4. The plants eaten by the cow. Th n ts e pl an w ’s ea te dr in ki ng by w ... t.. . ta m in s Vi co e Th Su pp le m en ts in an im a. .. 25% 25% 25% 25% Greenhouse Effect • Greenhouse gases impede escape of heat from Earth’s surface Global Warming Long-term increase in temperature of Earth’s lower atmosphere 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 Increasing 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 Fig. 30-16, p.538 Nitrogen Fixation • Plants cannot use nitrogen gas • Nitrogen-fixing bacteria convert nitrogen gas into ammonia (NH3) • Ammonia and ammonium can be taken up by plants Air Pollution • Effects of nitrogen oxides released by burning fossil fuels