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 Nutrient Cycling Producers Autotrophs (plants and other self-feeding organisms) Consumers Heterotrophs (animals, most fungi, many protists, many bacteria) Energy output (mainly metabolic heat)

The role of organisms in an ecosystem Simple Ecosystem Model

Consumers Herbivores Carnivores Parasites Omnivores Decomposers Detritivores SPRING rodents, rabbits fruits insects birds SUMMER rodents, rabbits fruits 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 5th 4th 3rd 2nd 1st Fourth-level consumers (heterotrophs): Top carnivores, parasites, detritivores, decomposers Third-level consumers (heterotrophs): Carnivores, parasites, detritivores, decomposers Second-level consumers (heterotrophs): Carnivores, parasites, detritivores, decomposers First-level consumers (heterotrophs): Herbivores, parasites, detritivores, decomposers Primary producers (autotrophs): 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

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 crow upland sandpiper garter snake frog spider weaselbadgercoyote ground squirrelpocket gopherprairie vole sparrow earthworms, insects First Trophic Level Second Trophic Level Higher Trophic Levels Connections in a tallgrass prairie food web grasses, composites Fig. 30-4, p.529

Rain-forest food web Rain Forest

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 5 decomposers, detritivores (bacteria, crayfish) third-level carnivores (gar, large-mouth bass) second-level consumers (fishes, invertebrates) first-level consumers (herbivorous fishes, turtles, invertebrates) primary producers (algae, eelgrass, rooted plants) 809

Energy Pyramid Primary producers trapped about 1.2% of the solar energy that entered the ecosystem 6–16% passed on to next level ,368 20,810 kilocalories/square meter/year top carnivores carnivores herbivores producers decomposers + detritivores = 5,080

Energy flow at Silver Springs Silver Springs Study

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 ocean land evaporation from ocean 425,000 precipitation into ocean 385,000 evaporation from land plants (evapotranspiration) 71,000 precipitation onto land 111,000 wind-driven water vapor 40,000 surface and groundwater flow 40,000

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

Threats to aquifers Aquifer Problems

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

Carbon dioxide and temperature Greenhouse Gases

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 phosphorus- poor 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