KWL---FOOD CHAINS WHAT DO I KNOW ABOUT FOOD CHAINS WHAT DO I WANT TO KNOW ABOUT FOOD CHAINS ***WHAT HAVE I LEARNED ABOUT FOOD CHAINS

CHAPTER 47 ECOSYSTEMS

Impacts, Issues: Bye-Bye, Blue Bayou  Global warming presents many risks:  algal blooms and huge fish kills  intense heat waves and wildfires  less fresh drinking water  Knowledge of global energy flows and nutrients is required to address global warming

Fig. 47-1, p.842

p.843

Ecosystem An association of organisms and their physical environment, interconnected by ongoing flow of energy and a cycling of materials

Modes of Nutrition  Autotrophs  Capture sunlight or chemical energy  Producers  Heterotrophs  Extract energy from other organisms or organic wastes  Consumers, decomposers, detritivores

Simple Ecosystem Model energy input from sun nutrient cycling PHOTOAUTOTROPHS (plants, other producers) HETEROTROPHS (consumers, decomposers) energy output (mainly heat)

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  All the organisms at a trophic level are the same number of steps away from the energy input into the system  Producers are closest to the energy input and are the first trophic level

Trophic Levels in Prairie 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

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 garter snake cutworm flowering plants Fig. 47-4, p.845

Tall-Grass Prairie Food Web earthworms, insects sparrow vole pocket gopher ground squirrel coyote badgerweasel spider frog snake sandpipercrow marsh hawk grasses, composites

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 Sampling of connections in a tallgrass prairie food web grasses, composites Fig. 47-5, p.846

Energy Losses  Energy transfers are never 100 percent efficient  Some energy is lost at each step  Limits the number of trophic levels in an ecosystem

Two Types of Food Webs Producers (photosynthesizers) Energy Input: herbivores carnivores decomposers detritivores energy in organic wastes, remains Energy Output energy losses as metabolic heat & as net export from ecosystem Producers (photosynthesizers) decomposers detritivores Transfers: Grazing Food Web Detrital Food Web energy in organic wastes, remains energy losses as metabolic heat & as net export from ecosystem Figure 47.6 Page 847

Biological Magnification A nondegradable or slowly degradable substance becomes more and more concentrated in the tissues of organisms at higher trophic levels of a food web

DDT in Food Webs  Synthetic pesticide banned in United States since the 1970s  Birds that are carnivores accumulate DDT in their tissues, produce brittle egg shells

Fig. 47-7, p.848 Pesticides

Primary Productivity  Gross primary productivity is ecosystem’s total rate of photosynthesis  Net primary productivity is rate at which producers store energy in tissues in excess of their aerobic respiration

Primary Productivity Varies  Seasonal variation  Variation by habitat  The harsher the environment, the slower plant growth, the lower the primary productivity

Fig , p.850

Silver Springs Study  Aquatic ecosystem in Florida  Site of a 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

Pyramid of Energy Flow  Primary producers trapped about 1.2 percent 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 Figure Page 851

All Heat in the End  At each trophic level, the bulk of the energy received from the previous level is used in metabolism  This energy is released as heat energy and lost to the ecosystem  Eventually all energy is released as heat

Biogeochemical Cycle  The flow of a nutrient from the environment to living organisms and back to the environment  Main reservoir for the nutrient is in the environment

Three Categories  Hydrologic cycle  Water  Atmospheric cycles  Nitrogen and carbon and oxygen  Sedimentary cycles  Phosphorus and sulfur

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 Figure Page 853

Hubbard Brook Experiment  A watershed was experimentally stripped of vegetation  All surface water draining from watershed was measured  Removal of vegetation caused a six-fold increase in the calcium content of the runoff water

Hubbard Brook Experiment losses from disturbed watershed time of deforestation losses from undisturbed watershed Figure Page 854

Water Use and Scarcity  Most of Earth’s water is too salty for human consumption  Desalinization is expensive and requires large energy inputs  Irrigation of crops is the main use of freshwater

Negative Effects of Irrigation  Salinization, mineral buildup in soil  Elevation of the water table and waterlogging  Depletion of aquifers

Carbon Cycle  Carbon moves through the atmosphere and food webs on its way to and from the ocean, sediments, and rocks  Sediments and rocks are the main reservoir

Carbon in the Oceans  Most carbon in the ocean is dissolved carbonate and bicarbonate  Ocean currents carry dissolved carbon

Carbon in Atmosphere  Atmospheric carbon is mainly carbon dioxide  Carbon dioxide is added to atmosphere  Aerobic respiration, volcanic action, burning fossil fuels  Removed by photosynthesis

Greenhouse Effect  Greenhouse gases impede the escape of heat from Earth’s surface Figure 47-22, Page 858

Global Warming Long-term increase in the temperature of Earth’s lower atmosphere

Carbon Dioxide Increase  Carbon dioxide levels fluctuate seasonally  The 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 - produced by termites and bacteria  Nitrous oxide - released by bacteria, fertilizers, and animal wastes

Nitrogen Cycle  Nitrogen is used in amino acids and nucleic acids  Main reservoir is nitrogen gas in the atmosphere

Nitrogen Cycle gaseous nitrogen (N 2 ) in atmosphere NO 3 - in soil nitrogen fixation by industry fertilizers NH 3 -,NH 4 + in soil 1. Nitrification leaching uptake by autotrophs excretion, death, decomposition uptake by autotrophs nitrogen fixation leaching ammonification2. Nitrification dentrification nitrogenous wastes, remains NO 2 - in soil food webs on land Figure Page 860

Nitrogen Fixation  Plants cannot use nitrogen gas  Nitrogen-fixing bacteria convert nitrogen gas into ammonia (NH 3 )  Ammonia and ammonium can be taken up by plants

Ammonification & Nitrification  Bacteria and fungi carry out ammonification  conversion of nitrogenous wastes to ammonia  Nitrifying bacteria convert ammonium to nitrites and nitrates

Nitrogen Loss  Nitrogen is often a limiting factor in ecosystems  Nitrogen is lost from soils via leaching and runoff  Denitrifying bacteria convert nitrates and nitrites to nitrogen gas

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

Phosphorus Cycle  Phosphorus is part of phospholipids and all nucleotides  It is the most prevalent limiting factor in ecosystems  Main reservoir is Earth’s crust; no gaseous phase

Human Effects  In tropical countries, clearing lands for agriculture may deplete phosphorus-poor soils  In developed countries, phosphorus runoff is causing eutrophication of waterways

Fig , p.863 Eutrophication Experiments