Chapter 47 Ecosystem Fig 47 1 p 842

Chapter 47: Ecosystem

Fig. 47 -1, p. 842

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 PHOTOAUTOTROPHS (plants, other producers) nutrient cycling HETEROTROPHS (consumers, decomposers) energy output (mainly heat)

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

Food Chain marsh hawk • A straight-line sequence upland sandpiper of who eats whom • Simple food chains are garter snake rare in nature cutworm plants

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

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 Sampling of 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. 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

Energy Input: Grazing Food Web Detrital Food Web Energy Input: Two Types of Food Webs Transfers: Producers (photosynthesizers) energy in organic wastes, remains herbivores carnivores decomposers Energy Output energy losses as metabolic heat & as net export from ecosystem energy in organic wastes, remains decomposers Energy Output detritivores 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 1970 s • Almost caused Bald Eagles to go Extinct • Birds that are carnivores accumulate DDT in their tissues, produce brittle egg shells

DDT in an Estuary (1967) DDT Residues (ppm wet weight of whole live organism) Ring-billed gull fledgling (Larus delawarensis) Herring gull (Larus argentatus) Osprey (Pandion haliaetus) Green heron (Butorides virescens) Atlantic needlefish (Strongylira marina) Summer flounder (Paralychthys dentatus) Sheepshead minnow (Cyprinodon variegatus) Hard clam (Mercenaria mercenaria) Marsh grass shoots (Spartina patens) Flying insects (mostly flies) Mud snail (Nassarius obsoletus) Shrimps (composite of several samples) Green alga (Cladophora gracilis) Plankton (mostly zooplankton) Water 75. 5 18. 5 13. 8 3. 57 2. 07 1. 28 0. 94 0. 42 0. 33 0. 30 0. 26 0. 16 0. 083 0. 040 0. 00005

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. 47 -10, p. 850

Fig. 47 -10 a, p. 850

north polar tropical Photosynthetic biomass north temperate JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC JAN Fig. 47 -10 b, p. 850

Silver Springs Study • Aquatic ecosystem in Florida • Site of a 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)

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 21 top carnivores herbivores producers decomposers + detritivores = 5, 080 383 3, 368 20, 810 kilocalories/square meter/year Figure 47. 13 Page 851

Incoming solar Energy Flow In energy not 1, 700, 000 kilocalories harnessed: Silver Springs 1, 679, 190 (98. 8%) ENERGY INPUT: Energy in organic wastes and remains: 4, 245 20, 810 (1. 2%) Energy losses as metabolic heat & as net export Producers from To next trophic level: ecosystem: 3, 368 Herbivores 720 383 Carnivores 90 21 Top carnivores 5 Figure 47 -13 Page 851 13, 197 2, 265 272 16 Decomposers, detritivores 5, 060 ENERGY OUTPUT: 20, 810 1, 679, 190 Total annual energy flow: 1, 700, 000 (100%)

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

Main nutrient reservoirs in the environment fraction of nutrient available to ecosystem geochemical cycle primary producers herbivores, carnivores, parasites detritivores, decomposers Fig. 47 -14, p. 852

Three Categories • Hydrologic cycle – Water • Atmospheric cycles – Nitrogen and carbon • Sedimentary cycles – Phosphorus and sulfur

Hydrologic Cycle

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

Fig. 47 -18, p. 855

Aquifer Problems Figure 47 -19 Page 855

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

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 Figure 47 -20 Page 856

atmosphere combustion of fossil fuels volcanic action terrestrial rocks weathering photosynthesis aerobic combustion respiration of wood land food webs sedimentation soil water leaching, runoff death, burial, compaction over geologic time Carbon Cycle - Land peat, fossil fuels Figure 47 -20 Page 856

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

Fig. 47 -23 a, p. 859

Fig. 47 -23 b, p. 859

Fig. 47 -23 c, p. 859

Fig. 47 -23 d, p. 859

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

Fig. 47 -24, p. 860

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 Nitrogen cycle

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

mining fertilizer guano excretion uptake by autotrophs uptake by weathering producers marine food webs dissolved in seawater leaching, runoff death, decomposition sedimentation land food webs death, decomposition settling out marine sediments dissolved in soil water, lakes, rivers agriculture weathering uplifting over geologic time terrestrial rocks Phosphorus cycle Fig. 47 -27, p. 862

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

Phosphorus Cycle Phosphorus cycle

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

Eutrophication Experiments Fig. 47 -28, p. 863