Ecology II: Ecosystems Trophic Levels, Chains, Webs, Pyramids, Primary Productivity, Nutrient Cycles

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 Herbivores Carnivores Carnivores Parasites Parasites Omnivores Omnivores Decomposers Decomposers Detritivores 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 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

Food Web

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) herbivores carnivores decomposers detritivores ENERGY OUTPUT Grazing Food WebDetrital Food Web

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 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 the United States since the 1970s Birds that were top carnivores accumulated DDT in their tissues

FUMIGATION of workers using DDT

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

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

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) 809 primary producers (algae, eelgrass, rooted plants) Biomass pyramid

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 detritivores ,368 20,810 kilocalories/square meter/year top carnivores carnivores herbivores producers decomposers

Biogeochemical Cycle The flow of a nutrient from the environment to living organisms and back to the environment The flow of a nutrient from the environment to living organisms and back to the environment

Three Categories Hydrologic cycle Hydrologic cycle WaterWater Atmospheric cycles Atmospheric cycles Nitrogen and carbonNitrogen and carbon Sedimentary cycles Sedimentary cycles Phosphorus and sulfurPhosphorus and sulfur

Hydrologic Cycle evaporation from ocean 425,000 precipitation into ocean 385,000 evaporation from land plants (evapotranspiratio n) 71,000 precipitation onto land 111,000 wind driven water vapor 40,000 surface and groundwater flow 40,000 Atmosphere OceansLand

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 & nitrate content of the runoff water

Hubbard Brook Experiment A classic study of deforestation effects losses from disturbed watershed time of deforestation losses from undisturbed watershed

Nitrogen Cycle NO 3 - IN SOIL NITROGEN FIXATION by industry for agriculture FERTILIZERS FOOD WEBS ON LAND NH 3 -, NH 4 + IN SOIL 1. NITRIFICATION loss by leaching uptake by autotrophs excretion, death, decomposition uptake by autotrophs NITROGEN FIXATION loss by leaching AMMONIFICATION 2. NITRIFICATION NITROGENOUS WASTES, REMAINS IN SOIL GASEOUS NITROGEN (N 2 ) IN ATMOSPHERE NO 2 - IN SOIL

Carbon Cycle photosynthesis TERRESTRIAL ROCKS volcanic action weathering diffusion Bicarbonate, carbonate Marine food webs Marine Sediments Atmosphere Terrestrial Rocks Soil Water Peat, Fossil Fuels Land Food Webs

Carbon (Carbon Dioxide) in Atmosphere Carbon dioxide is added to atmosphere Carbon dioxide is added to atmosphere Aerobic respiration, volcanic action, burning fossil fuels Aerobic respiration, volcanic action, burning fossil fuels Removed by photosynthesis Removed by photosynthesis

Greenhouse Effect Greenhouse gases impede the escape of heat from Earth’s surface

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

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

Other Greenhouse Gases CFCs - synthetic gases used in plastics and in refrigeration CFCs - synthetic gases used in plastics and in refrigeration Methane - produced by termites and bacteria Methane - produced by termites and bacteria Nitrous oxide - released by bacteria, fertilizers, and animal wastes Nitrous oxide - released by bacteria, fertilizers, and animal wastes