The Nature of Ecosystems

1. Ecosystem An array of organisms and a physical environment, all interacting through a one-way flow of energy and a cycling of nutrients Sustained by ongoing inputs of energy and nutrients (open system) The Nature of Ecosystems

2. Primary producers (autotrophs) Obtain energy from nonliving sources (sunlight) Build organic compounds from CO2 and water Consumers (heterotrophs) Get energy and carbon from organic sources Carnivores, herbivores, parasites, omnivores Detritivores, such as earthworms and crabs, eat small particles of organic matter (detritus) Decomposers, such as bacteria and fungi, feed on organic wastes and remains and break them down into inorganic building blocks Overview of Participants

3. Energy flows one way Producers capture light energy and convert it to bond energy in organic molecules (photosynthesis) Metabolic reactions break bonds (aerobic respiration) and give off heat, which is not recycled Nutrients are cycled Producers take up inorganic compounds from the environment; decomposers return them Energy and Nutrients

4. energy input, mainly from sunlight A Energy from the environment flows through producers, then consumers. All energy that entered this ecosystem eventually flows out of it, mainly as heat. PRODUCERS plants and other self-feeding organisms nutrient cycling B Producers and consumers concentrate nutrients in their tissues. Some nutrients released by decomposition get cycled back to producers. CONSUMERS animals, most fungi, many protists, bacteria energy output, mainly heat.

5. ENERGY INPUT: ENERGY INPUT: ENERGY TRANSFERS: ENERGY TRANSFERS: Producers (photosynthesizers) Producers (photosynthesizers) energy lost at each conversion step from one trophic level to the next energy lost at each conversion step from one trophic level to the next energy in organic wastes, remains energy losses as metabolic heat and as net export from ecosystem energy in organic wastes, remains energy losses as metabolic heat and as net export from ecosystem decomposers herbivores carnivores detritivores energy inputs, outputs also occur between the two food webs decomposers ENERGY OUTPUT ENERGY OUTPUT

6. Fourth-level consumers (heterotrophs): Top carnivores, parasites, detritivores, decomposers 5th Third-level consumers (heterotrophs): 4th Carnivores, parasites, detritivores, decomposers Second-level consumers (heterotrophs): 3d Carnivores, parasites, detritivores, decomposers First-level consumers (heterotrophs): 2nd Herbivores, parasites, detritivores, decomposers Primary producers (autotrophs): 1st Photoautotrophs, chemoautotrophs

7. MARSH HAWK CROW HIGHER TROPHIC LEVELS Complex array of carnivores, omnivores and other consumers. Many feed at more than one trophic level continually, seasonally, or when an oppportunity presents itself UPLAND SANDPIPER GARTER SNAKE FROG WEASEL BADGER COYOTE SPIDER SECOND TROPHIC LEVEL Primary consumers (e.g., herbivores) CLAY-COLORED SPARROW EARTHWORMS, INSECTS (E.G., GRASSHOPPPERS, CUTWORMS) PRAIRIE VOLE POCKET GOPHER GROUND SQUIRREL FIRST TROPHIC LEVEL Primary producers

8. A biomass pyramid depicts dry weight of organisms at each trophic level in an ecosystem Largest tier is usually producers For some aquatic systems, pyramid is inverted An energy pyramid depicts the energy that enters each trophic level in an ecosystem Largest tier is always producers Ecological Pyramids

9. top carnivores 21 detritivores + decomposers = 5,060 carnivores 383 herbivores 3,368 producers 20,810

10. Energy Input 1,700,000 kcal per square meter per year Energy flow through living components 1,679,190 (98.8%) B Every year 1,700,000 kcal of solar energy fall on each square meter of the Silver Springs ecosystem. 20,810 (1.2%) producers Energy lost as heat or to flow downstream Energy in wastes, remains C 98.8 percent of this incoming energy is not captured by producers. Energy flow to the next trophic level 4,245 D Producers harness 20,810 kcal of energy, but transfer only 3,368 kcal to herbivores. The rest is lost as heat or ends up in wastes and remains. 3,368 13,197 herbivores 2,265 720 383 carnivores E With each subsequent transfer, only a small fraction of the energy reaches the next trophic level. 21 90 272 top carnivores Energy output 20,810 + 1,679,190 5 16 detritivores and decomposers Total annual energy flow 5,060 1,700,000 (100%)

11. In a biogeochemical cycle, an essential element moves from nonliving environmental reservoirs, into living organisms, then back to the reservoirs Elements essential to life (nutrients) include oxygen, hydrogen, carbon, nitrogen, phosphorus Biogeochemical Cycles

12. biogeochemical cycle Main nutrient reservoirs in the environment fraction of nutrient available to ecosystem herbivores, carnivores, parasites primary producers detritivores, decomposers

13. Main Reservoirs Volume (103 cubic kiometers) Oceans Polar ice, glaciers Groundwater Lakes, rivers Soil moisture Atmosphere (water vapor) 1,370,00029,000 4,000 230 67 14 ATMOSPERE precipitation onto land 111,000 wind driven water vapor 40,000 evaporation from land plants (evapotranspiration) 71,000 evaporation from ocean 425,000 precipitation into ocean 385,000 surface and groudwater flow 40,000 LAND OCEAN

14. Gaseous nitrogen (N2) makes up about 80 percent of the lower atmosphere; most organisms can’t use gaseous nitrogen. The nitrogen cycle starts with nitrogen fixation; nitrogen-fixing bacteria convert N2 in the air to their own organic nitrogen compounds. Next, other bacteria carry out ammonification, converting organic nitrogen to ammonia (NH3). Then, still other bacteria carry out nitrification, converting ammonia to nitrite (NO2-) and on to nitrate (NO3-). Finally, plants assimilate the nitrate into their organic compounds, closing the cycle. Nitrogen Cycle

15. GASEOUS NITROGEN (N2) IN ATMOSPHERE NITROGEN FIXATION by industry for agriculture FOOD WEBS ON LAND uptake by autotrophs excretion, death, decomposition uptake by autotrophs FERTILIZERS NO3- IN SOIL NITROGEN FIXATION bacteria convert to ammonia (NH3+) ; this dissolves to form ammonium (NH4+) NITROGENOUS WASTES, REMAINS IN SOIL DENTRIFICATION by bacteria 2. NITRIFICATION bacteria convert NO2-tonitrate (NO3-) AMMONIFICATION bacteria, fungi convert the residues to NH3; this dissolves to form NH4+ NH3-,NH4+ IN SOIL 1. NITRIFICATION bacteria convert NH4+ tonitrite (NO2-) NO2- IN SOIL loss by leaching loss by leaching

16. Denitrification Denitrifying bacteria convert nitrate or nitrite to gaseous nitrogen (N2) or nitrogen oxide (NO2) Human activity also removes nitrogen from the cycle via incineration (fuels and organic waste), creating a variety of air pollutants. Ammonium, nitrite, and nitrate are also lost from land ecosystems in runoff and by leaching Losing Nitrogen from Ecosystems

17. Biological magnification Some harmful substances, such as DDT, become increasingly concentrated in tissues of organisms as they move up the food chain Biological Magnification

18. 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 (compsite of several samples) Green alga (Cladophora grcilis) Plankton (mostlky zooplankton) Water 75.5 18.5 13.8 3.57 2.07 1.28 0.94 0.42 0.33 0.30 0.26 0.160.083 0.040 0.00005