Ecosystems: Components, Energy Flow, and Matter Cycling “All things come from earth, and to earth they all return”—Menander

Ecology and the levels of organization of matter Ecology—Greek oikos meaning house Study of how organisms interact with one another and their non-living environment (biotic and abiotic components) Studies connections in nature on the thin life supporting membrane of air, water, and soil Levels of Organization of Matter Subatomic to biosphere

Ecosystem Organization Biosphere Ecosystems Communities Populations Organisms Organisms Made of cells Eukaryotic vs Prokaryotic Species Groups of organisms that resemble one another in appearance, behavior, and genetic make up Sexual vs Asexual reproduction Production of viable offspring in nature 1.5 million named; 10-14 million likely Populations Genetic diversity Communities Ecosystems Biosphere Fig. 4.2, p. 66

Earth’s Life Support Systems Troposphere To 11 miles Air is here Stratosphere 11 to 30 miles Ozone layer Hydrosphere Solid, liquid, and gaseous water Lithosphere Crust and upper mantle Contains non-renewable res. Atmosphere Vegetation and animals Soil Rock Biosphere Crust core Mantle Lithosphere (crust, top of upper mantle) Hydrosphere (water) (air) (Living and dead organisms) (soil and rock)

Sustaining Life on Earth… One way flow of high quality energy The cycling of matter (the earth is a closed system) Gravity Causes downward movement of matter Biosphere Carbon cycle Phosphorus Nitrogen Water Oxygen Heat in the environment Heat

Major Ecosystem Components Abiotic Components Water, air, temperature, soil, light levels, precipitation, salinity Sets tolerance limits for populations and communities Some are limiting factors that structure the abundance of populations Biotic Components Producers, consumers, decomposers Plants, animals, bacteria/fungi Biotic interactions with biotic components include predation, competition, symbiosis, parasitism, commensalism etc.

Limiting Factors on Land & in H2O Terrestrial Sunlight Temperature Precipitation Soil nutrients Fire frequency Wind Latitude Altitude Aquatic/Marine Light penetration Water clarity Water currents Dissolved nutrient concentrations Esp. N, P, Fe Dissolved Oxygen concentration Salinity

The Source of High Quality Energy Solar radiation Energy in = Energy out Reflected by atmosphere (34%) UV radiation Absorbed by ozone by the earth Visible light Lower Stratosphere (ozone layer) Troposphere Heat Greenhouse effect Radiated by atmosphere as heat (66%) Earth Heat radiated Energy of sun lights and warms the planet Supports PSN Powers the cycling of matter Drives climate and weather that distribute heat and H2O

Fate of Solar Energy… Earth gets 1/billionth of sun’s output of energy 34% is reflected away by atmosphere 66% is absorbed by chemicals in atmosphere = re-radiated into space Visible light, Infrared radiation (heat), and a small amount of UV not absorbed by ozone reaches the atmosphere Energy warms troposphere and land Evaporates water and cycles it along with gravity Generates winds A tiny fraction is captured by photosynthesizing organisms Natural greenhouse effect vs. Global Warming

Primary Productivity The conversion of light energy to chemical energy is called “gross primary production.” Plants use the energy captured in photosynthesis for maintenance and growth. The energy that is accumulated in plant biomass is called “net primary production.” Primary Production in Plants The total production of organic compounds by plants is referred to as primary productivity or production. This represents the total amount of light energy transformed into chemical energy through photosynthesis. Only about 1 – 5 % of the solar energy in any given location actually is captured for use or storage by plants. After the metabolic requirements of producers (plants or other photosynthetic organisms) are met, the total energy (accumulated as biomass) available to be passed through the food chain is called net primary productivity. References: Campbell, N.E., & Reece, J.B. (2002). Biology,(6th ed.). San Francisco: Benjamin Cummings. Raven, P.H., & Johnson, G.B. (2002). Biology, (6th ed.). McGraw-Hill. Image Reference: Baylor College of Medicine, Center For Educational Outreach. (2004). Martha Young, Senior Graphic Designer.

Primary Productivity NPP=GPP-respiration rate GPP= RATE at which producers convert solar energy into chemical energy as biomass Rate at which producers use photosynthesis to fix inorganic carbon into the organic carbon of their tissues These producers must use some of the total biomass they produce for their own respiration NPP= Rate at which energy for use by consumers is stored in new biomass (available to consumers) Units Kcal/m2/yr or g/m2/yr How do you measure it? AP Lab Site Most productive vs. least productive

What are the most productive Ecosystems? Estuaries Swamps and marshes Tropical rain forest Temperate forest Northern coniferous forest (taiga) Savanna Agricultural land Woodland and shrubland Temperate grassland Lakes and streams Continental shelf Open ocean Tundra (arctic and alpine) Desert scrub Extreme desert 800 1,600 2,400 3,200 4,000 4,800 5,600 6,400 7,200 8,000 8,800 9,600 Average net primary productivity (kcal/m2/yr)

Fate of Primary Productivity and Some important questions… Since producers are ultimate source of all food, why shouldn’t we just harvest the plants of the world’s marshes? Why don’t we clear cut tropical rainforests to grow crops for humans? Why not harvest primary producers of the world’s vast oceans? Vitousek et al: Humans now use, waste, or destroy about 27% of earth’s total potential NPP and 40% of the NPP of the planet’s terrestrial ecosystems

Biotic Components of Ecosystems Producers (autotrophs) Source of all food Photosynthesis Consumers=heterotroph Aerobic respiration Anaerobic respiration Methane, H2S Decomposers Matter recyclers… Release organic compounds into soil and water where they can be used by producers Heat Abiotic chemicals (carbon dioxide, oxygen, nitrogen, minerals) Producers (plants) Decomposers (bacteria, fungus) Consumers (herbivores, carnivores) Solar energy

Trophic Levels Each organism in an ecosystem is assigned to a feeding (or Trophic) level Primary Producers Primary Consumers (herbivores) Secondary Consumer (carnivores) Tertiary Consumers Omnivores Detritus feeders and scavengers Directly consume tiny fragments of dead stuff Decomposers Digest complex organic chemicals into inorganic nutrients that are used by producers Complete the cycle of matter

Detritivores vs Decomposers stop Fig. 4.15, p. 75 Mushroom Wood reduced to powder Long-horned beetle holes Bark beetle engraving Carpenter ant galleries Termite and carpenter work Dry rot fungus Detritus feeders Decomposers Time progression Powder broken down by decomposers into plant nutrients in soil

Energy Flow and Matter Cycling in Ecosystems… Food Chains vs. Food Webs KEY: There is little if no matter waste in natural ecosystems! Heat First Trophic Level Second Trophic Third Trophic Fourth Trophic Solar energy Producers (plants) Primary consumers (herbivores) Tertiary (top carnivores) Secondary (carnivores) Detritvores (decomposers and detritus feeders)

Generalized Food Web of the Antarctic Fig. 4.18, p. 77 Humans Blue whale Sperm whale Crabeater seal Killer whale Elephant seal Leopard Adélie penguins Petrel Fish Squid Carnivorous plankton Krill Phytoplankton Herbivorous zooplankton Emperor penguin Note: Arrows Go in direction Of energy flow…

Food Webs and the Laws of matter and energy Food chains/webs show how matter and energy move from one organism to another through an ecosystem Each trophic level contains a certain amount of biomass (dry weight of all organic matter) Chemical energy stored in biomass is transferred from one trophic level to the next With each trophic transfer, some usable energy is degraded and lost to the environment as low quality heat Thus, only a small portion of what is eaten and digested is actually converted into an organisms’ bodily material or biomass (WHAT LAW ACCOUNTS FOR THIS?)

Food Webs and the Laws of matter and energy Food chains/webs show how matter and energy move from one organism to another through an ecosystem Each trophic level contains a certain amount of biomass (dry weight of all organic matter) Chemical energy stored in biomass is transferred from one trophic level to the next With each trophic transfer, some usable energy is degraded and lost to the environment as low quality heat Thus, only a small portion of what is eaten and digested is actually converted into an organisms’ bodily material or biomass (WHAT LAW ACCOUNTS FOR THIS?) Ecological Efficiency: The % of usable nrg transferred as biomass from one trophic level to the next (ranges from 5-20% in most ecosystems, use 10% as a rule of thumb) Thus, the more trophic levels or steps in a food chain, the greater the cumulative loss of useable energy…

Food Webs and the Laws of matter and energy Ecological Efficiency: The % of usable energy transferred as biomass from one trophic level to the next (ranges from 5-20% in most ecosystems, use 10% as a rule of thumb) Thus, the more trophic levels or steps in a food chain, the greater the cumulative loss of useable energy…

Pyramids of Energy and Matter Pyramid of Energy Flow Pyramid of Biomass Heat 10 100 1,000 10,000 Usable energy Available at Each tropic level (in kilocalories) Producers (phytoplankton) Primary consumers (zooplankton) Secondary (perch) Tertiary (human) Decomposers

Ecological Pyramids of Energy Energy in ecosystems flows from producers (photosynthetic organisms) to consumers (herbivores and carnivores). Ecological pyramids of energy usually depict the amount of living material (or its energetic equivalent) that is present in different trophic levels. In this diagram, energy is depicted in kilocalories. Primary producers convert only about 1% of the energy in available sunlight. The average amount of energy that is available to the next trophic level is about 10%. Because so much energy is utilized in building and maintaining organisms, food chains (series of feeding relationships) are usually limited to just three or four steps. Pyramids of energy can not be inverted. References: Campbell, N.E., & Reece, J.B. (2002). Biology,(6th ed.). San Francisco: Benjamin Cummings. Holligan, P.M., Harris,R.P., Newell, R.C., Harbour, D.C., Head, R.N., Linley, E.A.S., Lucas, M.I., Tranter, P.R.G., Weekly, C.M. (1984). Vertical distribution and partitioning of organic carbon in mixed, frontal, and stratified waters of the English Channel. Marine Ecology Progress Series, 14, 111-127. Raven, P.H., & Johnson, G.B. (2002). Biology, (6th ed.). McGraw-Hill. Image Reference: Baylor College of Medicine, Center For Educational Outreach. (2004). Martha Young, Senior Graphic Designer.

Ecological Pyramids of Biomass The total dry weight of organisms (standing crop) in a particular trophic level is referenced as biomass. Most pyramids follow the typical pattern of narrowing at each level, however in some aquatic ecosystems, the pyramid may be inverted. In the example, phytoplankton grow and reproduce so rapidly that they can support a large population of zooplankton even though at any one time, the biomass of phytoplankton is smaller than that of the zooplankton. References: Campbell, N.E., & Reece, J.B. (2002). Biology,(6th ed.). San Francisco: Benjamin Cummings. Holligan, P.M., Harris,R.P., Newell, R.C., Harbour, D.C., Head, R.N., Linley, E.A.S., Lucas, M.I., Tranter, P.R.G., Weekly, C.M. (1984). Vertical distribution and partitioning of organic carbon in mixed, frontal, and stratified waters of the English Channel. Marine Ecology Progress Series, 14, 111-127. Raven, P.H., & Johnson, G.B. (2002). Biology, (6th ed.). McGraw-Hill. Image Reference: Baylor College of Medicine, Center For Educational Outreach. (2004). Martha Young, Senior Graphic Designer.

Implications of Pyramids…. Why could the earth support more people if the eat at lower trophic levels? Why are food chains and webs rarely more than four or five trophic levels? Why do marine food webs have greater ecological efficiency and therefore more trophic levels than terrestrial ones? Why are there so few top level carnivores? Why are these species usually the first to suffer when the the ecosystems that support them are disrupted?

Ecosystem Services and Sustainability Solar Capital Air resources and purification Climate control Recycling vital chemicals Renewable energy Nonrenewable mineral Potentially renewable matter Biodiversity and gene pool Natural pest and disease Waste removal and detoxification Soil formation renewal Water Lessons From Nature! Use Renewable Solar Energy As Energy Source Recycle the chemical nutrients needed for life

Matter Cycles You are responsible for knowing the water, carbon, nitrogen, sulfur, and phosphorus cycles Know major sources and sinks Know major flows Know how human activities are disrupting these cycles

Carbon Cycle Carbon Cycle Carbon, in the form of carbon dioxide, comprises about 0.03 percent of the atmosphere. Worldwide circulation of carbon atoms is called the carbon cycle. Since carbon becomes incorporated into molecules used by living organisms during photosynthesis, parts of the carbon cycle closely parallel the flow of energy through the earth’s living systems. Carbon is found in the atmosphere, the oceans, soil, fossil deposits and living organisms. Photosynthetic organisms create carbon-containing molecules (known as “organic” compounds), which are passed to other organisms as depicted in food webs. Each year, about 75 billion metric tons of carbon are trapped in carbon-containing compounds through photosynthesis. Carbon is returned to the environment through respiration (breakdown of sugar or other organic compounds), combustion (burning of organic materials, including fossil fuels), and erosion. References: Campbell, N.E., & Reece, J.B. (2002). Biology,(6th ed.). San Francisco: Benjamin Cummings. Image Reference: Baylor College of Medicine, Center For Educational Outreach. (2004). Martha Young, Senior Graphic Designer.

Nitrogen Cycle Nitrogen Cycle A major component of the atmosphere, nitrogen is essential for all living things. However, most organisms are unable to use the gaseous forms of nitrogen present in the atmosphere. In order for nitrogen to be usable by most organisms, it must be “fixed,” in other words, combined with oxygen, hydrogen or carbon to form other molecules. Nitrogen fixation can happen during rainstorms, which yields nitrate and ammonium ions. Nitrogen also can be fixed biologically by free-living and symbiotic bacteria. Leguminous plants, for example, host nitrogen-fixing bacteria in root nodules allowing them to capture nitrogen and incorporate it into proteins and other molecules. Unlike other organisms, nitrogen fixing bacteria are able to convert atmospheric nitrogen to ammonia, which then can serve as raw material for the incorporation of nitrogen into other molecules. The other four important steps in the nitrogen cycle are: (1) assimilation (reduction of nitrate ions [NO2-] inside plants to ammonium ions [NH4+], which are used to manufacture proteins and other molecules; this conversion requires energy); (2) ammonification (release of excess nitrogen in the form of ammonia [NH3] and ammonium ions [NH4+] by soil-dwelling bacteria and some fungi during the decomposition of complex organic compounds such as proteins, and nucleic acids); (3) nitrification (the oxidation of ammonium ions or ammonia by free-living, soil dwelling bacteria to nitrates [NO2-]; and (4) denitrification (the conversion of nitrate to gaseous nitrogen [N2 ] by free-living bacteria in soil; this conversion yields energy and occurs in conditions with low levels of oxygen). References: Campbell, N.E., & Reece, J.B. (2002). Biology,(6th ed.). San Francisco: Benjamin Cummings. Image Reference: Baylor College of Medicine, Center For Educational Outreach. (2004). Martha Young, Senior Graphic Designer.