Energy Flow in Ecosystems and Biogeochemical Cycles

Hierarchy of ecology Individual Individual Population Population Community Community Ecosystem Ecosystem Biosphere Biosphere

What’s an Ecosystem? An ecosystem consists of all the organisms (biotic) in a community and the environment (abiotic) with which they interact. An ecosystem consists of all the organisms (biotic) in a community and the environment (abiotic) with which they interact. Ecosystems can be as small as the microorganisms living on your skin or as large as the entire biosphere. Ecosystems can be as small as the microorganisms living on your skin or as large as the entire biosphere.

Producer Herbivore (primary consumer) Detritivores (decomposers) Carnivore (secondary consumer) Energy flow Energy flows THROUGH ecosystems – open system Chemical cycling Nutrients cycle WITHIN ecosystems – closed system

Energy Flow in Ecosystems Almost all energy used in ecosystems comes from the sun Almost all energy used in ecosystems comes from the sun From there it flows through a food chain or web and exits the ecosystem in the form of heat, light, kenetic or chemical energy From there it flows through a food chain or web and exits the ecosystem in the form of heat, light, kenetic or chemical energy

Energy pyramids show the efficiency of energy transfer between trophic levels Energy pyramids show the efficiency of energy transfer between trophic levels Generally 10% of energy is transferred Generally 10% of energy is transferred Food chains never get beyond 4-5 trophic levels Food chains never get beyond 4-5 trophic levels

Biogeochemical Cycling of Nutrients We have a finite supply of chemical elements We have a finite supply of chemical elements Abiotic reservoir – atmosphere, rocks Abiotic reservoir – atmosphere, rocks Biotic reservoir – within organisms Biotic reservoir – within organisms Biological processing – nitrogen fixation by bacteria, carbon fixation by photosynthesis Biological processing – nitrogen fixation by bacteria, carbon fixation by photosynthesis Which nutrients/molecules are important?

Atoms and Electron Shells

Biogeochemical Cycling of Nutrients We have a finite supply of chemical elements We have a finite supply of chemical elements Abiotic reservoir – atmosphere, rocks Abiotic reservoir – atmosphere, rocks Biotic reservoir – within organisms Biotic reservoir – within organisms Biological processing – nitrogen fixation by bacteria, carbon fixation by photosynthesis Biological processing – nitrogen fixation by bacteria, carbon fixation by photosynthesis Water cycle Water cycle Carbon cycle Carbon cycle Nitrogen cycle Nitrogen cycle Phosphorous cycle Phosphorous cycle } Local OR Global

LE Consumers Producers Nutrients available to producers Detritivores Biogeochemical Cycle Abiotic reservoir

Biogeochemical Cycling of Nutrients We have a finite supply of chemical elements We have a finite supply of chemical elements Abiotic reservoir – atmosphere, rocks Abiotic reservoir – atmosphere, rocks Biotic reservoir – within organisms Biotic reservoir – within organisms Biological processing – nitrogen fixation by bacteria, carbon fixation by photosynthesis Biological processing – nitrogen fixation by bacteria, carbon fixation by photosynthesis Water cycle Water cycle Carbon cycle Carbon cycle Nitrogen cycle Nitrogen cycle Phosphorous cycle Phosphorous cycle } Local OR Global Look on page 1232 and learn the cycles

What’s so great about water? Polar molecule Polar molecule High heat capacity – doesn’t change temperature rapidly High heat capacity – doesn’t change temperature rapidly Evaporative cooling Evaporative cooling Cohesion and adhesion Cohesion and adhesion “Universal” solvent “Universal” solvent Lower density when solid – ice floats Lower density when solid – ice floats Organisms are made of water Organisms are made of water

Water Cycle Solar energy drives the global water cycle Solar energy drives the global water cycle – Precipitation – Evaporation – Transpiration Water cycles between the land, oceans, and atmosphere Water cycles between the land, oceans, and atmosphere Forest destruction and irrigation affect the water cycle Forest destruction and irrigation affect the water cycle

Solar energy Net movement of water vapor by wind Evaporation from ocean Precipitation over ocean Evaporation and transpiration from land Transport over land Precipitation over land Percolation through soil Runoff and groundwater

Earth’s Water Freshwater Fresh surface water (liquid) Source: Gleick, P. H., 1996: Water resources. Distribution of Earth’s Water Freshwater – 3% Other – 0.9% Surface water – 0.3% Rivers – 2%

Runoff and Watershed Health

WATER A combination of factors threaten freshwater ecosystems Acid precipitation Acid precipitation Climate warming Climate warming Changes in land use Changes in land use

Biogeochemical Cycling of Nutrients We have a finite supply of chemical elements We have a finite supply of chemical elements Abiotic reservoir – atmosphere, rocks Abiotic reservoir – atmosphere, rocks Biotic reservoir – within organisms Biotic reservoir – within organisms Biological processing – nitrogen fixation by bacteria, carbon fixation by photosynthesis Biological processing – nitrogen fixation by bacteria, carbon fixation by photosynthesis Water cycle Water cycle Carbon cycle Carbon cycle Nitrogen cycle Nitrogen cycle Phosphorous cycle Phosphorous cycle } Local OR Global

Carbon Cycle Abiotic reservoirs = atmosphere, sedimentary rocks, dissolved carbon in oceans, and fossil fuels Abiotic reservoirs = atmosphere, sedimentary rocks, dissolved carbon in oceans, and fossil fuels – Taken from the atmosphere by photosynthesis – Used to make organic molecules – Decomposed by detritivores – Returned to the atmosphere by cellular respiration

What’s so great about carbon? It will react and bond with many other atoms. There’s a lot of it on earth The major ingredient of all organic molecules Bond to form “backbones” of macromolecules

Photosynthesis Burning of fossil fuels and wood Primary consumers Higher-level consumers Cellular respiration Detritus CO 2 in atmosphere Carbon compounds in water Decomposition

CONNECTION – Global Warming Burning of fossil fuels and wood is increasing the amount of CO 2 and other greenhouse gases in the air Burning of fossil fuels and wood is increasing the amount of CO 2 and other greenhouse gases in the air Correlation with increased global temperature Correlation with increased global temperature The greenhouse effect The greenhouse effect Natural phenomenon is essential for life on Earth Natural phenomenon is essential for life on Earth Rapidly increasing CO 2 is making global warming a danger Rapidly increasing CO 2 is making global warming a danger

Year CO 2 0 –0.15 –0.30 –0.45 Temperature Temperature variation (°C) CO 2 concentration (ppm) 320

Global warming: CO 2 lets sunlight through but retains the heat radiated from Earth. CO 2 in the atmosphere CO 2 Human activities and natural processes add CO 2 to the atmosphere, increasing the effect. Photosynthesis removes CO 2 from the atmosphere, decreasing the effect.

Biogeochemical Cycling of Nutrients We have a finite supply of chemical elements We have a finite supply of chemical elements Abiotic reservoir – atmosphere, rocks Abiotic reservoir – atmosphere, rocks Biotic reservoir – within organisms Biotic reservoir – within organisms Biological processing – nitrogen fixation by bacteria, carbon fixation by photosynthesis Biological processing – nitrogen fixation by bacteria, carbon fixation by photosynthesis Water cycle Water cycle Carbon cycle Carbon cycle Nitrogen cycle Nitrogen cycle Phosphorous cycle Phosphorous cycle } Local OR Global

Ingredient of proteins and nucleic acids Ingredient of proteins and nucleic acids Essential to the functioning and structure of all organisms Essential to the functioning and structure of all organisms Crucial for plants, but limited in quantity Crucial for plants, but limited in quantity What’s so great about nitrogen?

Nitrogen Cycle The nitrogen cycle relies heavily on bacteria Atmospheric N 2 is not available to plants Atmospheric N 2 is not available to plants – Soil bacteria convert gaseous N 2 to usable ammonium (NH 4 + ) and nitrate (NO 3 - ) – Some NH 4 + and NO 3 - are made by chemical reactions in the atmosphere

Nitrogen in atmosphere (N 2 ) Nitrogen fixation Detritivores Decomposition Assimilation by plants Denitrifying bacteria Nitrates (NO 3 – ) Nitrifying bacteria Nitrogen-fixing bacteria in root nodules of legumes Nitrogen-fixing soil bacteria Ammonium (NH 4  ) 80%

Biogeochemical Cycling of Nutrients We have a finite supply of chemical elements We have a finite supply of chemical elements Abiotic reservoir – atmosphere, rocks Abiotic reservoir – atmosphere, rocks Biotic reservoir – within organisms Biotic reservoir – within organisms Biological processing – nitrogen fixation by bacteria, carbon fixation by photosynthesis Biological processing – nitrogen fixation by bacteria, carbon fixation by photosynthesis Water cycle Water cycle Carbon cycle Carbon cycle Nitrogen cycle Nitrogen cycle Phosphorous cycle Phosphorous cycle } Local OR Global

Phosphorus is a component of nucleic acids, phospholipids, ATP, and as a mineral for bones and teeth. Phosphorus is a component of nucleic acids, phospholipids, ATP, and as a mineral for bones and teeth. What’s so great about phosphorus?

Phosphorus Cycle Depends on the weathering of rock Phosphorus and other soil minerals are recycled locally Phosphorus and other soil minerals are recycled locally Weathering of rock adds PO 4 3- to soil Weathering of rock adds PO 4 3- to soil – Slow process makes amount of phosphorus available to plants low

Runoff Sedimentation

Connections Nutrient runoff from agricultural lands and large livestock operations may cause excessive algal growth Nutrient runoff from agricultural lands and large livestock operations may cause excessive algal growth This cultural eutrophication reduces species diversity and harms water quality This cultural eutrophication reduces species diversity and harms water quality

1. Plants store starch, where is the energy in this polymer? A. In the Carbon molecules B. In the Hydrogen bonds C. In the covalent bonds which hold glucose molecules together D. In its nutrient make-up

3. A Covalent bond is formed when atoms SHARE electrons. TRUEFALSE

5. Fill in the blanks: Energy flows__________ ecosystems, while nutrients cycle ___________ ecosystems. A. Within, Through B. Through, Within

6. Approximately what percentage of energy is passed from one trophic level to the next in a food pyramid? A. 1% B. 5% C. 10% D. 100%

7. How is Carbon released back to the Atmosphere? A. Through respiration B. Through photosynthesis C. By burning fossil fuels D. All of the above E. Both A and C