Understanding Ecosystem Dynamics: Energy Flow and Nutrient Cycling

1. Ecosystems

2. Studying organisms in their environment biosphere ecosystem community population organism

3. Essential Questions: • What limits the production in ecosystems? • How do nutrients move in the ecosystem? • How does energy move through the ecosystem?

4. Ecosystem • All the organisms in a community plus abiotic factors • ecosystems are transformers of energy& processors of matter • Ecosystems are self-sustaining • what is needed? • capture energy • transfer energy • cycle nutrients

5. Ecosystem inputs biosphere constant inputof energy energy flowsthrough nutrients cycle Don’t forgetthe laws of Physics! Matter cannot be created ordestroyed nutrients can only cycle inputs • energy • nutrients

6. Decompositionconnects all trophic levels Generalized Nutrient cycling consumers consumers producers consumers decomposers decomposers nutrientsENTER FOOD CHAIN= made availableto producers nutrientsmade availableto producers return toabioticreservoir abioticreservoir abioticreservoir geologicprocesses geologicprocesses

7. CO2 in atmosphere Combustion of fuels Industry and home Photosynthesis Diffusion Respiration Plants Animals Dissolved CO2 Bicarbonates Photosynthesis Deposition of dead material Animals Plants and algae Fossil fuels (oil, gas, coal) Deposition of dead material Carbonates in sediment Carbon cycle • abiotic reservoir: • CO2 in atmosphere • enter food chain: • photosynthesis = carbon fixation in Calvin cycle • recycle: • return to abiotic: • respiration • combustion

8. abiotic reservoir: • N in atmosphere • enter food chain: • nitrogen fixation by soil & aquatic bacteria • recycle: • decomposing & nitrifying bacteria • return to abiotic: • denitrifying bacteria Nitrogen cycle Atmospheric nitrogen Carnivores Herbivores Birds Plants Plankton with nitrogen-fixing bacteria Death, excretion, feces Nitrogen-fixing bacteria (plant roots) Fish Decomposing bacteria amino acids excretion Nitrogen-fixing bacteria (soil) Ammonifying bacteria loss to deep sediments Nitrifying bacteria Denitrifying bacteria soil nitrates

9. abiotic reservoir: • rocks, minerals, soil enter food chain: • erosion releases soluble phosphate • uptake by plants recycle: • decomposing bacteria & fungi return to abiotic: • loss to ocean sediment Phosphorus cycle Land animals Plants Animal tissue and feces Urine Soluble soil phosphate Decomposers (bacteria and fungi) Loss in drainage Rocks and minerals Phosphates in solution Decomposers (bacteria & fungi) Animal tissue and feces Plants and algae Aquatic animals Precipitates Loss to deep sediment

10. abiotic reservoir: • surface & atmospheric water enter food chain: • precipitation & plant uptake recycle: • transpiration return to abiotic: • evaporation & runoff Water cycle Solar energy Transpiration Water vapor Evaporation Precipitation Oceans Runoff Lakes Percolation in soil Aquifer Groundwater

11. Transpiration Why does water flow into, up and out of a plant? We will discuss process in detail soon!

12. Breaking the water cycle • Deforestation breaks the water cycle • groundwater is not transpired to the atmosphere, so precipitation is not created forest  desert desertification

13. Effects of deforestation 40% increase in runoff • loss of water • 60x loss in nitrogen • 10x loss in calcium loss into surface water nitrate levels in runoff 80 40 loss out of ecosystem! Concentration of nitrate (mg/l ) 4 Deforestation 2 Why isnitrogen soimportant? 0 1965 1966 1967 1968 Year

14. loss of energy loss of energy Energy flows through ecosystems sun secondary consumers (carnivores) primary consumers (herbivores) Energy is incorporated into a community by what group? producers (plants)

15. Productivity • Primary productivity: Term for the rate which producers photosynthesize organic compounds in an ecosystem. • Gross primary productivity: total amount of photosynthetic biomass production in an ecosystem • Net Primary Productivity = GPP – respiration cost

16. Ecosystems with greater productivity are more stable and diverse than ecosystems with less productivity. • Which ecosystems are most productive?

17. sun energy lost todaily living energy lost todaily living Inefficiency of energy transfer • Loss of energy between levels of food chain • To where is the energy lost? The cost of living! 17% growth only this energymoves on to the next level in the food chain 33% cellular respiration 50% waste (feces)

18. sun Level 4 Tertiary consumer Food chains • Trophic levels • feeding relationships • start with energy from the sun • captured byplants • 1st level of all food chains • food chains usually go up only 4 or 5 levels • inefficiency of energy transfer • all levels connect to decomposers top carnivore Level 3 Secondary consumer carnivore Level 2 Primary consumer heterotrophs herbivore Level 1 Producer autotrophs Fungi Decomposers Bacteria

19. Producers & Decomposers • Producers move matter from abiotic sources (air/soil) to biotic sources (food web) • Decomposers move matter from biotic sources to abiotic sources

20. sun Ecological pyramid • Loss of energy between levels of food chain • can feed fewer animals in each level 10% energy available for next level Notice only 1% of sunlight energy converted by plants

21. Humans in food chains • Dynamics of energy through ecosystems have important implications for human populations • how much energy does it take to feed a human? • if we are meat eaters? • if we are vegetarian?

22. What you need to be able to do: • Using the laws of conservation of matter and energy to do some basic accounting and determine different aspects of energy and matter usage in a community. • Remember: Inputs have to equal outputs

23. Sample problem • A caterpillar consumes 100 kcal of energy. It uses 35 kcal for cell respiration, and loses 50 kcal as waste. Determine the trophic efficiency for its creation of new biomass. • Total energy = 100 kcal • Lost and Respired: 35 + 50 = 85 kcal • Total energy for growth: 15 kcal • Efficiency = part/total = 15/100 = .15 (or 15% or 3/20 as fraction)