Ecosystems

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

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

Ecosystem inputs nutrients cycle inputs energy nutrients biosphere energy flows through constant input of energy nutrients cycle Matter cannot be created or destroyed Don’t forget the laws of Physics! nutrients can only cycle inputs energy nutrients

Food chains Trophic levels sun feeding relationships Tertiary consumer Trophic levels feeding relationships start with energy from the sun captured by plants 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

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

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

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

Humans in food chains Energy dynamics of ecosystems have important implications for human populations How much energy is available if we are: carnivores? vegetarians? Seems to be easier/cheaper to support a large population on grain than on beef! For example if a man needs 3,000 Calories per day, then 30,000 Cal beef are needed, which in turn need 300,000 Cal of corn, which in turn means 30,000,000 Cal of sunshine. This works out to be 1.5 acres of corn per day per person. If the person ate corn directly then 10 people could be supported by the same 1.5 acres of corn.

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

Ecosystems with greater productivity have more sunlight, water and nutrients.

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

Sample problem #1 Total energy output? .75 kcal How much is used to build biomass or Secondary Production? .05 kcal What % is not being efficiently used for biomass? 93%

Sample problem #2 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 consumed = 100 kcal Lost and Respired: 35 + 50 = 85 kcal Total energy for growth: 15 kcal Efficiency (%) = 15/100 = .15 or 15%

Generalized Nutrient cycling consumers consumers consumers producers decomposers decomposers nutrients ENTER FOOD CHAIN = made available to producers nutrients made available to producers return to abiotic reservoir Decomposition connects all trophic levels abiotic reservoir abiotic reservoir geologic processes geologic processes

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

Nitrogen cycle Atmospheric nitrogen Carnivores Herbivores Birds Plants 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 Plankton with nitrogen-fixing bacteria Plants Death, excretion, feces Fish Nitrogen-fixing bacteria (plant roots) Decomposing bacteria amino acids excretion Ammonifying bacteria Nitrogen-fixing bacteria (soil) loss to deep sediments Nitrifying bacteria Denitrifying bacteria soil nitrates

Phosphorus cycle Land Plants animals Animal tissue and feces Urine 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 Aquatic animals Plants and algae Precipitates Loss to deep sediment

Water cycle Solar energy Transpiration Evaporation Precipitation 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

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

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

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