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

The Earth’s Spheres 1. The hydrosphere is the zone of water that covers over three-quarters of the earth.             a. The ability of water to absorb and release great quantities of heat keeps climate within livable range. 2. The atmosphere is the gaseous layer near earth.             a. The atmosphere is concentrated in lowest 10 kilometers; extends thinly out to 1,000 km.             b. Major gases are nitrogen, oxygen and carbon dioxide.             3. The lithosphere is a rocky substratum that extends about 100 kilometers deep.             a. Weathering of rocks supplies minerals to plants and eventually forms soil.             b. Soil contains decayed organic material (humus) that recycles nutrients to plants. 4. The biosphere is the thin layer where life is possible between the outer atmosphere and the lithosphere.

Ecosystems can range from a microcosm, such as an aquarium To a large area such as a lake or forest Regardless of an ecosystem’s size Its dynamics involve two main processes: energy flow and chemical cycling Energy flows through ecosystems While matter cycles within them

Factors affecting Ecosystems Biotic: Living Abiotic: Nonliving Clip

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

Energy flows through an ecosystem First law of thermodynamics energy can neither be created nor destroyed; it can only be changed from one form of energy to another. Energy in an ecosystem is transformed by the organism and passed through the food chains Second law of thermodynamics: when energy is transformed from one form to another, there is always some loss of energy from the system, usually as low grade heat.

A terrestrial food chain Energy flows through an ecosystem: Food Chains and Webs A food chain represents passage of energy through populations in a community. A trophic level is a feeding level of one or more populations in a food web. All levels connect to decomposers Quaternary consumers Tertiary consumers Secondary consumers Primary consumers Primary producers Carnivore Herbivore Plant Zooplankton Phytoplankton A terrestrial food chain A marine food chain Animation

Smaller toothed whales Energy flows through an ecosystem: Humans Baleen whales Crab-eater seals Birds Fishes Squids Leopard seals Elephant Smaller toothed whales Sperm whales Carnivorous plankton Euphausids (krill) Copepods Phyto- plankton Food Webs A food web Is a branching food chain with complex trophic interactions

Ecological Pyramids Shows the trophic structure of an ecosystem and the energy content that is passed to each successive trophic level in a food web. Pyramid of energy All of the solar energy that enters an ecosystem is eventually lost as heat

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

Primary productivity Rate at which autotrophs capture and store energy within organic compounds over a length of time. i.e. Amount of light energy converted to chemical energy (glucose) Net primary production (NPP) Is equal to GPP minus the energy used by the primary producers for respiration Only NPP Is available to consumers

Measuring Primary Productivity Rate of O2 production Gross primary productivity is the amount available to heterotrophs GPP is NPP + R Since some of the O2 is used in respiration: NPP= GPP - R

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%

Biological Magnification PCBs: polychlorinated biphenyls Concentration of PCBs Herring gull eggs 124 ppm Zooplankton 0.123 ppm Phytoplankton 0.025 ppm Lake trout 4.83 ppm Smelt 1.04 ppm Organisms at higher trophic levels have greater concentrations of accumulated toxins stored in their bodies. Ex: bald eagle -1950s -DDT DDT interferes with the deposition of calcium in eggshells DDT is now outlawed

Biogeochemical Cycles Life on Earth Depends on the recycling of essential chemical elements Nutrient circuits that cycle matter through an ecosystem Involve both biotic and abiotic components and are often called biogeochemical cycles Hydrologic cycle Carbon Cycle Nitrogen cycle Phosphorus cycle Clip

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