Bio1 Ecosystems Small

8/8/2019 Bio1 Ecosystems Small

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Ecosystems


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EcosystemsAll the organisms living in a communityas well as all the abiotic factors withwhich they interact.


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B oth energy andB oth energy andmatter movematter movethrough ecologicalthrough ecologicalcommunitiescommunities

Energy flow (dottedEnergy flow (dotted

red lines) isred lines) isunidirectional. Energyunidirectional. Energychanges form andchanges form anddissipates.dissipates.

Nutrients change formNutrients change formand cycle throughand cycle throughecosystems (solid blueecosystems (solid bluelines).lines).


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Energy reviewFirst law of thermodynamics Energy cannot be created or destroyed It can be converted to other forms


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Energy review

Second law of thermodynamics There is loss of energy with conversion,

usually in the form of heat The heat energy still exists, but cannot be

used


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Energy on Earth

Most of Earths energycomes from the sun

Some of Earths inhabitantshave adapted to convertsolar energy to chemicalpotential energy (in carbonbonds).


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Energy on Earth

Most of Earths energycomes from the sun

Some of Earths inhabitantshave adapted to convertsolar energy to chemicalpotential energy (in carbonbonds).

The primary producersgross primary production (GPP)-the total amount of biomass produced by allautotrophs in the community

net primary production ( NPP) GPP less biomass the autotrophs use to meettheir own metabolic needs


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W hat controls primary

productivity?Global trends in primaryproduction

Terrestrial ecosystems are moreproductive (101 X 10 ^9 tons of fixedcarbon v. 61 X 10^9 tones in aquaticecosystems)

There is generally higher productivity inthe tropics


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Terrestrial primary productiongenerally increases with moistureand temperature

Rosenwitz studied net primaryproduction across biomes

Compare NPP to actual

evapotranspiration


productivity?


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Terrestrial and aquatic primaryproduction is also limited by nutrientavailability


productivity?


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From primary to secondary

productivity


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productivityThe amount of chemical energy in

a consumers foodthat is converted totheir own newbiomass


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productivityOn average only10% of the energyfrom one level willreach the levelabove it (trophicefficiency)


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productivityTransfer efficienciesare low becauseenergy is lost due

to cellular respiration andwhen food cannotbe assimilated


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W hats missing?Decomposers-consumers who get their energy from detritus.They are importantnutrient cyclers (helpreturn nutrients to plants)

Energy flows, nutrientscycle


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T he cycling of nutrientsT he cycling of nutrientswithin ecosystemswithin ecosystems

Life on Earth depends on recyclingessential chemical elements.

Biogeochemical cycles move elementsbetween the atmosphere, hydrosphere,lithosphere, and biosphere.


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The water cycleW ater is essential toall living thingsTypically found inoceans, lakes, rivers,ice caps, groundwater (small amount inatmosphere)Cycles viasublimation,

precipitation,evaporation,condensation,consumption,transpiration


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Human impacts on ecosystems Agriculture

Displaces communitiesMoves nutrients

aroundAfter soils are depletedof nutrients, fertilizer must be added

Huge source of nitrogen to the Earth Has led to

eutrophication


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Human impacts on ecosystemsBurning of fossil isaltering the carboncycle

More CO 2 in theatmosphere

Plants growingdifferently with elevatedCO 2

Also affecting other cycles through climatechange


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Summary

You should understand how energy flows andnutrients cycle through ecosystemsYou should understand what limits primaryproductivityYou should understand why energy is lost atas you move up each trophic levelYou should understand how humans have

impacted the carbon and nitrogen cycles

Bio1 Ecosystems Small

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