Ch 55 Ecosystems Jeff Jewett ACS June 2010 Ver 1

Ecosystem

• Sum of all organisms in an area AND all the abiotic factors with which they interact

• Communities PLUS abiotic factors

• Boundaries are rarely clear-cut, may depend on scale of question

Ch 55 Key Topics

• Conservation of Energy/Mass

• GPP/NPP and limitations

• Energy Transfer pyramids of energy/biomass

• Biogeochemical Cycles (C, N, H 2 0)

• Human impact on biogeo. Cycles

• • Global warming, eutrophication, biomagnification, acid rain, ozone hole

Energy Flows, Matter Cycles

• Energy enters (usually as sunlight)

• Converted to biomass (chemical energy) by autotrophs

• Passed to heterotrophs (incl. decomposers)

• Dissipated as heat

Energy Flows, Matter Cycles (2)

• Chemical elements (C, N, P) are cycled between abiotic and biotic parts of ecosystem (Law of Conservation of Mass)

• Matter continuously cycles (not created or destroyed)

• 2 nd law of Thermodynamics:

• Energy conversions are never 100% efficient, therefore some is always lost as heat

• Ecosystems require constant input of energy

Trophic Levels

• Autotrophs = primary producers (redundant)

• • Photoautotrophs rely on light for energy (by FAR the most common)

• • Chemoautotrophs oxidize naturally occuring inorganic compounds as fuel (common in hot springs, deep-sea volcanic vents)

• All of the ecosystem depends on autotrophs!

Trophic Levels (2)

• Heterotrophs

• • depend directly or indirectly on autotrophs

• • eat things that are alive or were alive

• • Consumers & decomposers (detritivores)

• • Detritivores fungus, bacteria, insects (FBI) eat detritus (non-living organic material such as feces, dead critters, fallen leaves, wood)

• • Consumers primary, secondary, tertiary, quarternary (higher levels rare)

http://image.tutorvista.com/content/ecosystem/food-web-terrestrial-aquatic-ecosystem.jpeg

55.2 Energy GPP

• Gross Primary Production (GPP) = Amount of light energy converted to chemical energy (sugars) per time (rate of photosynthesis)

• Some of this energy is used by the plant for life (cellular respiration)

• Some is converted into biomass, such as starch storage or structural components (new growth)

NPP a very important ecological statistic!

• Net Primary Productivity amount of sugars left over after respiration, per unit time (rate of new biomass production)

• NPP = GPP R

• Value of NPP gives the size of the base of the food chain (how much total food is there for consumers?)

• NPP highest where it is warm/wet

• (tropical rainforest)

Global NPP, 2008 NASA Earth Observatory: http://earthobservatory.nasa.gov/IOTD/view.php?id=38889

June NPP http://www.uwsp.edu/geo/faculty/lemke/geog101/images/14c_npp_junemap_nasa.jpg

December NPP http://www.uwsp.edu/geo/faculty/lemke/geog101/images/14e_npp_decmap_nasa.jpg

Human Appropriation of NPP

• SKIP THIS SLIDE

http://sedac.ciesin.columbia.edu/es/hanpp.html http://earthobservatory.nasa.gov/Features/HANPP/hanpp.php

Aquatic NPP Limitation

• Light -