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Ch 54 - Ecosystems. What is an ecosystem?. All organisms in a community and the abiotic factors they interact with. Physical Laws & Energy. Law of conservation of energy – energy cannot be created or destroyed, only transferred or transformed - PowerPoint PPT Presentation
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Ch 54 - Ecosystems
What is an ecosystem?
• All organisms in a community and the abiotic factors they interact with
Physical Laws & Energy
• Law of conservation of energy – energy cannot be created or destroyed, only transferred or transformed
• 2nd law of thermodynamics – every exchange of energy increases the entropy of the universe
• Thus ecosystems need a constant supply of energy
Energy flow in ecosystems
• Energy flows through the ecosystem –one way
• Sun is primary source of energy
Trophic levels
• Autotrophs – primary producers – plants, phytoplankton
• Heterotrophs – consumers– Primary consumers – herbivores– Secondary consumers – carnivores that eat
herbivores– Tertiary consumers – carnivores that eat other
carnivores
• Decomposers/Detritivores- get energy from detritus– prokaryotes & fungi are main decomposers– Decomposition connects all trophic levels
– http://www.countrysideinfo.co.uk/rabbita.htm– http://vimeo.com/21216124
KeyChemical cyclingEnergy flow
Sun
Heat
Primary producers
Primaryconsumers
Secondary andtertiary consumers
Detritus
Microorganismsand other
detritivores
Primary production
• Most ecosystems - primary production is the amount of light energy converted to chemical energy by autotrophs during a given time period
• In a few ecosystems, chemoautotrophs are the primary producers
GPP vs. NPP
• Gross primary production – total primary production
• Net primary production:• = GPP minus energy used by primary
producers for respiration• On average NPP is ½ of GPP• This is the amount of energy available to consumers
Net primary production(kg carbon/m2yr)
3
2
0
1
Global net primary production
Primary production in Aquatic systems• Factors:
– Light limitation– Nutrient limitation
Commonly nitrogen & phosphorous
• Eutrophication– Process where bodies of water receive too many
nutrients, which results in excessive plant growth, reducing oxygen concentration & water clarity
Primary production in Terrestrial ecosystems
• Factors– Temperature– Moisture– Nutrients
Plant adaptations for nutrients
• Symbiotic relationships:• Nitrogen fixing bacteria –
– Convert N2 to NH3 – Rhizobium forms nodules on roots of
legumes
• Mycorrhizae -– Host plant provides fungus with sugar– Fungus increases surface area for water
uptake, and supplies plant with minerals absorbed from soil
Secondary production
The amount of chemical energy from food that is converted to a consumer’s biomass
Trophic efficiency
• 10% rule• Only 10% of energy available at one trophic
level is transferred to the next trophic level
• 90% of energy is not transferred:– Not eaten, lost through respiration, contained in
feces– http://science.howstuffworks.com/life/27995-assi
gnment-discovery-energy-flow-video.htm
Pyramid of energy
Biogeochemical Cycles
Matter gets recycled
Phosphorus Cycle
Carbon Cycle
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