Ch 54 - Ecosystems

1. Ch 54 - Ecosystems

2. What is an ecosystem? • All organisms in a community and the abiotic factors they interact with

3. 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

4. Energy flow in ecosystems • Energy flows through the ecosystem –one way • Sun is primary source of energy

5. 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

6. 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

7. Sun Key Chemical cycling Energy flow Heat Primary producers Primaryconsumers Detritus Microorganismsand otherdetritivores Secondary andtertiary consumers

8. 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

9. 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

10. Global net primary production Net primary production(kg carbon/m2yr) 3 2 1 0

11. 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

12. Primary production in Terrestrial ecosystems • Factors • Temperature • Moisture • Nutrients

13. 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

14. Secondary production The amount of chemical energy from food that is converted to a consumer’s biomass

15. 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-assignment-discovery-energy-flow-video.htm

17. Pyramid of energy

19. Biogeochemical Cycles Matter gets recycled

20. PhosphorusCycle

23. Carbon Cycle