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By the end of this session I should be able to:

By the end of this session I should be able to:. (a) define the term ecosystem ; ( b) state that ecosystems are dynamic systems; ( c) define the terms biotic factor and abiotic factor , using named examples; ( d) define the terms producer, consumer decomposer and trophic level ;

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By the end of this session I should be able to:

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  1. By the end of this session I should be able to: (a) define the term ecosystem; (b) state that ecosystems are dynamic systems; (c) define the terms biotic factor and abiotic factor, using named examples; (d) define the terms producer, consumer decomposer and trophic level; (e) describe how energy is transferred though ecosystems; (f) outline how energy transfers between trophic levels can be measured; (g) discuss the efficiency of energy transfers between trophic levels; (h) explain how human activities can manipulate the flow of energy through ecosystems (HSW6b);

  2. On the piece of paper in front of you there are 10 different ecosystems. Name as many as you can by labelling the pictures and adding the selection pressure that would have the biggest effect on the organisms living there.

  3. What is lurking in your eyelashes?

  4. Use your texts to complete the following

  5. What selection pressures does Ethan have to cope with? Think biotic and abiotic factors.

  6. Biotic  living / Abiotic  non living

  7. What limits the length of the food chain?

  8. What limits length of food chain? • H1: Energetics • Availability of energy limits to 5-7 levels • Depends on: NPP energy needed by consumers average ecological efficiency • H2: Dynamic stability Longer chains less stable because: Fluctuations at lower trophic levels magnified at higher levels ---> extinction of top predators.

  9. A food web is a branching food chain with complex trophic interactions • Species may play a role at more than one trophic level • Food webs can be simplified by isolating a portion of a community that interacts very little with the rest of the community

  10. How heterotrophs use food energy Energy loss in an ecosystem Biomass available at the next trophic level • About one order of magnitude of available energy is lost from one trophic level to the next • Reason why food chains generally consist of only 3 or 4 steps Cayuga Lake In NY

  11. How can we calculate the amount of energy? each trophic level? Consumers (heterotrophs) Producers (autotrophs)

  12. How is energy lost between trophic level?

  13. Primary productivity • Gross Primary Productivity (GPP): • total amount of photosynthetic energy captured in a given period of time. • Net Primary Productivity (NPP): • the amount of plant biomass (energy) after cell respiration has occurred in plant tissues. NPP = GPP – Plant respiration plant growth/ total photosynthesis/ unit area/ unit area/unit time unit time

  14. Primary productivity – marine ecosystems

  15. Global variation in estimatedNPP Figure 9

  16. Mr Moore set the homework on ‘increasing efficiency in the production of food by manipulating trophic levels’

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