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Teacher Information!. Necessary materials: PowerPoint Guide If teacher has internet access, the following YouTube video would be a good tool at Slide 12 “Trophic Level Cascades Complete” at http://www.youtube.com/watch?v=yg5ieYKvYI8. Ecosystem Productivity. Principles of Ecology.

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Teacher Information!

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  1. Teacher Information! • Necessary materials: • PowerPoint Guide • If teacher has internet access, the following YouTube video would be a good tool at Slide 12 • “Trophic Level Cascades Complete” at http://www.youtube.com/watch?v=yg5ieYKvYI8

  2. Ecosystem Productivity Principles of Ecology

  3. Students will be able to… • Discuss trophic levels and energy flow in ecosystems

  4. Food chains • Definitions reviewed: • Producers autotrophs make up the base of an ecosystem • Consumers  eat other living organisms • Detrivores/decomposers  consume dead organisms and fecal wastes

  5. Primary productivity • The rate at which producers capture & store energy in their tissues • Gross = total • Net = after respiration • The most productive ecosystems in the world  estuaries, swamps, marshes, tropical rain forest

  6. Net primary production per unit area of the world’s common ecosystems

  7. Factors influencing primary productivity • Climate & nutrients • Morphology & size of organism • Rainfall • Temperature • Season • Soil (mineral & nutrient availability)

  8. Pathways of energy flow • Energy from primary productivity can flow through 2 categories of food webs • Grazing food webs • Producer  Primary consumer  Secondary consumer  tertiary consumer… • Detrital food webs • Energy flows from producers to detrivores & decomposers

  9. Trophic levels • Feeding levels with respect to primary source of energy • Producers & consumers each occupy a different trophic level • Energy is lost at each level

  10. Biomass • The total weight of all living organisms • Biomass at each trophic level  biomass pyramid 1.5 Biomass pyramid (grams/m2) Top carnivores 11 Primary carnivores 37 Herbivores 809 Detrivores/ decomposers Producers 5

  11. Energy flow pyramid • The amount of energy in each trophic level can also be estimated and plotted in a pyramid Energy flow pyramid (kcal/m2/year) 21 Top carnivores 383 Primary carnivores 3,368 Herbivores Detrivores/decomposers 20,810 Producers 5,060

  12. Why do energy and biomass decrease at higher trophic levels? • Not all biomass is consumed from one trophic level to next • Not all that is consumed is turned into biomass • Shorter food chain/web = less loss of energy • Supports idea that vegetarianism is the best way to feed a large population…

  13. Vegetarianism • Results in a decrease of human position on food chain • This won’t solve world hunger • Only 25% of earth’s land can be farmed • We need ruminants

  14. The “Cellulose Dichotomy” • Cellulose  most abundant, naturally-occuring organic molecule on earth • Humans can’t digest it • Ruminants can digest it • Cattle, sheep, goats • Deer, bison, antelope, moose, elk • “Hind-gut fermentors” can digest cellulose • Horses, rabbits, some rodents cellulose

  15. Review • Discuss trophic levels and energy flow in ecosystems

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