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Food Chains & Food Webs

Food Chains & Food Webs. Food Chain vs. Food Web- What’s the difference?. A food chain is a diagram that shows a step-by-step sequence of who eats whom in an ecosystem.

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Food Chains & Food Webs

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  1. Food Chains & Food Webs

  2. Food Chain vs. Food Web- What’s the difference? • A food chain is a diagram that shows a step-by-step sequence of who eats whom in an ecosystem. • A food web is a diagram that shows many possible food chains or feeding relationships that can involve any combination of the individuals in an ecosystem. • The arrows in chains and webs always point to the organism doing the eating (Follow the Energy)

  3. Which are the herbivores? Carnivores? What is the significance of the arrows? Why are decomposers important in a food chain?

  4. Trophic Levels • Each member of the food chain occupies a specific trophic level and describes how an organism obtains its energy. • The first trophic level is the primary producer • (e.g. plants) – converts energy from the sun • The second trophic level is the primaryconsumer • (e.g. herbivores) • The third trophic level is the secondary consumer • (e.g. omnivores or carnivores)

  5. Can more than one organism occupy a trophic level? YES!

  6. How do trophic levels differ? • The first trophic level houses the largest amount of energy. • Each subsequent trophic level only houses 10 percent of the energy from the previous level • (i.e. 90% is lost) • Why is energy lost at each level? • Not all of the organism is consumed. • Not everything that is eaten is digested. • Energy is lost as heat from the bodies of organisms. • What do changes in trophic levels look like as you move up through the food chain?

  7. Food Pyramids • Food Pyramids display the distribution of organisms in a food chain through: • Numbers of organisms at each trophic level. • Biomass (kg) of organisms at each trophic level. • Energy (kJ) available at each trophic level.

  8. Pyramid of Numbers

  9. Pyramid of Biomass

  10. Pyramid of Energy • 2nd Law of Thermodynamics: • In every energy transformation, • some energy is always lost • There is no 100% energy conversion

  11. Ecological Pyramids

  12. Homework • Worksheets BLMs 1-9 & 1-10 • Read 1.2 in the textbook • Do pg. 27 # 4-6

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