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Chapter 6

Chapter 6 . Ecosystems. Outcomes. 3.2.1 Define the term biological amplification. (k) 3.2.2 Explain why there are fewer organisms at each trophic level. (Question #11 Farmer question about energy efficiency) P. 97

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Chapter 6

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  1. Chapter 6 Ecosystems

  2. Outcomes • 3.2.1 Define the term biological amplification. (k) • 3.2.2 Explain why there are fewer organisms at each trophic level. (Question #11 Farmer question about energy efficiency) P. 97 • 3.2.3 With reference to a food pyramid, explain how pesticides can reach toxic levels for organisms at a higher trophic level. (a) (question # 12. How do food pyramids help explain DDT amplification?) P. 97

  3. Food Pyramid • A Food Pyramid is a diagram showing each trophic level as a horizontal bar (p.96) • Trophic Level:The level of energy resulting after an energy transfer between organisms

  4. Food Pyramid • Producers are located on bottom & higher trophic levels are placed on top of each other; • Each bar is drawn in proportion to the mass of organisms, giving the triangle shape.

  5. Pyramid of Numbers • As we observe a food pyramid, we notice that there are fewer organisms at each increasing trophic level • Why the decrease? • less energy available at each increasing level; • fewer organisms can obtain energy to live; • therefore fewer organisms at increasing levels

  6. Pyramid of Energy • There is a high degree of energy loss at each trophic level. • The producers only store 1% of the sun's energy as food energy. • Each consumer level looses energy for several reasons: • much of the energy is lost as heat; • most of the energy is used to carry out life functions—ie. we burn many calories of energy each day. so do all organisms; • if an organism dies without being eaten the energy goes to the decomposers and not up the trophic levels; • consequently only about 10-15% of the energy is stored as usable food energy at each level

  7. Pyramid of Energy: • If we look at this in terms of units of energy & we start with 1000 units of energy at the producer level then: • the primary consumers would only have 100-150 units of food energy stored for the next level; • the secondary consumers would only have 10-15 units of food energy stored for the next trophic level; • the tertiary consumers would only have 1-1.5 units of food energy stored as food energy—it is easy to see why we do not often see a quaternary trophic level

  8. Energy Flow: Consequences • If toxic chemicals (pesticides, insecticides) are introduced at a low trophic level, they will build up through the food chain & reach amplified proportions by the time the high-order consumers join the chain • High order consumers receive a higher concentration of toxins than did the lower-level organisms

  9. Magnification of Toxin Levels (p.97) • Biological Amplificationis the term used to describe the fact that higher trophic level receive a higher dose of food chain toxins. • This problem has occurred in our environment. • The most common case was that of DDT which was first used to control insect populations in the 1950s • DDT use impacted many of the high-order carnivores throughout the world including the peregrine falcon • In Canada, DDT use was banned in the 1970s when it began showing up in human breast milk

  10. Magnification of Toxin Levels • DDT was a particularly dangerous toxin because it is fat soluble • They collect & remain in the fat tissues of animals & do not get flushed out of the body in waste water (Some poisons are water soluble and can be excreted from the system.) • Lower order organisms ingest some poison which may or may not affect them. • Higher order organisms eat large numbers of lower order organisms. A small amount in a frog becomes large in a hawk that eats 100 frogs.

  11. Section Review • What term is given to a diagram showing each trophic level as a horizontal bar where producers are located on bottom & higher trophic levels are placed on top of each other? • FOOD PYRAMID • Which level of a food Pyramid has the most food energy? • BOTTOM (PRODUCERS)

  12. Section Review • Which level of a food Pyramid has the least food energy? • TOP (THIRD ORDER CONSUMERS) • Which level of a food Pyramid has the largest number of individuals? • BOTTOM (PRODUCERS)

  13. Section Review • Which level of a food Pyramid has the smallest number of individuals? • TOP (THIRD ORDER CONSUMERS) • Which level of a food Pyramid is most in danger because of toxin magnification. • TOP (THIRD ORDER CONSUMERS) • What % of energy in a trophic level is passed onto the next level? • 10-15%

  14. Section Review • What causes the loss of energy between trophic levels? • ENERGY USED TO CARRY OUT LIFE PROCESSES & ORGANISMS NOT EATEN BY THE NEXT TROPHIC LEVEL • What term is given to the fact that higher trophic level receive higher doses of food chain toxins?  • BIOLOGICAL AMPLIFICATION

  15. Textbook • Assigned Readings • "Food pyramids" on pages 95-97 of your text book. • Assigned Activities • Complete question #11 on page 97 of your text book.

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