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ENVI 3 energy flow in an ecosystem FINAL

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ENVI 3 energy flow in an ecosystem

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ENVI 3 energy flow in an ecosystem FINAL

  1. 1. Energy Flow in an Ecosystem Chapter 3
  2. 2. Trophic Levels  Used to locate the position or level of an organism during its energy-seeking activities.  Plants are said to belong to the first trophic level since the chemical energy they both store and utilize is one step from the original solar energy they trap.
  3. 3. Four Major Trophic Levels  Primary producers (plants, algae, bacteria)  Primary consumers (herbivores)  Secondary consumers (carnivores)  Tertiary consumers (detritivores)
  4. 4. Basic Photosynthesis
  5. 5. Cellular Respiration  Converts sugar into energy, adenosine triphosphate (ATP)
  6. 6. Food Chain  a linear network of links in a food web starting from producer organisms (such as grass or trees which use radiation from the sun to make their food) and ending at apex predator species (like grizzly bears or killer whales), detritivores (like earthworms or woodlice), or decomposer species (such as fungi or bacteria).
  7. 7. Two Basic Types of Food Chain A. Grazer Food Chain  Starts with green plants which are the producers. The producers are grazed by the herbivores which are further eaten by carnivores. B. Detritus Food Chain  Starts with dead organic matter which is eaten by other animals in the soil. A large amount of energy flows through the detritus food chain, ultimately the organic matter is decomposed
  8. 8. Two Basic Types of Food Chain A. Grazer Food Chain  Starts with green plants which are the producers. The producers are grazed by the herbivores which are further eaten by carnivores. B. Detritus Food Chain  Starts with dead organic matter which is eaten by other animals in the soil. A large amount of energy flows through the detritus food chain, ultimately the organic matter is decomposed
  9. 9. Food Chain  is a series of interconnected food chain
  10. 10. Pyramid of Energy  An energy pyramid’s shape shows how the amount of useful energy that enters each level — chemical energy in the form of food — decreases as it is used by the organisms in that level.  The consequence is that even though a lot of energy may be taken in at any level, the energy that ends up being stored there – which is the food available to the next level — is far less. Scientists have calculated that an average of 90% of the energy entering each step of the food chain is “lost” this way.
  11. 11. Pyramid of Biomass Biomass means the dry mass of living material at a stage in a food chain. The biomass goes down as you go from one stage to the next, just like the amount of energy.  A pyramid of biomass is a chart, drawn to scale, showing the biomass at each stage in a food chain. The bars become narrower as you reach the top.
  12. 12. Pyramid of Biomass Each stage in a food chain or pyramid of biomass is called a trophic level. It can be difficult to make a pyramid of biomass because:  there may be problems measuring dry biomass  an organism may belong to more than one trophic level, so it cannot easily be represented by one bar.
  13. 13. Thermodynamics  Traditionally been called the law of conservation of energy  states that energy can be transformed from one form to another, but it cannot be created or destroyed. This law suggests that all energy transfers, gains, and losses within a food web can be accounted for in an energy budget. First Law of Thermodynamics  refers to the use of heat as a convenient measurement of chemical energy in any reaction
  14. 14.  states that whenever energy is transformed, some of must be degraded into a less useful form.  In ecosystems, the biggest losses occur as heat.  explains why energy transfers are never 100% efficient. In fact, ecological efficiency, which is the amount of energy transferred from one trophic level to the next, ranges from 5-30%. On average, ecological efficiency is only about 10%. Second Law of Thermodynamics
  15. 15. Calculating Energy Efficiency  This bullock has eaten 100 kJ of stored energy in the form of grass, and excreted 63 kJ in the form of faeces, urine and gas. The energy stored in its body tissues is 4 kJ and 33 kJ has been used up in respiration.  Only 4 kJ of the original energy available to the bullock is available to the next stage, which might be humans. The efficiency of this energy transfer is:  efficiency = 4 ÷ 100 × 100 = 4%

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