Trophic level and_ecological_pyramids

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Trophic level and_ecological_pyramids

  1. 1. Trophic Levels & 1 Ecological PyramidsEnergy Flow in Ecosystems February 16, 2013
  2. 2. Trophic Levels 2  Each step in a food chain or food web is called a trophic level.  Primary producers always make up the first trophic level.  Various consumers occupy every other level. Some examples are shown.Energy Flow in Ecosystems February 16, 2013
  3. 3. Trophic Levels 3 Quaternary Consumers Tertiary Consumers Secondary Consumers Primary Consumers ProducersEnergy Flow in Ecosystems February 16, 2013
  4. 4. Ecological Pyramids 4  Ecological pyramids show the relative amount of energy or matter contained within each trophic level in a given food chain or food web.  There are three different types of ecological pyramids:  pyramids of energy,  pyramids of biomass, and  pyramids of numbersEnergy Flow in Ecosystems February 16, 2013
  5. 5. Ecological Pyramids 5 1. What do the three types of ecological pyramids illustrate?  Pyramids of energy show the relative amount of energy available at each trophic level.  A pyramid of biomass illustrates the relative amount of living organic matter at each trophic level.  A pyramid of numbers shows the relative number of individual organisms at each trophic level in an ecosystem.Energy Flow in Ecosystems February 16, 2013
  6. 6. 1. Pyramids of Energy 6  There is theoretically no limit to the number of trophic levels in a food web or the number of organisms that live on each level.  However, only a small portion of the energy that passes through any given trophic level is ultimately stored in the bodies of organisms at the next level.  Organisms expend much of the energy they acquire on life processes, such as respiration, movement, growth, and reproduction.  Most of the remaining energy is released into the environment as heat —a byproduct of these activities.Energy Flow in Ecosystems February 16, 2013
  7. 7. Pyramids of Energy 7  On average, about 10 percent of the energy available within one trophic level is transferred to the next trophic level (trophic efficiency)  The more levels that exist between a producer and a consumer, the smaller the percentage of the original energy from producers that is available to that consumer.Energy Flow in Ecosystems February 16, 2013
  8. 8. Pyramids of Energy 8Tertiary 10 kcalconsumersSecondary 100 kcalconsumersPrimaryconsumers 1,000 kcalProducers 10,000 kcalEnergy Flow in Ecosystems February 16, 2013
  9. 9. Pyramids of energy 9Advantages  Takes into account the PRODUCTIVITY  Addresses the fact that weight for weight, two species do not necessarily have the same energy contentDisadvantages  Very difficult to obtain data  Destructive  Problems identifying trophic levelEnergy Flow in Ecosystems February 16, 2013
  10. 10. 2. Pyramids of Biomass 10  The total amount of living tissue within a given trophic level is called its biomass.  The amount of biomass a given trophic level can support is determined, in part, by the amount of energy available.Energy Flow in Ecosystems February 16, 2013
  11. 11. 2. Pyramids of Biomass 11  Illustrates the relative amount of living organic matter at each trophic level.  Indicates the total dry mass of the organisms in each trophic level  Typically, the greatest biomass is at the base of the pyramid, as is seen in the field ecosystem modeled here.Energy Flow in Ecosystems February 16, 2013
  12. 12. Pyramids of Biomass 12 How might this data be  Advantages collected?  The data is more accurate.  Eliminates misleadinga) Individual organisms problems of producer size weighed and counted. differencesb) Dry mass should be  Disadvantages compared to eliminate  Laborious and expensive errors due to water content  Destructive  Can also be misleading in some circumstancesEnergy Flow in Ecosystems February 16, 2013
  13. 13. 3. Pyramids of Numbers 13  A pyramid of numbers shows the relative number of individual organisms at each trophic level in an ecosystem. 3rd level carnivore 2nd level carnivore 1st level Carnivore Herbivores Producers Log numbersEnergy Flow in Ecosystems February 16, 2013
  14. 14. 3. Pyramids of Numbers 14 In most ecosystems, the shape of the pyramid of numbers is similar to the shape of the pyramid of biomass for the same ecosystem, with the numbers of individuals on each level decreasing from the level below it.Energy Flow in Ecosystems February 16, 2013
  15. 15. 3. Pyramids of Numbers 15  In some cases, however, consumers are much smaller than organisms they feed upon.  Thousands of insects may graze on a single tree, for example. The tree has a lot of biomass, but represents only one organism.  In such cases, the pyramid of numbers may be turned upside down, but the pyramid of biomass usually still has the normal orientation. 2nd level carnivore 1st level carnivore herbivores Producers numbersEnergy Flow in Ecosystems February 16, 2013
  16. 16. Pyramids of Number 16 Advantage  Data relatively easy to collect using simple sampling Disadvantages  Producers vary in size  Large range of numbers  Trophic level difficult to work outEnergy Flow in Ecosystems February 16, 2013

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