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Ecological PyramidsA key to understanding the structure and function of                   ecosystems
What are Ecological     Pyramids?• Ecological pyramids are graphical  representations of the trophic structure of  ecosyst...
Types of ecological         pyramid  Three types of ecological pyramids can  usually be distinguished namely:• Pyramid of ...
Pyramid of numbers• Is the graphic representation of number of individuals per unit area of various trophic levels• Large ...
Pyramid of numbers -             example• The shape of the pyramid of numbers vary from ecosystem to ecosystem.• In aquati...
‘inverted’ + ‘spindle-   shaped pyramids
Evaluating the pyramid of numbers        ADVANTAGES                      DISADVANTAGES                                   N...
Pyramid of biomass• Is the graphic representation of  biomass present per unit area of  different trophic levels, with  pr...
Inverted pyramid of             biomassIn an aquatic habitat the pyramidof biomass is inverted or spindleshaped where the ...
Evaluating a pyramid of biomass        ADVANTAGES                           DISADVANTAGESOvercomes the problems of pyramid...
pyramid of productivityPyramid of productivity is agraphic representation of theflow of energy through eachtrophic level of...
pyramid of productivity                                          The energy level of each trophic levelOnly 10% of the ene...
pyramid of productivity        Advantages                    Disadvantages                                It is difficult a...
consequences of ecological pyramids and         ecosystem function•   Bioaccumulation - when plants / animals take up a   ...
consequences of ecological pyramids and         ecosystem function•   Biomagnification - refers to the sequence of processe...
There are many pollutants like the DDT that                                                are not bio-degradable. These a...
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Ecological pyramids

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  • You must be familiar with the shape of a pyramid. The base of a pyramid is broad and it narrows down at the apex. One gets a similar shape, whether you express the food or energy relationship between organisms at different trophic level. Thus, relationship is expressed in terms of number, biomass or energy. http://kshitij-school.com/Study-Material/Class-12/Biology/Ecosystem/Ecological-pyramids.aspx
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Ecological pyramids

  1. 1. Ecological PyramidsA key to understanding the structure and function of ecosystems
  2. 2. What are Ecological Pyramids?• Ecological pyramids are graphical representations of the trophic structure of ecosystems.• Trophic levels are the feeding position in a food chain such as primary producers, herbivore, primary carnivore, etc.
  3. 3. Types of ecological pyramid Three types of ecological pyramids can usually be distinguished namely:• Pyramid of numbers• Pyramid of biomass• Pyramid of productivity
  4. 4. Pyramid of numbers• Is the graphic representation of number of individuals per unit area of various trophic levels• Large numbers of producers tend to form the base• Lower numbers of top carnivores occupy the tip Pyramid of Numbers in a Grassland Ecosystem
  5. 5. Pyramid of numbers - example• The shape of the pyramid of numbers vary from ecosystem to ecosystem.• In aquatic ecosystems and grassland communities, autotrophs are present in large numbers per unit area.• They support a lesser number of herbivores, which in turn support fewer Pyramid of Numbers in a Aquatic Ecosystem carnivores.
  6. 6. ‘inverted’ + ‘spindle- shaped pyramids
  7. 7. Evaluating the pyramid of numbers ADVANTAGES DISADVANTAGES Numbers of a specific species Simple easy method (number can be too great to measurecounting) of giving an overview accuratelyGood for comparing changes to Does not take into accountthe ecosystem at different times ‘juveniles’ or immature forms of year e.g. between seasons All organisms are included regardless of size, hence ‘inverted’ pyramids
  8. 8. Pyramid of biomass• Is the graphic representation of biomass present per unit area of different trophic levels, with producers at the base and top carnivores at the tip.• Biomass is calculated by the mass of each individual x number of individuals at each trophic level (g m-2 or g m-3)
  9. 9. Inverted pyramid of biomassIn an aquatic habitat the pyramidof biomass is inverted or spindleshaped where the biomass oftrophic level depends upon thereproductive potential andlongevity of the member.
  10. 10. Evaluating a pyramid of biomass ADVANTAGES DISADVANTAGESOvercomes the problems of pyramids Only uses samples from populations, so of number difficult to measure biomass exactly Time of year that biomass is measured influences result e.g. trees in summer Organisms of the same size do not necessarily have the same energy content Inverted’ pyramids may result from producers with high turnover rate
  11. 11. pyramid of productivityPyramid of productivity is agraphic representation of theflow of energy through eachtrophic level of a food chainover a fixed time period. Theinput of solar energy may beindicated as an extra layer atthe base.
  12. 12. pyramid of productivity The energy level of each trophic levelOnly 10% of the energy is available to has two arts i.e. Net Production (NP)next trophic level (as per Lindemanns and Respiration (R) and is measured in ten percent rule). KJ m-2 yr-1
  13. 13. pyramid of productivity Advantages Disadvantages It is difficult and complex to No inverted pyramids are collect energy data (rate of obtained biomass production over time Shows actual energy Problem required) is always exists in transferred and allows for assigning a species to a rate of production specific trophic level, Can compared different especially omnivoresecosystems based on relative energy flows
  14. 14. consequences of ecological pyramids and ecosystem function• Bioaccumulation - when plants / animals take up a chemical from the environment and do not excrete it. The chemical builds up in the organism over time to a potentially lethal level.
  15. 15. consequences of ecological pyramids and ecosystem function• Biomagnification - refers to the sequence of processes that results in higher concentrations of the chemical in organisms at higher levels in the food chain (at higher trophic levels). In this way the chemical’s concentration is magnified from trophic level to trophic level. The concentration of the chemical may not affect lower levels of the food chain but the top levels take in so much it can cause disease or death.
  16. 16. There are many pollutants like the DDT that are not bio-degradable. These accumulate in the organisms and cause serious health problems. The contamination of water with these pollutants results in their entry into the microscopic plants and animals. These organisms are fed upon by higher aquatic life like the fish. The fish in turn are fed upon by the land animals including man.Thus, the pollutant reaches the body of man. At each step in the food chain, the contaminantincreases in quantity. This is because a fish feeds on large quantity of smaller plants and man eatsfish. These contaminants like DDT remain in the fats and are not degraded in the body. Over theyears the amount of DDT increases in the body. This is called biomagnification.

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