Ecological pyramids ppt

Ecological pyramids ppt

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  Contents:  Ecological pyramids Types of ecological pyramids  Pyramid of numbers - Evaluating a pyramid of number  Pyramid of biomass - Evaluating a pyramid of biomass  Pyramid of energy - Evaluating a pyramid of energy  Conclusion  References
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  What are EcologicalPyramids?  Ecological pyramids are graphical representations of the trophic structure of ecosystems.  Trophic levels are the feeling position in a food chain such as primary producers, herbivores, primary carnivores, etc.
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  Types of ecologicalpyramid  Three types of ecological pyramids can usually be distinguished namely: 1. Pyramid of Numbers 2. Pyramid of Biomass 3. Pyramid of Energy
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  Pyramid of Numbers Is the graphical representation of number individuals per unit area of various trophic levels  Large numbers of producers tend to form the base  Lower numbers of top carnivores occupy the top
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  Pyramid of numbers 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.  A lesser number of herbivores, which in turn support fewer carnivores.
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  inverted + spindle-shapedpyramids
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  Evaluating the pyramidof numbers ADVANTAGES DISADVANTAGES  Simple easy method (number counting) of giving an overview  Good for comparing changes to the ecosystem at different times of year e.g. between seasons  Numbers of a specific species can be too great to measure accurately  Does not take into account ‘juvenile’ or immature forms  All organisms are included regardless of size, hence ‘inverted’ pyramids
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  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 (gm-2 or gm-3)
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  Inverted pyramid ofbiomass  In an aquatic habitat the pyramid of biomass is inverted or spindle-shaped where the biomass of trophic level depends upon the reproductive potential and longevity of the member.
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  Evaluating a pyramidof biomass ADVANTAGES DISADVANTAGES  Overcomes the problems of pyramids of number  Only uses samples from population, so 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
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  Pyramid of energy Is the graphic representation of the flow of energy through each trophic level of food chain over a fixed time period.  It is also known as “pyramid of productivity”  The input of solar energy may be indicated as an extra layer at the base.
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  Pyramid of energy Only 10% of the energy is available to next trophic level (as per Lindemann’s ten percent rule)  The energy level of each trophic level has two arts i.e. Net Production (NP) and Respiration (R) and measured in KJ m-2 yr-1
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  Evaluating a pyramidof energy ADVANTAGES DISADVANTAGES  No inverted pyramids are obtained  Shows actual energy transferred and allows for rate of production  Can compared different ecosystems based on relative energy flows  It is difficult and complex to collect energy data (rate of biomass production over time)  Problem always exists inj assigning a species to a specific trophic level
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  Conclusion  From theabove content it was clear that the ecological pyramid gives information about the trophic structures and also provides a framework for the study of ecosystem energetics along with the study of number and biomass of the organisms in the ecosystem.  Along with the brief knowledge about the trophic structures, it also allows us to observe the changes in the ecosystem due to several factors.
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  References  Ecology andEcosystem, P D Sharma  Environmental Sciences, Dr. Santilata Swain  Fath, Brian & C. Killian, Megan. (2007). The relevance of ecological pyramids in community assemblages. Ecological Modelling - ECOL MODEL. 208. 286-294. 10.1016/j.ecolmodel.2007.06.001.