Published on


Published in: Education


  2. 2. An “Ecological System?” In the discipline of ecology, the wordEcosystem is an abbreviation of the term, Sir Arthur Tansley (1871-1955)ecological system – the basic unit in ecology. It firstappeared in a 1935 publication by the British ecologist ArthurTansley (Tansley, 1935). However, the term had been coinedalready in 1930 by Tansleys colleague Roy Clapham, who wasasked if he could think of a suitable word to denote the physicaland biological components of an environment considered inrelation to each other as a unit. Tansley, A., 1935, The use of vegetational concepts and terms. Ecology, v. 16, p. 284-307.
  3. 3. An “Ecological System?” Components of an Ecosystem: Sir Arthur Tansley (1871-1955) Abiotic (non-living) and Biotic Components Physical Components Species Water Populations Nutrients Communities Topography WeatherCompetition and Predation Disturbances
  4. 4. What Keeps Us and Other Organisms Alive?• One-way flow of high-quality energy from the sun (returned as low quality heat)• Cycling of matter or nutrients through parts of the biosphere (closed system applies; law of conservation of matter; time frame of seconds to centuries)• Gravity (maintains atmosphere, enables movement & cycling of air, water, nutrients)
  5. 5. Energy and the Laws of Thermodynamics 20.1 – The Laws of Thermodynamics Govern Energy Flow. Energy exists in many forms, such as heat, light, chemicalenergy, and electrical energy. Energy is the ability to bringabout change or to do work. Thermodynamics is the studyof energy. Kinetic energyEntropy Entropy Potential energy
  6. 6. Energy and the Laws of ThermodynamicsThe 1st Law of Thermodynamics:Energy can be changed from one form toanother, but it cannot be created ordestroyed. The total amount of energyand matter in the Universe remainsconstant, merely changing from one formto another. Isaac Newton (1643-1727)
  7. 7. Energy and the Laws of ThermodynamicsThe 2nd Law ofThermodynamics: "in all energyexchanges, if no energy enters or leaves thesystem, the potential energy of the state willalways be less than that of the initial state." Inenergy transfer, some energy will dissipateas heat. The flow of energy maintains Isaac Newton (1643-1727)order of life.
  8. 8. Second Law of Thermodynamics• - Scientists have studied many ecosystems and have concluded that this energy loss is a constant pattern. In fact, scientists have calculated that the percentage (%) of usable energy transferred from one organism to another is 10%.• !! - That means that 90% of energy is lost as heat!!!• So…. if producers captured 10,000 calories from the sun, then only bout 1,000 calories will be available to support primary consumers (herbivores), and only about 100 calories to support secondary consumers (carnivores or omnivores).
  9. 9. 10% LAW.. !!• In the Arctic, Eskimos hunt whales for food. Whales eat tons and tons of microscopic plankton. This plankton in turn eats microscopic algae. It requires 1,000 units of energy (calories) of algae to produce 100 calories of plankton which is what a whale uses to produce 10 calories of blubber (fat) to its body. Finally these 10 calories of whale blubber contains enough energy to give the Eskimo one calorie of energy.
  10. 10. Trophic Levels• Producers – autotrophs-Photosynthesis• Consumers – heterotrophs-Primary-Secondary-Third-level• Omnivores• Detritus feeders / Decomposers
  11. 11. Trophic Levels Trophic Level = Feeding Level 20 energy 10 consumer energy Producers energy- Just like a skyscraperhas floors, or levels, anenergy Pyramid hasdistinct levels, calledTROPHIC LEVELS.
  12. 12. 4th Tr. Level 1 calorie eskimos 3rd Trophic Level 10 calories whales 2nd Trophic Level 100 calories plankton 1st Trophic Level 1000 calories algaeA healthy ecosystem will always havethe most energy available in the first trophiclevel.
  13. 13. Ecosystem Energetics- Energy Decreases in Each Successive Trophic Level.
  14. 14. Ecological pyramids• The standing crop, productivity, number of organisms, etc. of an ecosystem can be conveniently depicted using “pyramids”, where the size of each compartment represents the amount of the item in each trophic level of a food chain. carnivores herbivores producers Note that the complexities of the interactions in a food web are not shown in a pyramid; but, pyramids are often useful conceptual devices--they give one a sense of the overall form of the trophic structure of an ecosystem.
  15. 15. Pyramid of energy• A pyramid of energy depicts the energy flow, or productivity, of each trophic level.• Due to the Laws of Thermodynamics, each higher level must be smaller than lower levels, due to loss of some energy as heat (via respiration) within each level. carnivores herbivores producers
  16. 16. Pyramids of Energy Suggests:• The number of trophic levels are limited. At each trophic level, there is a dramatic reduction in energy.• Eating at lower trophic levels means more resources available.• Movement up the pyramid explains the problems of Biological Magnification (DDT, PCBs, etc.)
  17. 17. Food Chains and Food WebsHow energy moves in an ecosystem OR who eats who!? ;)
  18. 18. • Food Chain: A food chain shows one path of how energy moves through an ecosystem• Food Web: A food web shows many paths of how energy moves through an ecosystem. A food web is made up of many different food chains.
  19. 19. FOOD CHAIN
  20. 20. FOODWEB
  21. 21. Primary productivity• Primary productivity is the rate of energy capture by producers.= the amount of new biomass of producers, per unit time and space
  22. 22. • Gross primary production (GPP) = total amount of energy captured• Net primary production (NPP) = GPP - respiration• Net primary production is thus the amount of energy stored by the producers and potentially available to consumers and decomposers.
  23. 23. • Secondary productivity is the rate of production of new biomass by consumers, i.e., the rate at which consumers convert organic material into new biomass of consumers.
  24. 24. CONCLUSION• Energy flow follows the second law of thermodynamics• Biomass decreases with increasing trophic level• Ecological efficiency – typically 10%