Ecosystems and energy_flow


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Ecosystems and energy_flow

  2. 2. Ecosystem <ul><li>A community and its physical environment </li></ul><ul><li>Made up of two essential components: </li></ul><ul><ul><li>Abiotic factors </li></ul></ul><ul><ul><li>Biotic factors </li></ul></ul>
  3. 3. Abiotic factors <ul><li>The non-living components of an ecosystem </li></ul><ul><li>Consists of the elements which may be found in the environment </li></ul><ul><li>Abiotic factors may be: </li></ul><ul><ul><li>Physical </li></ul></ul><ul><ul><li>Chemical </li></ul></ul>
  4. 4. Physical factors <ul><li>Sunlight and shade </li></ul><ul><li>Temperature and wind </li></ul><ul><li>Amount of precipitation </li></ul><ul><li>Altitude and latitude </li></ul><ul><li>Nature of soil </li></ul>
  5. 5. Chemical factors <ul><li>Salinity of water </li></ul><ul><li>Level of dissolved O 2 and other gases </li></ul><ul><li>Level of plant nutrients </li></ul><ul><li>pH of soil and water </li></ul><ul><li>Level of natural or artificial toxic substances </li></ul>
  6. 6. Biotic factors <ul><li>The organisms in an ecosystem are either: </li></ul><ul><ul><li>Autotrophs </li></ul></ul><ul><ul><li>Heterotrophs </li></ul></ul><ul><li>Autotrophic organisms may be photoautotrophic or chemoautotrophic. </li></ul><ul><li>The heterotrophs include humans, animals and microorganisms. </li></ul>
  7. 7. Autotrophs <ul><li>Photoautotrophs possess chlorophyll and carry on photosynthesis. </li></ul><ul><li>Chemoautotrophs are bacteria that obtain energy from the oxidation of inorganic compounds such as ammonia, nitrites and sulfides. </li></ul>
  8. 8. Heterotrophs <ul><li>Heterotrophic organisms need a source of pre-formed nutrients and consume tissues of other organisms. </li></ul><ul><li>Consumers are classified according to the type of food they eat. </li></ul>
  9. 9. Types of Consumers <ul><li>Herbivores are animals that feed directly on green plants. </li></ul><ul><li>Carnivores are animals that eat other animals. </li></ul><ul><li>Omnivores feed on both plants and animals. </li></ul>
  10. 10. Types of Consumers <ul><li>Decomposers are fungi and bacteria that extract energy from dead matter, including waste and return nutrients back to the soil. </li></ul><ul><li>Scavengers are animals that feed on dead matter. </li></ul>
  11. 11. Food Chain <ul><li>Artificial devices that illustrate how energy and nutrients move from one organism to another though the ecosystem </li></ul><ul><li>Shows transfer of energy from one trophic level to another </li></ul>
  12. 12. Trophic levels <ul><li>A trophic level includes a group of organisms that obtain food in a similar manner. </li></ul><ul><ul><li>Producers </li></ul></ul><ul><ul><li>Primary consumers </li></ul></ul><ul><ul><li>Secondary consumers </li></ul></ul><ul><ul><li>Tertiary consumers </li></ul></ul><ul><ul><li>Quaternary consumers </li></ul></ul>
  13. 13. Food Chain
  14. 14. Food Webs: Who Eats Whom?
  15. 15. Food Web <ul><li>A complex network of interconnected food chains </li></ul><ul><li>The feeding relationship that actually exists in nature </li></ul><ul><li>May be: </li></ul><ul><ul><li>Grazing food web </li></ul></ul><ul><ul><li>Detrital food web </li></ul></ul>
  16. 16. Energy Flow <ul><li>Ecosystems are dependent upon solar energy flow and finite pools of nutrients. </li></ul><ul><li>The primary source of energy for ecosystems is sunlight. </li></ul><ul><li>All energy content of organic matter is eventually lost to the environment as heat. </li></ul>
  17. 17. Laws of Thermodynamics <ul><li>Energy can neither be created nor destroyed, but can be transformed into different forms. </li></ul><ul><li>When energy is transformed from one form to another, there is always some loss of energy from the system, usually as low grade heat. </li></ul>
  18. 18. 10% Law of Energy Transfer <ul><li>In general, about 10% of energy at a particular trophic level is incorporated into the next trophic level. </li></ul><ul><li>This rapid loss loss of energy explains why a food chain rarely has five links. </li></ul>
  19. 19. Energy Flow <ul><li>Energy enters ecosystems from an external source. What is it? </li></ul><ul><li>Energy flows linearly and exits an ecosystem through ___________. </li></ul><ul><li>What happens to the amount of energy as it travels through an ecosystem? </li></ul>
  20. 20. Ecological Pyramids <ul><li>Graphic representations of the relative energy amounts at each trophic level. </li></ul><ul><li>3 Types of Pyramids </li></ul><ul><li>1. Pyramid of Energy </li></ul><ul><li>2. Pyramid of Biomass </li></ul><ul><li>3. Pyramid of Numbers </li></ul>
  21. 21. Pyramid of Energy <ul><li>Energy content of each trophic level </li></ul><ul><li>Unit of energy = Kilocalories/meter 2 /year </li></ul><ul><li>Pyramid has large base and gets significantly smaller at each level. </li></ul><ul><li>Organisms use energy for work and respiration, so less energy is available to each successive trophic level . </li></ul>
  22. 22. Pyramid of Energy <ul><li>The figures represent the amount of energy at each trophic level expressed in kcal/m2/yr . </li></ul>
  23. 23. Pyramid of Biomass <ul><li>Biomass is a quantitative estimate of the total mass (amount) of living material…or </li></ul><ul><li>… the amount of fixed energy at a given time . </li></ul><ul><li>Measuring biomass: total volume, dry weight, or live weight </li></ul><ul><li>A 90% reduction occurs between each trophic level </li></ul>
  24. 24. Pyramid of Biomass <ul><li>Biomass also diminishes with the distance along the food chain from the autotrophs which make the organic molecules in the first place. </li></ul>
  25. 25. Pyramid of Numbers <ul><li>Illustrates number of organisms at each trophic level </li></ul><ul><li>Most pyramids show that there are many more individuals at the lower trophic levels. For example: the number of herbivores on the African plains (zebra, wildebeests) is far greater than the number of carnivores (lions). </li></ul><ul><li>BUT some number pyramids can be inverted. </li></ul>
  26. 26. Pyramid of Numbers <ul><li>Small animals are more numerous than larger ones. </li></ul><ul><li>If the size of the individuals at a given trophic level is small, their numbers can be large and vice versa. </li></ul>
  27. 27. Write the trophic level that each organism belongs to in this food web.