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Energy and the ecosystem IGCSE


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Energy and the ecosystem IGCSE

  1. 1. Energy and the ecosystem B M Subramanya Swamy M.Sc. B.Ed. CIE Co ordinator & Examination Officer Kanaan Global School Jakarta Indonesia
  2. 2. Overview of the topic 1.Energy flow •Producers/Consumers 2.Food chains and web •Food chains •Energy transfers •Food web 3. Ecological pyramids •Pyramid of numbers •Pyramid of bio mass 4.Nutrient cycle •Carbon cycle
  3. 3. • Ecology : Study of how organism interact with each other & with their environment • Environment – organism live • Environment – divided into abiotic & biotic factor • Abiotic factor-nonliving factor • E.g. edaphic factor, climatic factor & topographical factor • Biotic factor- living organism • E g producer consumer decomposer • Habitat – physical location in which an organism lives
  4. 4. Level of ecological organization • Earth – lump of rock with a thin outer layer of soil, water & air. • Organism occur near boundaries either between soil & air or water & air • Organism – studied at six different levels – individual,population,community ecosystem, biome & biosphere • Each species is made up of individual • Guases competitive exclusion principle states- two species cannot coexist unless there are significant difference in their ecologies. If 2 species attempt to occupy the same niche, they will compete with each other until one is eliminated • Niche – position of species occupied within its habitat. • Niche includes physical space its interaction with other organism & its effect on environment • Individual – same species occupying a constitute a population
  5. 5. • • Different population in an area interact with each other. These collectively form a community Community – named after an obvious feature of the environment – Pine forest community – Woodland community – Grassland community • Different species of a community together with their non living environment, constitute a ecosystem • Ecosystem consists of 4 basic element – Abiotic component – Biotic component – Energy & nutrient (support life in ecosystem) • Ecosystem are open unit & part of a biome • All the life are restricted to a rather narrow zone called the biosphere
  6. 6. Energy flow The main energy source on the earth is sun. Solar energy can be tapped by the plants to make food. Recently we are also able to tap this energy source using solar panels.
  7. 7. Producers / consumers • Green plants store solar energy in carbohydrates during photosynthesis. • They change solar energy into chemical energy to achieve this • They are producers (autotrophs): capable of producing their own food. • Consumers (heterotrophs) feed on producers as a source of food.
  8. 8. Some terms associated with energy flow Terms Definition Producer Autotrophs Produces its own food e.g. green plants Consumer Heterotrophs Feeds on producers e.g. animals and man Feeds on plants e.g. cattle Herbivore Carnivore Omnivore Feeds on animals e.g. lions Feeds on plants and animals e.g. crows
  9. 9. Trophic level: All the organisms that are the same number of food-chain steps from the primary source of energy Modified from: General Ecology, by David T. Krome
  10. 10. Foods chains and webs Food chains • Producers and consumers play different roles in the community. • These roles are termed as niches. • The different niches can be classified in various ways in the community. • When a herbivore eats a plant, and is then eaten by a carnivore, a chain of events from: based on feeding habits • The forms the food chain.
  11. 11. Classification of niches in the food chain Food chain Named Consumer level Tropic level Phytoplankton Producer Producer 1st trophic level Mussels Herbivore 1st order consumer 2nd trophic level Crab Small carnivore 2nd order consumer 3rd trophic level Man Larger carnivore 3rd order consumer 4th trophic level Bacteria Decomposer 4th order consumer 5th trophic level
  12. 12. Energy transfers • Energy flows in one direction along food chain. • Energy is transferred along the food chain. • At the next level, energy is lost..therefore energy supplied from level to level decreases. • The more levels in the food chain, the lesser the energy at the end of the chain. • Green plants capture only 1% of solar energy. • 10% of energy at every trophic level is converted into biomass.
  13. 13. Example of a Food Chain
  14. 14. Food Webs • All the food chains in an area make up the food web of the area.
  15. 15. Food web of a hot spring © 2003 John Wiley and Sons Publishers
  16. 16. Food web • In reality, predators feed on more than one type of prey. • When several different food chains can be strung together, it forms a food web. • A food web interconnects several food chains within an ecosystem. Ecological pyramids •A graphical representation of the energy, biomass or numbers of organisms at each trophic level. •Each trophic level forms a tier in the pyramid •They are called pyramids because of the shape of these graphs.
  17. 17. Pyramid of numbers and biomass Pyramid of numbers Pyramid of biomass The base has the largest number of organisms Represents the dry mass of all the organisms at that tropic level The number of organisms reduce as you reach the higher tiers of the pyramid The lengths of the bars estimates the relative biomass May be upright of inverted May be upright or inverted An example of a pyramid of numbers Owl Snakes Mice grass
  18. 18. Pyramid of numbers
  19. 19. Pyramid of Energy: • Shows the energy available at each trophic level. – The size of the blocks represents the proportion of productivity – Measured in Joules or Calories
  20. 20. Pyramid of Energy: • Most of the energy available to the community is in the 1st trophic level. • Only 10-20% of the energy is available to the next trophic level (≈ 90% lost)
  21. 21. Nutrient cycle • Nutrients in the environment exist in various forms. • Energy cannot be recycled, but the nutrients can • Carbon is repeatedly recycled within the environment Carbon cycle •Carbon dioxide occupies about 0.03% by volume of air. •This amount is sufficient for all plants that photosynthesis •CO2 is removed from the air by green plants. •It is replaced through respiration and by the combustion of fossil fuels.
  22. 22. CO2 CO2
  23. 23. Nitrogen cycle • Passage of nitrogen within an ecosystem • Nitrogen cycle is more complex biogeochemical cycle • Atmosphere contain 79% nitrogen gas but only few micro organism can tap this reservoir. • Nitrogen fixation – nitrogen fixing bacteria • Bacteria free-living or living in root nodules of leguminous plants • Bacteria converts atmospheric nitrogen to nitrates • Atmospheric nitrogen can also fixed by lightning
  24. 24. • Denitrifying bacteria converts nitrates to nitrogen gas – Bacteria are anaerobic – Process is known as denitrification • Photosynthetic organisms make use of nitrates to form amino acids & protein, which are in turn eaten by animals • Protein are broken down to amino acids in animals • Nitrogen in amino acids is excreted in the form of ammonia or urea • Decomposers breakdown protein molecules in dead animals and plants • Release nitrogen as ammonia or ammonium compounds- ammonification • E.g. putrefying bacteria • • Ammonia or ammonium compounds to nitrites & nitrites to nitrates Process is known as nitrification
  25. 25. N2 in Atmosphere N03- & NH3 N02-