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  • 1. Biotic components 5th lecture
  • 2. Biotic com.Producers Consumers Decomposers
  • 3. ProducersProducers are able to manufacture their food fromsimple inorganic substances (e.g. CO2). Producers includegreen plants, algae and other photosynthetic protists, andsome bacteria.
  • 4. ConsumersConsumers are organisms that feed on autotrophs oron other heterotrophs to obtain their energy.•Includes: animals, heterotrophic protists, and somebacteria.
  • 5. DecomposersDecomposers are consumers that obtain theirnutrients from the breakdown of dead organicmatter. •They include fungi and soil bacteria.
  • 6. ConsumersHerbivores Carnivores Omnivores
  • 7. Living things are classified accordingto the way in which they obtain theirenergy: Producers (or autotrophs) Consumers (or heterotrophs)
  • 8. Trophic Structure 1Every ecosystem has a trophicstructure: a hierarchy of feedingrelationships which determines thepathways for energy flow and nutrientcycling.Species are assigned to trophic levelson the basis of their nutrition.Producers (P) occupy the first trophiclevel and directly or indirectly supportall other levels. Producers derive theirenergy from the sun in most cases.
  • 9. Trophic Structure 2 Producer (P)All organisms other than producers are consumers(C). ConsumerConsumers are ranked according to the trophic level (C1)they occupy. First order (or primary) consumers(herbivores), rely directly on producers for theirenergy. A special class of consumers, the detritivores, derive Consumer their energy from the detritus representing all (C2) trophic levels.Photosynthetic productivity (the amount of food Consumergenerated per unit time through photosynthesis) sets (C3)the limit for the energy budget of an ecosystem.
  • 10. Organization of Trophic LevelsTrophic structure can be described by trophic level or consumer level:
  • 11. Major Trophic LevelsTrophic Level Source of Energy Examples Green plants, photosynthetic Producers Solar energy protists and bacteria Grasshoppers, water fleas, Herbivores Producers antelope, termites Primary Wolves, spiders, Herbivores Carnivores some snakes, warblers Secondary Primary carnivores Killer whales, tuna, falcons Carnivores Humans, rats, opossums, Omnivores Several trophic levels bears, racoons, crabsDetritivores and Wastes and dead bodies Fungi, many bacteria, Decomposers of other organisms earthworms, vultures
  • 12. Trophic LevelsOrganisms can also be identified by the type of food theyconsume: Herbivores (Plants) {Deer} Carnivores (Meat) {Wolves} Omnivores (Plants/Meat) {Bears} Scavengers (Carcasses) {Crows} Detritivores (Debris) {Ants} Decomposers (All) {Bacteria}
  • 13. Food ChainsThe sequence of organisms, eachof which is a source of food for thenext, is called a food chain. Food chains commonly have four links but seldom more than six. In food chains the arrows go from food to feeder. Organisms whose food is obtained through the same number of links belong to the same trophic level.
  • 14. Food chain After lion dead
  • 15. Food WebsSome consumers (particularly ‘top’ carnivores andomnivores) may feed at several different trophic levels, andmany herbivores eat many plant species. For example, moose feed on grasses, birch, aspen, firs, and aquatic plants.The different food chains in an ecosystem therefore tend toform complex webs of feeding interactions called a foodweb.
  • 16. Food Webs
  • 17. Ecological Pyramids 1Trophic levels can be compared by determining the number,biomass, or energy content of individuals at each level.This information can be presented as an ecological pyramid.The base of each pyramid represents the producers and thesubsequent trophic levels are added on top in their ‘feedingsequence’.
  • 18. Ecological Pyramids 2Various types of pyramid are used to describedifferent aspects of an ecosystem’s trophicstructure: Pyramids of numbers: In which the size of each tier is proportional to the number of individuals present at each trophic level. Pyramids of biomass: Each tier represents the total dry weight of organisms at each trophic level. Pyramids of energy (production): The size of each tier is proportional to the production (e.g. in kJ) of each trophic level.
  • 19. Pyramid of numbers No.ofOrganisms C2 1 C1 6 Producers 10
  • 20. Pyramid of biomassBiomass C2 5 kg C1 10 kg Producers 20kg
  • 21. Pyramid of energy
  • 22. • In pyramids of biomass, dry weight is usually used as the measure of mass because the water content of organisms varies• Pyramids of energy (or production) are often very similar in appearance to pyramids of biomass.
  • 23. Thank you