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5.1 Communities


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IB Topic 5: Ecology

IB Topic 5: Ecology

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  • 1. 5.1: Communities Topic 5: Ecology & Evolution Miss Friedman
  • 2. 5.1.1: Definitions
    • Ecology
    • The study of the relationship between living organisms and between those organisms and their environment
    • Ecosystem
    • A community and its abiotic environment
    • Population
    • A group of organisms of the same species who live in the same area at the same time
  • 3. 5.1.1: Definitions
    • Community
    • Populations of different species in the same area which are interacting
    • Species
    • A group of organisms which can interbreed and produce fertile offspring
    • Habitat
    • Location within which a species normally lives
  • 4. 5.1.2: Autotrophs & heterotrophs Obtains organic molecules from other organisms consumer Heterotroph An organism that synthesises its organic molecules from simple inorganic molecules Producer Autotroph
  • 5. 5.1.3: Consumers, detritivores, saprophytes
    • Consumers
    • An organism that ingests other organic matter that is living or recently dead
    • Detritivores
    • An organism that ingests non-living organic matter
    • Saprophytes
    • An organism that lives on or in non-living organic matter, secreting digestive enzymes into and absorbing the products of digestion
  • 6. 5.1.4: Food chains
    • Food chains show a simple linear flow of “who eats who”
    • Therefore shows the energy flowing through the links in the chain
    • Questions to consider!
    • How is energy lost in the chain?
    • Why are big, dangerous predators so rare?
  • 7.  
  • 8. 5.1.5: Food webs
    • A diagram that shows how food chains are linked together into more complex feeding relationships
    • Advantages over food chain
    • Shows much more complex interactions between species within a community/ecosystem
    • More than one producer supports a community
    • A single producer is a food source for many primary consumers
    • A consumer might have a number of different food sources on the same/different trophic levels
    • A consumer can be an omnivore, feeding as a primary consumer but also as a consumer at higher tropic levels
  • 9.  
  • 10. 5.1.6: Trophic level
    • The tropic level of an organism defines the feeding relationship of that organism to other organisms in a food web
    Trophic level 4 Tertiary consumer heterotroph Trophic level 3 Secondary consumer Hetertroph Tropic level 2 Primary consumer Hetertroph Tropic level 1 Producer Autotraph
  • 11. 5.1.7: Determining tropic levels in food chains/webs
    • Assign tropic levels to the food web on the right!
  • 12. 5.1.8: Constructing a food web
    • Producers are usually shown at the bottom
    • Use full name of organisms
    • Arrows show the movement of matter & energy
  • 13. 5.1.9:Light & food chains
    • Sunlight is the source of energy for most communities, both aquatic and terrestrial
    • Very few communities deep in the ocean use geothermal energy
  • 14. 5.1.10: Energy flow in Food chain
    • a) Not all solar energy will come into contact with chlorophyll and will therefore not be trapped in the synthesis of organic compounds
    • b) Photosynthesis
    • c) Consumers feeding and passing on energy in the food
    • d) Loss of energy as heat from respiration
    • e) death and the consumption of dead organisms by detritivores. Or as food not assimilated because of incomplete digestion.
    • Energy Loss
    • loss of energy in undigested food which will then be used by saprophytes/ decomposers
    • loss of heat energy in the reactions of respiration
    • ultimately all energy will be lost has heat
  • 15. 5.1.11: Efficiency of energy transformations
    • When energy is changed from one form into another, it is never 100% efficient
    • Approximately only 10-20% of the energy on one trophic level will be assimilated at the next higher trophic level
  • 16. 5.1.12: Shape of energy pyramids
    • A pyramid of energy is a graphical representation of the amount of energy of each trophic level in a food chain
    • The units are kJ/m 2 /yr
    • The narrowing shape illustrates the gradual loss of energy processing along the links of a food chain to higher trophic levels
  • 17. 5.1.13: Energy and matter in ecosystems
    • Energy is NOT recycled through the ecosystem
    • Energy is constantly received from the sun and constantly radiates out in the form of light & heat
    • Matter IS recycled
    • The process of recycling nutrients requires energy
  • 18. 5.1.14: Decomposers
    • Two main groups are detritivores (e.g. earthworms, dung beetles) and saprotrophs (e.g. fungi, bacteria)
    • Decomposition is a complex process and serves many functions; formation of soil, recycling of nutrients, reduction of high energy carbon compounds
    • Organic molecules are oxidized to release nitrogen in the form of nitrate, nitrite, and ammonia
    • Oxidation of organic compounds provides energy for saprophyte but returns matter to abiotic environment