2.1 Energy Flow in Ecosystems

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					        2.1 Energy Flow in Ecosystems
• Biomass is the total mass of all living things in a
  given area. (measured in g/m2 or kg/m2)

• Organisms interact with the ecosystem by:
    1. Obtaining food from the ecosystem
    2. Contributing energy to the ecosystem
       Energy Flow in Ecosystems
– Plants are called producers because they make
  carbohydrates during
  CO2 + H2O + sunlight  C6H12O6 + O2

– Consumers get their energy by feeding on
  producers or other consumers.
- Decomposers break-down wastes &
  dead organisms, through the process of
Energy Flow & Energy Loss in Ecosystems

• Methods to represent energy moving through ecosystems.
  – Food chains: show the flow of energy in an ecosystem.
  – Food webs: represent interconnected food chains.
    They model the feeding relationships in an ecosystem
  – Food pyramids: show the changes in available energy
    from one trophic level to another in a food chain.
    They’re also called ecological pyramids
                  Food Chains
• Each step is a trophic level
                           Terrestrial & aquatic food
  – Producers                        chains
    = 1st trophic level
  – Primary consumers
    = 2nd trophic level
  – Secondary consumers
    = 3rd trophic level
  – Tertiary consumers
    = 4th trophic level
• Consumers in a food chain can be classified as:
  1. Detrivores (decomposers) - obtain energy & nutrients
     from dead organisms & waste matter.
      they have their own, separate food chains & they
        feed on every trophic level.
                                                  This dung
      Eg. small insects, earthworms, bacteria    beetle is a
        & fungi                                   detrivore.

   2. Herbivores - primary consumers
       eat plants (producers) only
       Ex. Horse eating hay
3. Carnivores - secondary or tertiary consumers
    Secondary consumers eat non-producers (herbivores)
     • Eg. Frog eating a grasshopper
    Tertiary consumers eat secondary
     • also called top predators, top
       carnivores or top consumers
     • Eg. Lions eating humans
4. Omnivores - consumers that eat both
     • plants & animals
     • Eg. include humans and bears
                       Food Webs
• Most organisms are part of
  many food chains.
  – Arrows in a food web
    represent the flow of energy
    and nutrients.
  – Following the arrows leads
    to the top carnivore(s).

                                   This food web represents a terrestrial
                                    ecosystem that could be found in
                                            British Columbia.
                    Food Pyramids
• Energy enters at the first tropic level (producers), where
  there is a large amount of biomass & therefore a lot of
• It takes large quantities of organisms in one tropic level to
  meet the energy needs of the next trophic level.
       • 80% - 90% of energy taken in by consumers is used in
         chemical reactions in the body, or is lost as heat energy.
The amount of life an ecosystem can sustain is based on
 the bottom level of the ecological pyramid, where
 producers capture energy from the sun.
• Lower trophic levels have much larger populations than
  upper levels.
• This shows the importance of maintaining large, biodiverse
  populations at the lowest levels of the food pyramid.

 Take the Section 2.1 Quiz

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