Food chain: The sequence of organisms that provide food for one another

→ started by green plants because they are able to capture light energy from the sun

→ making green plants at the lowest trophic level

Food web: gives a more realistic picture of the feeding relations of the organisms in a habitat

Energy pyramid: A diagram that shows the amount of energy that moves from one feeding level to another in a food web

→ width of each layer in an energy pyramid is proportional to the amount of energy it represents- the higher up on the food chain it goes the smaller the layer becomes

• plants called producers because they produce organic compounds by photosynthesis

• every other organism other than plants gets its organic compound from its food making them heterotrophs or consumers

• every ecosystem has a hierarchy of feeding relationships that influences how nutrients and energy pass through it

  • arrows in a food chain always point in the direction in which the energy and nutrients flow

• detrivores and saprotrophs getting their nutrients from dead organisms play a vital role in returning inorganic nutrients to the abiotic environment

  SUMMARY OF A FOOD CHAIN:

  1. producer

  2. primary consumer

  3. secondary consumer

  4. tertiary consumer

     → organisms may change trophic levels depending on what they eat. for example, a fox can be a primary consumer if its just eating a crap apple, but it can be a secondary consumer when eating a woodmouse

     ENERGY LOSS IN A FOOD CHAIN

     1. not consumed

     ex. green plants store energy from photosynthesis but the antelope only eats parts of the grass so it does not consume all of the energy the grass has stored

     2. lost through death

     ex. not all of the plant is digested or absorbed so some passes out in feces. If the antelope dies the energy from its body is lost to the food chain

     3. cellular respiration

     ex. the antelope uses energy to move and keep its body temp constant, so some of the energy is lost to the environment as heat

     • ecosystems don’t contain more than four or five trophic levels because there isnt enough energy to support another level