Bottom Up and Top Down Control

• what does bottom up refer to?


  nutrients or food resources control the trophic levels above them
• what does top down refer to?

  predators or consumers control the trophic levels below them
• why is there a false dichotomy between bottom up and top down?

  they are equally important and efficient - they interact and combine
• which model combines top down and bottom up control?

  the PEG model
• what does the PEG model predict about bottom up control?

  there will be a positive correlation between all trophic levels
• what does the PEG model predict about top down control?

  there will be a negative correlation between adjacent trophic levels
• what is a trophic cascade?

  when a top down effect goes down more than one trophic level