ecology 8

odd number of trophic levels

green; plants resource limited; "bottom up" limitation

even number of trophic levels

barren; plants consumer limited; "top down" limitation

bottom up level

number of energy transfers from fixation of organic carbon to reach level

top down level

number of lower levels that are alternatively released and suppressed when this level is removed (plus one)

trophic level

functional grouping of organisms according to their primary food source

reasons food chain theory might not work

green stuff could be inedible, consumers are co-limited by
predators and food (or other
factors), omnivory blurs trophic levels, factors other than consumers or food limit populations

keystone species

a species that consumes and limits the population of another species that would otherwise dominate the system