UNI101Y1 Study Guide - Trophic Cascade
16 Feb 2013
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Increased productivity tends to increase the density of all higher trophic levels. Consumers could depress the size of the trophic level immediately below them and bump up the pop. two levels below. Bio120h lisa zhao 2011 | page 5. Trophic cascades caused by predators in food webs appear to be pervasive in communities, but their effects may even reach across diff. ecosystems. Fish prey on insects (ex. aquatic larvae of dragonflies) Ponds containing fish have less dragonfly larvae larvae that survive become dragonflies and prey on other flying insects. Dragonflies prey on pollinators (bees, flies, butterflies) Hypothesis: flowers near ponds w/o fish would receive fewer pollinator visits than those near ponds w/ fish. Since plants have been shown to set a normal # of seeds even when the amount of pollen they receive is reduced, they tested for pollen limitation by adding pollen to the st. john"s wort. Growing close to fish-free: pollen addition significantly improved seed set.
