INTRODUCTORY ECOLOGY BIO 325
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This 1 page Class Notes was uploaded by Retta Mayert on Friday October 23, 2015. The Class Notes belongs to BIO 325 at University of Kentucky taught by P. Crowley in Fall. Since its upload, it has received 13 views. For similar materials see /class/228202/bio-325-university-of-kentucky in Biology at University of Kentucky.
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Date Created: 10/23/15
Trophic Cascade COMPARISON WITH KEYSTONE SPECIES CONCEPT Both describe effects of consumers on consumed Trophic cascades are focused on ecosystemlevel effects of high trophic levels on lower ones whereas keystone species are consumers that strongly in uence species diversity Trophic cascades and keystone species are usually used to address different issues and levels so they are rarely used together A keystone species might contribute to a trophic cascade and thereby in uence species diversity as well as overall abundance and productivity of lower trophic levels GENERAL FEATURES Top predators suppress the next level down freeing the one below that which then suppresses its prey and so oniresulting in high abundance at every other level from the top down So trophic cascades are associated with topdown control in which even primary productivity may be strongly in uenced by the top level Most often demonstrated in aquatic systems though migrating herds of grazing mammals can provide a twolevel terrestrial example Stable Isotope Analysis The abundance ratio of the heavier to the lighter stable isotope of certain elements in tissue may be indicative of trophic level photosynthetic pathway and other ecosystem features Tissue samples are bombarded with electrons in a mass spectrometer which causes them to ionize resulting in characteristic charge and behavior Diets trophic status and such of longdead but incompletely decomposed organisms can sometimes be determined by stable isotope analysis Ratio quot J Isotope Ratio Low Moderate High 13C 12C C3 plants C4 plants plankton 15N 14N C3 plants C4 plants Plankton low trophic levels high trophic levels 34S 328 C4 plants C3 plants Plankton