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Tritrophicmurray - TRITROPHIC INTERACTIONS READINGS FREEMAN 2005 Chapter 53 Pages 1229-1242 TRITROPHIC INTERACTIONS Eating(trophic relationships

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TRITROPHIC INTERACTIONS READINGS: FREEMAN, 2005 Chapter 53 Pages 1229-1242
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TRITROPHIC INTERACTIONS Eating (trophic) relationships often link several species in a community through herbivory, predation and/or parasitism. When the links go across three eating (trophic) levels, they are called tritrophic interactions. Species that play an special role in trophic relations are called “keystone species”.
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A TRITROPHIC INTERACTION Hover flies sip nectar from flowers and in turn are eaten by a spiders. This is a version of: Predators eat herbivores, and herbivores eat plants.
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ANOTHER TRITROPHIC INTERACTION (I) Daphnia are herbivores on a unicellular algae and the prey of damsel flies. A decrease in algae would soon result in a decrease in Daphnia and later a decrease in damsel flies.
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TRITROPHIC INTERACTION (II) A sudden decrease in Daphnia would result in a decrease in damsel fly larvae and an increase in unicellular algae. A sudden increase in damsel fly larvae would result in a(n) _____ of Daphnia and a(n) _____ of unicellular algae.
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FOOD CHAIN (I) A trophic interaction that links three or more levels is called a food chain. Where the trophic levels are dynamically linked, any change in abundance of one population within the chain can result in changes in abundance of the other populations.
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FOOD CHAIN (II) All food chains begin with producers [green plants, green algae and blue- green algae (cyanobacteria)]. Herbivores are known as primary consumers. Predators are known as secondary or higher level consumers.
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PREDICTED DYNAMICS OF TRITROPHIC INTERACTIONS (I) Where eating relations exert control on the abundance of populations within a food chain, a change in the abundance of one population can have an influence on the other populations. A change in abundance of producers will first change the abundance of primary consumers and later the abundance of secondary consumers.
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PREDICTED DYNAMICS OF TRITROPHIC INTERACTIONS (II) A change in abundance of secondary consumers will first change the abundance of primary consumers and later the abundance of producers. A change in abundance of primary consumers will change the abundance of one or both of the other immediate trophic levels and the timing of change is difficult to predict (depends on life history characteristics, etc.).
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WILLOW-HARE-LYNX Willow is a primary food of artic hare in the winter when food is scarce. Although evidence suggests that lynx control hare cycles, the hare population is subject to both top down and bottom up control. The interaction of food and predation has a strong influence on hare abundance.
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REVISITED (I) There is no strong evidence that wolves control moose populations on Isle Royal. There is good evidence
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This note was uploaded on 04/07/2008 for the course BIOS 101 taught by Professor Molumby during the Spring '08 term at Ill. Chicago.

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Tritrophicmurray - TRITROPHIC INTERACTIONS READINGS FREEMAN 2005 Chapter 53 Pages 1229-1242 TRITROPHIC INTERACTIONS Eating(trophic relationships

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