es_100_Lecture_13

es_100_Lecture_13 - TERM PAPER TOPICS DUE TODAY! Pass...

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Unformatted text preview: TERM PAPER TOPICS DUE TODAY! Pass papers to aisle. Include name, section, perm number. Lecture 13 Predator Prey Cycles Top down versus bottom up control I. Do predators cause population cycling in prey and vice versa ? Logistic growth equations can be generated for predator and prey Prey growth reduced as a function of predator consumption rate . Predator growth rate increases as a function of conversion efficiency and consumption rate . Equations can be manipulated to create population oscillations where predators drive prey. BUT DOES THIS HAPPEN IN REAL POPULATIONS? Rarely Classic predator/prey cycling: Rotifers and algae in lab culture Rotifers=predators. Algae = prey. Simple lab system. Controlled resources. Predators short lived with rapid numerical responses to prey Prey respond quickly when predators decline. predator Figure 7.18 Townsend Does predator cause prey to cycle ? Lynx = predators. Snowshoe hare = prey. More complex example from nature. Slower responding animals. Still looks like predator is controlling prey and vice versa. IN NATURE Food web of these animals = complex Arrows indicate who eats who Are hares actually controlled by the lynx? What are the other possibilities? Other predators? Or Food supply? Hare cycles driven by food hares overshoot WINTER food supply causing decline in birth rates and an increase in juvenile mortality (density dependent mortality)-then predation plays a stronger role when hares are at high density with low food supply Are hares actually controlled by the lynx? Winter food supply strongly affects juvenile growth and survivorship Starving juveniles are more subject to predation Lynx cycle follows their main prey Despite eating wide variety of species, lynx cycles are largely driven by hare numbers...
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This note was uploaded on 12/25/2009 for the course ENV S 100 taught by Professor Staff during the Fall '08 term at UCSB.

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es_100_Lecture_13 - TERM PAPER TOPICS DUE TODAY! Pass...

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