10-6-09 - Biology 330 Class Notes 10/6/09 dH/dt = rH...

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Biology 330 – Class Notes – 10/6/09 dH/dt = rH – (rho)*(H)*(P) dP/dt = -d*P + (alpha)*(rho)*(H)*(P) Some predator-prey populations have this pattern? most do, o some are more stable ASSUMPTIONS: (DON’T HOLD TRUE) o Assume rho is constant o No density dependence (carrying capacity, K) Predator efficiency was possibly decreasing according to Holling, % of prey population consumed (y-axis) vs. Prey density This is a type II functional response * There is always some handling time for capturing prey. Handling time increases with increasing prey density * Overhead tim increases with increasing prey density THRESHOLD OF SECURITY: When prey are very scarce, prey are abundant. The cost of search for this quantity of prey is very high, and thus these prey are left alone. They reproduce. As prey population increases, THE PREDATOR POPULATION Predators will search for prey once the prey get past the threshold of security We The cost of the search is greater than the benefit of eating the prey item The event of finding the prey below the threshold of security is random (not intentional) because the cost of search is too high Two isokynes for measuring density dependence
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Predator isocline number of prey needed to keep predator population stable (dH/dT = 0) some number of prey needed to keep the predator population constant Prey isocline number of predators needed to keep prey population stable (dP/dt = 0) Any number above the prey or predator population Anything left of the predator isocline means the Every predator and prey have a unique interaction Rabits feeding on strawberries have a different predator prey coupling than rabbits feeding on blackberries The two predator/prey isoclines
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10-6-09 - Biology 330 Class Notes 10/6/09 dH/dt = rH...

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