Predator-prey model –Generalizing the Lotka-Volterra rules
Look at the figure! Describe the temporal interdependencies between the populations (which population
increases first, which declines or even collapses first, how do the fluctuations run, are there any cyclic
regularities?)
1. On the basis of your findings try to fill in the text with appropriate key terms.
Lotka-Volterra (L.-V.) equations:
first L-V equation - The mean values of both populations _____________________________ periodically.
The maxima and the minima of the _____________________________ population follow the
corresponding values of the ____________________ population.
second L-V equation – Both populations fluctuate around a ____________________________ that
remains constant over long periods of time provided that environmental conditions do not change.
third L-V equation – If, due to some reason (e.g. catastrophes, intoxication ...), both populations are
strongly decreased, first the ______________ population recovers then the ________________
population follows.
2. Read p. 26 and 27, discuss under which circumstances the Lotka-Volterra rules are applicable?
lsg: Lotka- und Volterra-Regeln auf einen Blick:
1.
2.
3.
periodische Schwankung der Populationen – periodic fluctuations
Konstanz der Mittelwerte – constant mean values / average values
schnelleres Wachstum der Beutepopulation – quicker and higher growth rate of prey population
Welche Kritik wird gegen die Lotka-Volterra-Regeln vorgebracht?
Unter anderem folgende Kritik wird üblicherweise vorgebracht:
Räuber besitzen normalerweise mehr als nur ein Beutetier (können also auf eine andere Beute
ausweichen, wenn ein Beutetier knapp wird)
Zu- und Abwanderungen von Tieren werden nicht berücksichtigt.
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Doesnʼt consider competition among prey or predators:
Prey population may grow infinitely without any resource limits (the rabbits never run out of food).
excloses Carrying capacity, assumes exponential growth
Predators have no saturation: Their consumption rate is unlimited (the lynxes never get full).
only considers two interacting species, usually predators possess more than one prey (if the main
prey becomes scarce they can
does not consider immigration or emigration