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Lecture 16

BIOL215 Lecture 16 Notes.pdf

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Biology (Sci)
BIOL 215
Neil Price

BIOL215 Lecture 16 Notes In general, Lotka and Volerra predicts coexistence of two species when, for both species, interspecific competition is weaker than intraspecific competition Lotka-Voltera provided a mathematical model based on the logistic equation: Logistic equations for species 1 and 2: Intraspecific (within species) competition is represented by K-N/K The assumption is that resources diminish as N increases because of intraspecific competition Obviously resources will also decrease with interspecific (between species) competition. Lotka-Voltera proposed: Where a (alpha) and b (beta) are competition coefficients Populations will stop growing when: As summary: N will fill the space when N = K and N will fill the space when N = K /a 1 1 1 2 2 1 The line of "Zero isocline" which is the limit to the growth of the population of species 1 that is imposed by the number of individuals of species 2 Competition can lead to one species winning and the second species going extinct Some competition interactions can lead to coexistence We can understand competitive interactions only by knowing the resources involved and the mechanisms by which species compete The outcome of competition will depend on environmental factor In the Galapagos finches, there's been an avoidance of competition to a large extent by evolving characters that have displaced food competition. So it was competition that has driven evolution Plant ecologists proposed a triangle. Phil Grind says that in plants, it's not K or r that allows you to understand the different types of plants, but that a plant will respond to three different axis based on the triangle: importance of competition, importance of stress (temperature, draught, cold - gradual change in environment), importance of disturbance (fire, hurricane, tsunami - more local scale and is not something that is continuous). Competition is one of the three most important axis that will explain species cohabitation Predation Predation is different from competition because in competition, we have two species and their relationship is mediated by abiotic resources. In predation, the relationship between the two species is direct, one species is a source of food for the other species Predator kills and consumes its prey. Dynamics of predator prey populations: Population cycles of predators and prey are well documented for a wide variety of animals living • at high latitudes: lemmings, voles, muskrats, red fox, Arctic fox, ruffe
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