ehj351 lec_3 - 18/01/2011 INTERESTEDINTAKINGAFIELDCOURSE?

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18/01/2011 1 Types of resources; their interaction and effect on population growth EHJ 351 2011; Lecture 3 January 18 INTERESTED IN TAKING A FIELD COURSE? WANT TO PARTICIPATE IN A UNIQUE OPPORTUNITY WITH YOUR PEERS IN AN EXCITING LOCATION? Join us for EEB's Field Course Info Session 2011! When: Tuesday, January 18, 2011 @ 4:30 pm Where: RW117 (Ramsay Wright Zoological Laboratories, 25 Harbord St) This Info Session will include presentations from the instructors of EEB's field courses for 2011. Each instructor will tell you about the exciting experiences and opportunities available on their course, and you can ask them questions! There will also be information presented about the Ontario Universities Program in Field Biology (OUPFB), whereby you can receive credit for field courses taken through other universities. For information and application forms for both EEB and OUPFB field courses, please visit: www.eeb.utoronto.ca/undergraduate/field courses Finishing lecture 2 Logistic Equation dN dt rN 1 N K A more general version of the logistic 1, 0 dN N rN dt K     Theta logistic equation 0.2 0.4 0.6 0.8 1.0 0.2 0.4 0.6 0.8 1.0 per capita growth rate Population size relative to K θ = 4 θ = 1 (logistic) θ = 1/4 Problems with the applicability of logistic growth to humans 1. Increased population size has many potentially positive effects on birth and death rates in humans 2. Many effects have time lags—they take time to be fully effective 3. Age/size and spatial structure of populations not represented; different classes have different effects on and sensitivities to density e.g. p 0 is function of N 0 , N 1 , .... 4. many more BUT, IT IS TRUE THAT GROWTH EVENTUALLY STOPS IF POPULATION IS HIGH ENOUGH FOR LONG ENOUGH A set of entities are resources with respect to a set of consumers if: (1) The entities can be consumed by a consumer individual, where consumption means that they are at least temporarily transformed to an state that is unavailable to other consumer individuals. (2) Consumption has a positive effect on the fitness of the consumer individual. (3) Sufficient consumption has the potential to decrease resource abundance enough to decrease consumer per capita population growth
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18/01/2011 2 New lecture: Why study resources? Resources limit population growth; the ability to be reduced by consumption is part of the definition of a biological resource (the other part is that its greater abundance increases population growth) Studying consumer resource interactions automatically accounts for one major reason for the delay in the impact of higher densities on birth/death What keeps nonhuman populations from becoming huge?
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ehj351 lec_3 - 18/01/2011 INTERESTEDINTAKINGAFIELDCOURSE?

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