2005_campbl52

2005_campbl52 - 1 Chapter 52: Population Ecology Population...

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Unformatted text preview: 1 Chapter 52: Population Ecology Population Characteristics Population ecology studies organisms from the point of view of the size and structure of their populations; both are properties of populations, not individuals Population ecology also is the study of interactions within populations (i.e., intraspecific interactions) Recall that populations are groups of interacting conspecifics (i.e., inter-mating individuals) We can characterize individual populations in terms of their Size (average vs. variation) Density (& impacts on size; density dependence) Patterns of Dispersion Demographics (age structure, sex ratios) Rates of growth (or decline) Limits on population growth Population Dynamics Addition of individuals to populations Removal of individuals from populations Clumped Dispersion of Population Clumped dispersion implies some sort of cohesive force, e.g., either individuals seek other individuals out, or individuals are limited in where then can reside Uniform Dispersion of Population Uniform dispersion implies some sort of antagonistic interaction, e.g., either individuals actively repel other individuals Random Dispersion of Population Random dispersion implies a minimum of interspecific interactions that impact where individuals reside 2 Why Different Types? Population Demographics Age Structure Sex Ratios Evolution will tend to maximize the representation in a population of those individuals who display those combinations of life history traits that maximize the number of surviving progeny they produce Life History The traits that affect an organisms schedule of reproduction and survival (from birth through reproduction to death) make up its life history. (p. 1156, Campbell & Reece, 2002) "In many cases there are trade-offs between survival and traits such as clutch size (number of offspring per reproductive episode), frequency of reproduction, and investment in parental care. The traits that affect an organism's schedule of reproduction and death make up its life history. In other words, the Darwinian goal is to maximize lifetime reproductive output , and this can be achieved by having babies more rapidly or living longer, or some combination of the two, as well as by varying many additional details having to do with survival and reproduction Age-Structure Pyramids Rectangle = Cohort = group of individuals of the same age Note sex ratios are not always 1:1 Survivorship Selection here is stronger earlier in life Later in life simply fewer individuals left for selection to act upon Idealized Survivorship curves 3 Idealized Survivorship curves Type II curves are a simple exponential decline with age Exponential declines are due to accidents and predation at rates that do not appreciably change as a function of age Idealized Survivorship curves Because individuals tend to die exponentially due to...
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This note was uploaded on 12/07/2011 for the course BIO 113 taught by Professor Staff during the Fall '09 term at Rutgers.

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2005_campbl52 - 1 Chapter 52: Population Ecology Population...

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