# sg3ECO - 3 Chapter 52 overview 52.1 51.2 52.5...

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3) Chapter 52 overview, 52.1, 51.2, 52.5, 51.6 (1136-1143, 1148-1156) A. Distinguish between population density and dispersion . Describe how each is a dynamic, and not static, characteristic. Immigration emmigtation patterns of dispersion B, Define demography . Describe several ways of modeling demographic information. life table cohort survivorship curve reproductive table C. Describe the variability in reproductive patterns using three examples. D. Discuss how density-independent and density dependent factors limit population size. Give examples of these factors. F. Describe the significance of information found by examining age structure (see fig. 52.25) fecundity , mortality , life expectancy and sex ratio. Relate to life tables and survivorship curves A. . Every population has a specific size and specific geographical boundaries. The density of a population is measured as the number of individuals per unit area or volume. The dispersion of a population is the pattern of spacing among individuals within the geographic boundaries. . Measuring density of populations is a difficult task. We can count individuals, but we usually estimate population numbers. It is almost always impractical to count all individuals in a population. Instead, ecologists use a variety of sampling techniques to estimate densities and total population sizes. 0 For example, they might count the number of individuals in a series of randomly located plots, calculate the average density in the samples, and extrapolate to estimate the population size in the entire area. Such estimates are accurate when there are many sample plots and a homogeneous habitat. A sampling technique that researchers commonly use to estimate wildlife populations is the mark-recapture method. 0 Individuals are trapped and captured, marked with a tag, recorded, and then released. 1 After a period of time has elapsed, traps are set again, and individuals are captured and identified. 2 The second capture yields both marked and unmarked individuals. 3 From these data, researchers estimate the total number of individuals in the population. 4 The mark-recapture method assumes that each marked individual has the same probability of being trapped as each unmarked individual. 5 This may not be a safe assumption, as trapped individuals may be more or less likely to be trapped a second time. . Density results from dynamic interplay between processes that add individuals to a population and those that remove individuals from it. Additions to a population occur through birth (including all forms of reproduction) and immigration (the influx of new individuals from other areas). The factors that remove individuals from a population are death (mortality) and emigration (the movement of individuals out of a population).

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sg3ECO - 3 Chapter 52 overview 52.1 51.2 52.5...

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