[BIO 1306] Ch54_Lecture

[BIO 1306] Ch54_Lecture - 54 Population Ecology 54...

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54 Population Ecology
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54 Population Ecology 54.1 How Do Ecologists Study Populations? 54.2 How Do Ecological Conditions Affect Life Histories? 54.3 What Factors Influence Population Densities? 54.4 How Do Spatially Variable Environments Influence Population Dynamics? 54.5 How Can We Manage Populations?
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54.1 How Do Ecologists Study Populations? A population consists of all the individuals of a species in a given area. Population structure describes the age distribution of individuals, and how those individuals are spread over the environment.
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54.1 How Do Ecologists Study Populations? The number of individuals per unit area or volume is the population density . Density has strong influence over how individuals react with one another and with populations of other species.
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54.1 How Do Ecologists Study Populations? Population structure changes over time due to demographic events : births, deaths, immigration, and emigration. These events create population dynamics . Study of these events is called demography .
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54.1 How Do Ecologists Study Populations? Population ecologists measure number and density of individuals, rates of demographic events, and locations of individuals. Individuals are often tagged or marked in some way to facilitate research. Tracking devices are also used. They may provide additional physiological and environmental data.
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Figure 54.1 By Their Marks You May Know Them
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54.1 How Do Ecologists Study Populations? Molecular markers are also used. Hydrogen isotopes have been used to determine where American redstarts molt during their migrations. Hydrogen isotopes in feathers reflect the latitude at which the feathers grew, because there is a strong latitudinal gradient of these isotopes in precipitation.
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Figure 54.2 Hydrogen Isotopes Tell Where Migratory American Redstarts Molted Their Feathers
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54.1 How Do Ecologists Study Populations? Population density of terrestrial animals is usually measured per unit area; for aquatic animals number per unit volume is used. Sometimes total mass of individuals or percentage of ground covered is used for density.
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54.1 How Do Ecologists Study Populations? Counting every individual in a population is often not possible. Ecologists use statistical methods to estimate population size from representative samples. For sedentary organisms, individuals in representative habitats can be counted, and the numbers extrapolated to the whole ecosystem.
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54.1 How Do Ecologists Study Populations? Estimating numbers of mobile animals involves capture and marking of some individuals, then capturing another sample of individuals. Proportion of marked individuals in the new sample is used to estimate population size: N n n m 1 2 2 =
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54.1 How Do Ecologists Study Populations? Estimates of population size using this
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This note was uploaded on 04/08/2008 for the course BIO 1306 taught by Professor Adair,tamarah during the Spring '08 term at Baylor.

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[BIO 1306] Ch54_Lecture - 54 Population Ecology 54...

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