BIOL 151 Final: Chapter 16 notes for final exams

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University of North Dakota
BIOL 151
Chris Felege

Population Ecology Introduction • A population is a group of individuals from the same species that live in the same area at the same time • Population ecology is the study of how and why the number of individuals in a populations changes over time • Most species identification guide show the range, or geographic distribution, of different species • Abiotic and biotic factors both determine range • Ranges are dynamic - in constant flux as abiotic and biotic factors change over time • The population density - the number of individuals per unit area- often varies throughout its range • An individuals arrangement within a population may be ◦ Random ◦ Clumped ◦ Uniform • A metapopultion is a population of populations connected by migration • The number of individuals present in a population depends on four processes: ◦ Birth ◦ Death ◦ Immigration ◦ Emigration • Demography is the study of factors such as these that determine the size and structure of populations through time • A life table summarizes the probability that an individual will survive and reproduce in any given time interval over the course of its lifetime • Survivorship is a key component of a life table ◦ The survivorship curve is a plot of the logarithm of the number of survivors versus age • Type I curve • Type II curve • Type III curve • Fecundity is also a key part of a life table ◦ Defined as the number of female offspring produced by each female in the population • Age-specific fecundity is the average number of female offspring produced by a female in a given age class - a group of individuals of a specific age • The per capita rate of increase is the difference between the birthrate and death rate per individual: ◦ R=b-d • When birthrates per individual are as high as possible and death rates per individual are as low as possible, r reaches a maximum value called the intrinsic rate of increase • Exponential population growth occurs when r does not change over time ◦ It does not depend on the number of individuals in the population • It is density independent • Carrying capacity is the maximum number of individuals in a population that can be supported in a particular habitat over a sustained period of time ◦ Not fixed • Population dynamics are the changes in populations through time Community Ecology Introduction • Abiological community consists of interacting species, usually living within a defined area • Fitness - the ability to survive and produce offspring • There are four general types of interactions among species in a community: 1. Commensalism occurs when one species benefits but the other species is unaffected (+/0) 2. Competition occurs when individuals use the same resources - resulting in lower fitness for both (-/-) 3. Consumption occurs when one organism eats or absorbs nutrients from another, increasing the consumer's fitness but decreasing the victim's fitness (+/-) 4. Mutualism occurs when two species interact in a way that confers fitness benefits to both (+/+) • Intraspecific competition occurs between members of the same species •
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