DesignEcologicalStudy - Designing an Ecological Study from...

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Biology 6C- Spring/Summer 2008 Designing an Ecological Study from G.W. Cox, General Ecology Laboratory Manual ! What kinds of questions do ecologists study? ! How can one identify an ecological topic for investigation? ! What steps do ecologists follow in testing hypotheses about ecological systems? Ecology can be defined as the study of ecological systems. A system is any set of components, living or nonliving, that are tied together by regular interactions. An ecological system is made up of one or more organ- isms, together with the nonliving environment with which they interact. Ecological systems exist at several different levels of organization. An ecological system can be a single organism and its surroundings, a population or set of interacting populations in a certain habitat, or the entire community together with the abiotic environment with which these species interact, a unit termed an ecosystem. Ecologists are interested both in the structure and function of ecological systems. Structure refers to measurable conditions of the system at one point in time. These include biotic attributes such as the body mass of an organism, the density of individuals in a population, the ratio of predator numbers to those of a prey species, or the biomass of all species that share some basic feature, such as photosynthesis. Structure also includes the physical and chemical conditions that prevail in the space occupied by organisms. Function refers to the processes that create structure at a given instant, and how these processes are affected as structure changes. Function includes, for example, the relationships that determine the growth rates of organisms, the rates of survival and reproduction of individuals in populations, the rates of predation by one species on another, and the intensity of other interactions, such as competition and mutualism. These processes determine the distribution and abundance of species, and thus the makeup of communities and ecosystems. Function also includes system-level processes, such as the cycling of nutrients and flow of energy among the components of an ecosystem. A major goal of modern ecology is to understand how ecological systems function, so that their behavior can be predicted, and so that they can be managed for long-term human benefit. To this end, ecologists seek to be rigorous in their techniques of investigation. What is the hypothesis-testing method? Most ecologists use the hypothesis-testing or hypothetico-deductiveapproach in their studies. This approach, based largely on the ideas of Karl Popper (1968), is the statement of explicit hypotheses about ecological relationships, followed by collection of data that lead to their acceptance or rejection. It views activities that cannot lead to rejection of certain hypotheses and the acceptance of others as wasted efforts, which do not advance ecological knowledge. The need for a rigorous hypothesis-testing approach has been stressed by many ecologists (Quinn and Dunham 1983, Connor and Simberloff 1986). The effort
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DesignEcologicalStudy - Designing an Ecological Study from...

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