Chapter 55

Chapter 55 - Chapter 55 Population Ecology 55.1 How do...

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Chapter 55: Population Ecology 55.1 – How do ecologists study populations? o Ecology is studied at different levels, but the most basal level is organismal ecology o Populations are groups of organisms of the same species in the same area at the same time o Population dynamics involves the patterns and processes of changes in populations o Population density is the number of individuals per unit area o Demography is the number of individuals of each age and sex class in the population o Population size is increased by immigration and natality o Population size is decreased by emigration and fatality o Some populations are small enough to be counted by a full census, but most population densities must be inferred from samples o Ecologists measure them density per unit area of an area and generalize to estimate a population size o Individuals of sedentary species may be counted in areas called quadrats, or counted along a linear transect where any individual that touches the line is counted o By repeating these methods, ecologists can get a good estimate of the number of species in an area o The count mobile organisms, ecologists use the mark-recapture method, where the capture a group of individuals, set them free, and then recapture another sample from the same population and see how many of the individuals were captured twice. o This can be sued as a statistical method to estimate a population size (pg 1169 for formula and practical use) o A populations age structure is important to know because individuals within a population may differ significantly in their potential reproductive output o Dispersion refers to the distribution of individuals in a space within the population Determines patterns of interaction and affects population growth o The main dispersion patterns Clumped – when the presence of one individual at any point in space increases the probability of others being at that point (aphids cluster to break wind)
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Regular – occurs when the presence of one individual at any point in space reduces the probability of others being near that point (competition for food)
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This note was uploaded on 09/08/2011 for the course LS 1 taught by Professor Thomas during the Summer '05 term at UCLA.

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Chapter 55 - Chapter 55 Population Ecology 55.1 How do...

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