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Unformatted text preview: Population Ecology o The study of the distribution and abundance of a population of a single species o Population- interacting group of individuals of the same species o Distribution- spatial arrangement of individuals with in a population o Abundance- the number of individuals per area (or volume) with in a population Can be static (at one point in time) or dynamic (change over time) o Ways to look at abundance: Increased: &#2; Unchanged: &#2; Decreased: Questions come in about how a population grows and reproduces: : Continuous: Discrete: o Ways to look at distribution: Clumped or contiguous: Regular or overdispersed: Random: Individuals may be antagonistic toward each other. How to Measure Distribution and Abundance o Abundance: Quadrat: a fixed area of known size; count individuals in the area Size of quadrat depends on what is being measured Take multiple sub-samples of a population to accurately estimate the size How to determine how many sample are needed: Statistics: Population- includes every individual from a given area Sample- study/test/manipulate a portion of a population and make inferences about the whole Look at the variance around the mean (standard error, standard deviation, etc.) The mean represents out best guess or inference about a population To get an estimate of what your sample size needs to be, go out and get a preliminary sample and see what the variance looks like However the optimal sample size may be huge Constrained by $, time effort, etc. Sample as large as possible with in your means It is possible for the population to change between the time the preliminary sample is taken and the time actual samples are taken Randomization of samples: For quadrats: On an oyster reef: overlay a grid and assign coordinates Use a computer, dice, etc. to randomly select squares Could possible lead to "clumping" of sampling locations Stratify: divide area into different sections and take random samples from the section Ex: high marsh vs. low marsh, age May be hard to recognize the different strata Clustering: a group of individuals that somehow influence each other Need to consider this when using a quadrat Transect: A straight line often set up along a gradient (ex. High marsh to low marsh) Take random samples from distances along line Regular intervals- best for detecting gradients Can be combined with use of a quadrat Point sampling: Often done on reefs modified quadrat- only count individuals that are at a single...
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- Spring '08