This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
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:  Unchanged:  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 subsamples 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...
View
Full
Document
 Spring '08
 Walters
 Demography, Population Ecology, density dependence, high marsh

Click to edit the document details