Sampling strategy for non-motile Organisms
This page explains how you can study an ecosystem using sampling techniques. It provides video explanations and a task to try and apply the thinking.
I designed this activity when my fieldwork was cancelled, and I was unable to take students out to show them these techniques. I don't think these should replace fieldwork, but they can certainly help students be more prepared for going out into the field. In the future, I will have students watch these videos before we do fieldwork.
Following up from this activity, we will look at an application in an exam of these techniques. Applying Sampling Strategies Exam Questions.
Sampling techniques allow a representative sample of an ecosystem to be studied and conclusions to be drawn for the entire ecosystem. Sampling strategies help the ecologist to avoid bias. The two main strategies used are systematic or random sampling with either transects or quadrats or both. We then look at how to estimate the population size of non-motile (don't move) organisms, i.e. plants. This is explained theoretically on 2.5 Sampling Strategies and Measurements - "Where and How Many?" but on this page we see it more in practice with these videos. Finally there is a task for students to try and apply this information. Six different ecosystems are introduced and students are challenged to propose a question and a method to investigate that ecosystem.
Watch each of the videos about when to use transects or quadrats or both, then the methods of estimating plant populations: 1. Actual Counts, 2. Population Density, 3. Percentage Cover, and 4. Percentage Frequency, and take notes so that you are prepared to apply this information.
Your task is set in the final video, Investigating Ecosystems. Watch the video and then for each of the six ecosystems, decide what question you might ask of that ecosystem and describe your sampling strategy to answer that question.
You should produce a table with the six ecosystems, the question you would ask and the sampling strategy you would use.
Remember that for quadrats you need to sample a sufficient amount of the ecosystem (usually about 10%) and for transects, in this course, you are required to complete 3 parallel transects as a minimum with 15 points along the transect.