Materials Included In Kit

Additional Materials Required

Safety Precautions

Follow all normal classroom and field activity guidelines.

Disposal

The sampling square should be saved for further use.

Teacher Tips

• The sampling square contains an elastic band that runs throughout the construction of the device for easy assembly and storage.
• The sampling square is open at the elbows to allow the square to sink for underwater sampling studies. If desired, use an aquatic sampling net to collect organisms that are “kicked-up” from the sampling square area.
• Before taking students into the field, assess the location (e.g., schoolyard, field, empty lot, park) for an appropriate sampling area. In an urban setting, the grassy area between a sidewalk and street offers a surprisingly high amount of diversity.
• Record data for every group on the classroom blackboard or whiteboard for easy comparison.
• The Sampling Area Graph may be subdivided further for larger study areas.
• It is up to the instructor’s discretion on how in-depth the student classifications should be. The use of identification guides will greatly aid in the classification of the species found in the sampling area.
• The abundance of a certain plant or animal species may also be calculated by using the following formula:

  Abundance = number of a target organism/the total number of organisms

  An example is (the number of dandelions in an area)/(the total number of all plants in that area).
• A transect line may also be set up and data recorded if the terrain and time allows.
• If access to a sampling area outdoors is limited, this activity may be done in the classroom with “artificial” items (e.g., coins, bingo chips). Students may than extrapolate the population data from the various items into a larger given area.
• One sampling square is included in this kit. A classroom set of eight sampling squares is also available (Flinn Catalog AP6834).

Further Extensions

• Students may wish to compare two different sampling habitats and compare and contrast the similarities and differences between the two.
• The biomass of a plot may also be determined. Students should use clippers to cut off the above-ground vegetation in their sampling area and place these clippings in a collection bag. The clippings should be air dried for two days. Samples may also be placed in an oven (100 °C or lower) until the weight remains constant, if desired. Calculate the final biomass by weighing the dried clippings. Convert the final biomass to g/m².

Answers to Questions

1. What types of organisms were found in your sampling areas?

   Answers will vary.

2. Were species found in certain sampling areas and not others? Give possible reasons why or why not.

   Answers will vary. Answers may include that pollution, predation, or lack of habitat caused variations on organism locations.

3. Were your group's average species density values accurate representations of the entire study area? What about the entire classroom’s average species density values?

   Answers will vary. The general consensus should be that the entire class's average species densities should be more accurate than the individual group's densities.

4. What type of ecological sampling did your class perform—random, systematic or stratified?

   Random or stratified sampling should have been used with the sampling square.

5. What could be done to obtain a better average species density value?

   Answers may include—more samples could have been taken or larger areas could have been examined.

Introduction

What types of organisms are located in your local fields and streams? What are the populations of these organisms? Use a sampling square to find out!

Concepts

• Population density
• Sampling methods
• Habitats

Background

What types of organisms are in a particular habitat? It would be impossible to determine the overall number and types of species in a large area by actually counting each and every organism. These populations can be determined by simply taking a number of small samples from a certain habitat and extrapolating the data.

The most common unit used in ecological population sampling is a 1 m² quadrat. A quadrat is a set sample area where organisms within that area are counted. The purpose of using a quadrat is to enable comparable samples to be obtained from areas of consistent size and shape. Square quadrats are the easiest to use and give data that can be graphed and readily studied. The area of sample quadrat or sampling square used in this activity is 0.25 m².

There are three main types of ecological sampling: random sampling, systematic sampling and stratified sampling. Random sampling is carried out when the area of study is fairly uniform or very large. When using random sampling a large number of samples are usually taken from different areas within the habitat. One of the problems with random samples is that they may not cover all areas of a habitat equally. This is where stratified sampling comes into play. Stratified sampling is used to take into account drastically different areas within a habitat. For example, if a habitat contains 100 m² of grassland and 25 m² of swamp 75% of the samplings should be from the grassland and 25% should be from the swamp. This provides a better overall count of the organisms in that area. Systematic sampling is when samples are taken at fixed intervals, usually along a line. This normally involves doing line transects, where a sampling line is set up across areas having clear environmental gradients. A transect line may be used to show the changes of a species from a grassland area to a woodland area or another area where there is some kind of continuous variation along a line. Only the organisms that actually touch the transect line are recorded.

Further information about ecological sampling techniques and population studies may be found in a general ecology textbook.

Experiment Overview

In this activity, a 0.25 m² sampling square will be used to determine population density of a given area.

Materials

Safety Precautions

Follow all normal classroom and field activity guidelines.

Procedure

Preparation

1. With the instructor’s help, determine an overall area or habitat that is to be studied.
2. Draw a detailed map of this sample area on the Sampling Area Graph.
3. The sampling area on the Sampling Area Graph should be drawn to scale.

1. Obtain an assembled sampling square.
2. Determine the location to be sampled from the Sampling Area Graph. Mark this area as Sampling Area 1 on the Sampling Area Graph.
3. Lay the sampling square on this location.
4. Classify and count the number of target organisms (e.g., plants, insects) in this sampling location within the 0.25 m² area of the sampling square.
5. Convert the count of organisms to 1 m² by multiplying the 0.25 m² value by 4. Record all information on the Sampling Square Observation Sheet
6. Choose two additional sampling locations within the sampling area.
7. Repeat steps 3–5 for each additional location and record all information on the Sampling Square Observation Sheet.
8. Determine the average density for each of the species found by your group. Do this by adding the results of each species for each of the sampling plots and divide by the number of overall plots (see Equation 1). Record the average species density values as (number of species)/m² in the Sampling Square Observation Sheet.
   {12681_Procedure_Equation_1}
9. Repeat step 8 with the data from the plots gathered by every student group in the class.
10. Record all information on the Sampling Square Observation Sheet.
11. Determine the number of target organisms found in a 1 m² sampling location.
12. After all calculations have been made, answer the post-activity questions.

Student Worksheet PDF

12681_Student1.pdf