Learn how to census a population of organisms too numerous to count.
Group Size: any size—large groups work well
Suggested Age: 10-12 and up
Time: 30 min + 20 min to follow-up with optional census of actual organisms
Consider…
- Site: a lawn that is at least 40 square meters
- Safety: No special concerns
- Prep: obtain a pound of small beans, estimate the number of beans, prepare a 10 cm X 10cm wire quadrat square for each participant, stake off a measured area (nails & string), data board and marker
Focus Question: How would you estimate how many individuals are in a very large population?
Learning outcomes:
- Devise and use the quadrat census technique to estimate the size of a population.
- Suggest and examine sources of error in using this technique.
Summary:
The students are given the task of determining the population size of a very large population of “bean bugs.” (This “population” may be composed of popcorn, lentils, or some similar sized seed that have been spread over an area of a lawn.) Upon realizing that it will be impossible to count every individual in the study area, they will suggest that some type of sampling technique would be more appropriate. Through a leader guided discussion, the students devise a method of sampling the area and extrapolating their findings to the whole study site. They compare their results to the actual number of “bean bugs” and discuss sources of error.
The students are given the task of determining the population size of a very large population of “bean bugs.” (This “population” may be composed of popcorn, lentils, or some similar sized seed that have been spread over an area of a lawn.) Upon realizing that it will be impossible to count every individual in the study area, they will suggest that some type of sampling technique would be more appropriate. Through a leader guided discussion, the students devise a method of sampling the area and extrapolating their findings to the whole study site. They compare their results to the actual number of “bean bugs” and discuss sources of error.
Extension:
In order for the students to understand the usefulness of this technique, have them estimate the population size of plants or animals in the study area. See the “Follow Through” section for ideas.
In order for the students to understand the usefulness of this technique, have them estimate the population size of plants or animals in the study area. See the “Follow Through” section for ideas.
Download the activity PDF file: BeanBugs.pdf
Click on a category for other similar activities.