The Transect Method
When engaging students in an investigation of a particular ecosystem we can facilitate them to understand the factors that characterize that ecosystem. These factors can be categorized into biotic (living things) and abiotic (non-living things).
Through questioning and/or journal writing we, as teachers, can get a sense of what students bring with them to school as far as their understanding of what an ecosystem is, which ones they are familiar with and what factors determine the differences between one and the other.
When the extent of the students conceptual understanding of ecosystems has been established, this information can help you, as the teacher, know how to tweak the investigative project.
It is impossible to count every living and non-living thing in an ecosystem. So a great method for finding out what things exist in an ecosystem is by establishing transects. A transect is a defined area in which sample population counts of plants and animals can be taken. The defined area has to be large enough to truly characterize the biotic and abiotic factors of the ecosystem. The size of a transect is determined by the biotic factors in the area chosen to investigate. If the area is in a grassland, where plants are plentiful and close together, you may choose a one-meter square in which to count all species of plants and animals. If the area is in a sparsely vegetated area such as a desert, you may choose a 10-meter or even a 100-meter square in which to count your populations.
Transects can be established in many ways. Students can measure off a square in a pre-determined size by marking corners with pencils in the ground and running string between pencils. You can build a transect square out of PVC pipe that can be disassembled and assembled quickly. You can use a hula-hoop. The size, transect shape and materials for making the transect just need to be determined ahead of time so that all groups of students use the same transect in the same ecosystem so the results can be averaged fairly. In order to establish exactly where you begin the first point of your transect square or center of your transect circle, one can throw a rock over their shoulder. Wherever it lands is either the first point or the center.
Abiotic factors such as soil temperature, type and percolation rate and weather data need to also be collected at the transect site. Soil characteristics and climate are the determining factors for the representative plant and animal populations.
Going to different ecosystems and collecting the same data for comparative purposed could be a valuable and exciting investigative experience that brings students to a true understanding of what makes an ecosystem what it is. In addition, it is what real scientists do. It is a real life meaningful endeavor.