Fresh Water Ecosystem Science Fair Projects

Fresh Water Ecosystems

Fresh water ecosystems include any body of water that that does not have a high salinity level. They include lakes, rivers, streams and ponds. When collecting samples from these fresh water systems make sure you dip your collection nets in a solution of bleach to prevent contaminating the water with external bacteria and harmful microorganisms.

Objective

Grade Level: Middle/ Upper Level - Elementary School

Periods: 4-40 minutes

To observe the wealth of living organisms in a drop of water from our freshwater ecosystems

To classify the types of organisms observed as single-celled or multi-cellular

Use a key or chart to identify and name the organisms found

Background

Ecologists divide freshwater ecosystems into bodies of running water and bodies of standing water. In the latter the current slows and most suspended particles settle to the bottom. Lakes and ponds are bodies of standing water that will serve as the sources for water samples to investigate freshwater ecosystems.

Protists, which comprise many of the organisms found in the water samples, are mostly single-celled microscopic organisms. They have a nucleus and other cell parts. There are three groups of protists: protozoans (animal-like protists), algae (plant-like protists), and fungi.

Materials

Pond water, lake water, microscopes, slides, cover slips, droppers, paper towels, small dishes, key of freshwater microorganisms (obtained from a book such as one of the references listed below)

Strategy

1. Teacher will collect enough pond/lake water in order for each student to have his/her own sample.
2. Review usage and handling of a microscope during period 1.
3. Explain the steps for preparing a slide (period 1). Each student will be required to prepare a slide using the water sample(s). Place a drop of water on the slide and cover with coverslip, make sure no air bubbles are present.
4. Observe the slide under the low power objective lens and search for protists. Watch also for movement.
5. When you find some protists that are not moving or moving slowly switch to the high power objective lens.
6. Draw your protists within circles (about 8 cm in diameter) drawn on sheets of paper.
7. Note the eyepiece and objective lens magnifications and calculate total magnification. This is the eyepiece magnification times the magnification of the objective lens (both should be marked right on the lenses).

Performance Assessment

Draw and label living organism observed under the microscope.

Use the key to identify and group organism(s) found in the water samples.

Conclusions

With all life, irrespective of scale, there is a continual struggle and competition for survival. A pond is a miniature cosmos. A diverse range of living forms, both animal and plant, compete for energy supplies, food, space, and other resources. 3rd party contributor