Introduction:

Background:
The soil is home to the largest biodiversity on this planet;  a fascinating world of micro-organisms. The most common being the bacteria, fungi and algae.  However, they are not the only forms of biological and ecological significance, of equal importance are: protozoans, earthworms, nematodes and insects. This investigation will focus on a method of locating Amoebae, members of the protozoa.

Protozoa are unicellular, eukaryotic microorganisms. The Amoebae move by means of pseudopodia. Many of them obtain their food by holozoic nutrition characterized by direct feeding on microbial cells such as bacteria."It has been estimated that one species of Amoeba requires 40,000 bacteria per cell division. consequently bacteria must reproduce at a rapid rate to keep pace with their predators".(Alexander,1967.p.108)
This information suggests that the protozoa population are important in limiting the bacteria population maintaining a balance in this highly populated soil habitat. The amoebae survive unfavorable conditions by forming cysts.

They are usually found near the surface of the soil in the upper 6 inches in soils that are warm, moist, and rich in organic matter as this encourages a high bacteria population.They tolerate a range of pH with  a preference for acidity.

Since the soil is a complex habitat, with a rich biodiversity component; collecting amoebae will also show other organisms coming out of the soil. So this activity will lead to other investigations of the soil ecosystem.
 

Inquiry Process:

1. Characterize soil environments that would have the greatest diversity of microbes?
2. State your hypothesis that predicts the environment that has the greatest (#/diversity).
3. Select a variety of environments that meet your established criterion for microbial growth.
4. Determine a control to test your hypothesis against.
5. Choose from the following list of possible materials.

• Microscope and/or stereoscope
• Petri dishes containing a gel made from agar and water (no added nutrients)
• Containers and tools to collect the soil samples
• Soil samples from different microenvironments
• Sterile swabs and/or inoculating loops
• Plastic wrap/parafilm
• A culture of a suitable food bacterium, Enterobacter aerogenes
• Digital camera  or camera to record each site
1. Study the following collection and plating procedure.

• 1.   From each environment collect a sample and place in a collection container.
• 2.   Label the location on bag.
• 3.  Label plate with name, habitat, date.
• 4.   Place about a 1/4 teaspoon of the soil sample in the center of plate.
• 5.   Using a swab spread a circle of the food bacteria provided about 2 cm. from the soil sample.
• 6.   Cover plate, wrap tightly, and place upright in a cool dark place for 48 hrs.
• 7.   Make observations every 2, 4, and 6 days.
• Design your experiment.

Steps:

1. Write out your experimental design.
2. What method(s) are you going to use to analyze your data?
3. Draw/photograph all the organisms you observe on a separate sheet and indicate when they occured.
4. Analyze your data.
5. What conclusion(s) did you draw?