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LIFE IN A DROP OF WATER
Grade Level: 9-12
Subject: Science (Biology)
Time Allotment: Two to three 45-minute class periods
BUILDING BACKGROUND
In the activity, students review the four phyla of protozoa living in water.
 STEP 1
Teacher reviews the structure, function, and examples of the four phyla of protozoa: sarcodina (amoeba), ciliophora (paramecium), zoomastigina (giardia), and sporozoa (plasmodium, malaria).
- If the teacher chooses to display or hand out diagrams of the single-cell organisms, websites containing cell diagrams are included in the materials section.
Students take notes on each phyla.
 STEP 2
Teacher explains that the class is about to research single-cell organisms in tap water and one other type of water: pond, lake, river, ditch, or bottled. (Teacher chooses second type depending on what is most available. A natural source is recommended for more diverse lab results)
Students predict what types of organisms they will see in Sample 1: natural source and in Sample 2: tap water.
LEARNING ACTIVITY 1
In this activity, students use a microscope to record observations of protozoa in a water sample.
- Students should conduct the Life in a Drop of Water Lab in pairs
STEP 1
Lab groups place a drop of Sample 1 on a slide and cover carefully with a cover slip.
Examine the slide under low power first to find moving objects. Then, increase to medium and high power.
Using the Magnifications Handout, students should sketch what they see in the microscope under the three magnifications.
STEP 2
Under the highest magnification, students should use the Water Survey Handout and record information on the different single-cell organisms contained in their water sample.
 STEP 3
Students fill in the Life in a Drop of Water Conclusions worksheet for Water Sample 1
LEARNING ACTIVITY 2
In this activity, students use a microscope to record observations of protozoa in a sample of tap water.
STEP 1
Lab groups place a drop of Sample 2: Tap Water on a slide and cover carefully with a cover slip.
Examine the slide under low power first to find moving objects. Then, increase to medium and high power. (Students do not need to repeat the Magnification handout.)
STEP 2
Under the highest magnification, students should use the Water Survey Handout and record information on the different single-cell organisms contained in their water sample.
STEP 3
Using information from Water Sample 2, students complete all of the Life in a Drop of Water Conclusions handout.
CONCLUSION
Class discussion using Life in a Drop of Water Conclusions as a guide
- Give particular focus to water filtration and diseases
EXTENSION ACTIVITIES
Many scientists believe that paramecia are more complex than amoebas. What characteristics do paramecia have that might justify this statement?
Write a persuasive essay arguing whether movement by cilia or movement by pseudopodia is more efficient.
Write an expository essay on one of the diseases caused by drinking dirty water.
Choose one of the four phyla and create a three-dimensional model of the single-cell organism.
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