Activity: Life in a Drop of Pond Water

Goals:

To use a microscope to search for microorganisms

in a drop of pond water.

To experience Leeuwenhoek’s discovery of animalcules.

Background Information: Microbiology is a branch of science that deals with the study of microorganisms. In 1676, Anton van Leeuwenhoek, a Dutch businessman and amateur microscopist, sent a letter to the Royal Society in London describing what he had seen in a drop of water. He called the tiny wee beasties animalcules, meaning “little animals.” Today we know these single-celled organisms to be bacteria.

Unfortunately, like many scientific pioneers, Leeuwenhoek was not taken seriously. They wondered how any living things could be invisible? You’ll soon find out when you observe a drop of pond water!

Materials: a blank slide, cover slip, specimens taken from a pond water culture, eyedropper or straw, identification chart of pond organisms

Procedure:

What I Know: Write two sentences explaining what you already know about what organisms that may be found in pond water.

Using an eyedropper or straw, place a tiny drop of pond water culture on the center of a blank slide.
Carefully, lower the cover slip onto the pond water.
Place the center of the slide over the opening of the stage.
Focus the specimen under 40X, then 100X, and finally 400X. Don’t be afraid to move the slide around to get different views of your specimen.
Decide which power offers you the best view of the culture. (You’ll probably want to use 100X.)
Some microorganisms move very quickly. You may even have to move your slide around to follow them.

What I Observed: Make a drawing of your specimen at the power that gave you the best view. If possible identify your organism by using the handouts at your station and/or the student computers. You can also go to

or type in Pond Life Identification Kit in your search box and it will take

you to this link.

Write a caption describing your observation.

Magnification

_____x

Caption:

What I Wonder: Pose a question that you may still have about the topic(s) related to this activity.

Question: Answer the following question in letter form.

Anton van Leeuwenhoek was the first to document the existence of

microorganisms. Read the Letter from Leeuwenhoek distributed in class

and write/type a response in letter form.

Write your answers to his questions in the form of a letter.
Remember that van Leeuwenhoek knows nothing of science beyond the 18th Century. You can concentrate your answers on the impact of the microscope on biology and ignore the other areas of science.

(This activity came from Marcella Dawson. See http://softlib.rice.edu/CRPC/GT/dawsonm/Lessons)