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Biology

Biology Lab: Microscope observations of Protitsta

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Lab Exercise

Biology Lab: Plant Transport and Transpiration

Goal: To observe microscopic forms of life, particularly protists

Materials

Safety note: Always wash your hands carefully after working with your sample, and avoid touching your face (mouth) or eyes (tear ducts) with pond-wet hands. Ducks are one of the major vectors in the spread of certain kinds of disease, especially flu.

Procedure:

  1. Collect a water sample from a local pond, rain gutter or other standing water outdoors.
    1. If you don't have a pond handy, put about 1 cup of water in a clean jar.
    2. Let stand overnight so that all the chlorine will evaporate.
    3. Add about two tablespoons of dirt and some decaying organic matter (try getting the dirt from underneath a plant).
    4. Let the water stand for a day in a warm place near a light source but out of direct sunlight. You should have some protists swimming around in it by then
  2. Use the eyedropper to place a drop of water in the well of the well slide.
    1. If you don't have a well slide, put the drop of water on a clean, flat slide.
    2. Place the slide UPSIDE DOWN on the stage of your microscope so that the drop is suspended over the hole; don't smear the water.
    3. Now your observing surface is flat.
  3. Observe your sample through the microscope at low power.
    1. How many different kinds of protists do you see? If possible, draw some of them. [You won't be able to send me the drawings in your email report, but drawing them will help you focus on their features.]
    2. Using the measurement you made in earlier labs for your field of view, estimate the size of your protists. For example, if your field of view is 1 mm at 40X, and the protist you observe takes up about 1/4 of the diameter of the field of view, then your protist is about 0.25 mm long.
  4. Observe some of the protists at higher power.
    1. What details are visible now that you could not see at low power?
    2. Do any of your protists have cilia or flagella?
    3. How do they appear to move?
    4. If possible, identify your protist as a member of one of the major groups (see web lecture).

Report: Your report should include the explanation of how you obtained your sample, and a description of each of the protists you observed.

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