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Ken-A-Vision Experiment 2

A UNIVERSE IN A DROP OF WATER:
Studying organisms found in a drop of water

Objectives: To better understand how to gather samples and to observe living protozoan and other simple organisms.

Suggested materials:
· Small collecting jars
· Eye dropper
· Cotton
· Concave slide

· Petroleum jelly
· Slides-plain and prepared
· Cover slips
· Live sample

Vocabulary:
· Cilia
· Flagella
· Inference · Locomotion
· Macroscopic

· Microscopic
· Organelle
· Organisms
· Pseudopods

NOTES TO THE TEACHER:

1. The best all-around environment for collecting live protozoan or one-celled animals is from unpolluted ponds or lakes containing fish. Collect by using clean jars or pipettes from various levels and locations without agitating the water.

2. To maintain the protozoans collected, place a handful or hay (Timothy is preferable) in a jar then fill ¾ full with pond water. Set aside without a lid exposing the sample to moderate temperature only and away from direct sunlight.

3. Algae can also be collected from stagnant pools. Look for green "scum" floating on the surface.

4. Most living organisms when exposed to the intense light and heat of a microscope try to flee.

So, in order to observe quick moving microscopic specimens you can:
a. Use a few cotton fibers on a slide, adding the drop of pond water to it then a cover glass.
b. Add a chemical prepared by various science supply companies such as Protoslo to a slide sample which slows down the movement of microscopic organisms.
c. Scrape a small amount of petroleum jelly on the edges of each slide of the cover glass, then carefully lay the cover glass over the deep well/concave portion of the slide which holds the sample and press lightly. This will prevent the water from evaporating thus greatly expanding viewing time.

5. Have students use the low power objective to find specimens then slowly work up to hight power.

6. Live specimens can be purchased from most science supply companies at minimal expense. Some of the most common organisms used are: ameba, paramecium, Euglena, spirogyra, volvox, and hydra.

7. Commercially prepared slides are not as exciting as live samples, but provide an easy way to introduce any student to observing microscopic organisms. Ken-A-Vision would be a possible source for such slides.

8. Dichotomous keys used to identify various organisms can be purchased through science supply houses, checked out from school libraries, borrowed from experts, ordered through any local book store, or found in biology textbooks.

ENRICHMENT:

1. Encouraging students to research individual interests might lead to a science fair project.

2. Invite experts into the classroom to speak about such things as protozoan parasites, how these organisms are indicators of pollution and water quality, or a general information lecture or demonstration.

3. Have the students construct a simple classification system of microscopic animals based upon their differences on such characteristics as motility, shape, number of cells, or color. These classification activities can be expanded to include other living organisms.

4. It is easy to study the effects of chemical on protozoans by using such solutions of ink, vinegar, baking soda, salt, or sugar.

Activity: THE WORLD DOWN UNDER! or YOUR IDDY BIDDY BUDDIES!
Studying organisms found in a drop of water

Purpose: Observing simple organisms found in pond water

Procedure:
a. Use an eye dropper or straw to withdraw various samples from different levels in the container of pond water.
b. Each time, place one drop on a clean slide. Then top with a cover glass. It may take several attempts before you find a drop which produces many organisms.
c. If the organisms move around too quickly you can use cotton, chemicals, or a drop slide to contain them. Your instructor will advise you.
d. Draw and label what you see in the circles provided. Ask your teacher for a classification key.
e. If resources are available, identify various organisms observed. !

Conclusion:

a. How do the different organisms move?
b. How many cells make up organisms in each sample?
c. Why are these organisms called "simple?"
d. Describe how some are more like animals and how some are more plantlike in the various characteristics observed.
e. Compare the differences in the organisms which move and the ones which do not move.
f. How do various organisms react to light?
g. Can you identify any parts of the cell in some of the organisms observed? If so, label them in the drawings.