Microcritters (FBCEC)


Participants will use compound microscopes to view the life in plankton samples, learning about the tiniest inhabitants of streams, lakes and ponds. If time permits, they may use plankton nets to collect their own Crooked Creek or pond plankton samples.

Grade Level:

7 - 12

Recommended Setting:

Indoor or outdoor classroom

Outdoor Activity:



Fred Berry Conservation Education Center, Yellville, AR


Education Program Coordinator, 870-449-3484



45 minutes - 1 hour

Suggested Number of Participants:

Up to 24

Special Conditions:

Additional time is needed if students are to collect plankton samples.


  • Discover the life in a drop of surface water (pond, creek or other source)
  • Practice using a microscope.
  • Identify local phytoplankton and zooplankton.

Key Terms*:




*See glossary for definations


  • Beakers
  • Compound microscopes
  • Cotton balls
  • Droppers
  • Forceps
  • Lens paper
  • Methyl cellulose (to quiet organisms)
  • Paper towels
  • Plankton identification resources
  • Plankton samples, (nets and collection supplies if participants will be collecting)
  • Pupil cam, flex cam and laptop computers
  • Slides/cover slips


Plankton is the minute plant and animal life (phytoplankton and zooplankton) that floats on water surfaces and is the foundation of most marine and aquatic food webs. A drop of surface water has interesting microorganisms for viewing in “live action.”



  1. Show how to use the compound scope. Identify the stage, objectives (low, medium and high power), the coarse and fine adjustment knobs, the on/off switch and the lever to adjust the iris. Demonstrate how to focus on the specimen. Begin at low power and use the coarse adjustment knob to bring the object into focus. Next, if higher magnification is needed, center the specimen in the field of view and rotate the medium power objective into place and use the fine adjustment knob to bring the object back into focus. If still higher magnification is necessary, repeat the process with the high-power objective, making sure to use only the fine adjustment to focus. Never use the coarse adjustment knob with medium-and high-power objective lenses. It is possible to break the slide and damage the lens.
  2. Demonstrate wet mount technique. Place a drop of the plankton sample onto a slide, carefully lowering the cover slip from one side to eliminate most of the water bubbles. Dry any excess liquid by gently touching the edge of a paper towel to the slide.
  3. Participants are to prepare and view slides using the plankton samples. They may find a variety of single- and multi-celled organisms. Use the classroom resources to identify them.
  4. Project interesting specimens onto a screen with the projector (hooked up to a pupil cam/scope/laptop computer).
  5. Clean slides and dry with paper. Check microscopes to see that they are left on 4X objectives and turn off the power.
  6. Ask if the presence of “microcritters,” such as the ones they viewed, indicates a healthy or unhealthy body of water. Teach them that, although drinking untreated water is ill-advised, plankton forms the foundation of an aquatic food web and is a vital element of a healthy aquatic habitat.


  • Demonstrate how to prepare and view a wet mount slide
  • Describe the observations of the organisms. What did they look like? How did they move? What were they doing?
  • Explain how the absence of plankton would affect an aquatic ecosystem.



Phytoplankton – plant life found on a body of water


Plankton – the passively floating or swimming minute animal and plant life on a body of water


Zooplankton – minute animal life found on a body of water