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Here I share how I teach a 7th grade lab on finding protists and microscopic animals in pond water. This may seem daunting if you are not familiar with the organisms or haven’t had the time to organize the activity. I hope that I’ll give you all the information you need for a successful lab.
Why take the time for this lab? Well, no one is going to be excited about algae by looking at a picture of it. Algae in the macroscopic world is called POND SCUM, but under the microscope it’s BEAUTIFUL.
Also, many standards can be addressed in a pond dip lab:
The supplies are simple and usually found in the typical middle school or high school biology classroom. The only things you will need to gather otherwise is the microorganism-rich water and organism keys; I provide you with information on both.
Warning: Do NOT add tap or bottled water to your pond water. Drinking water usually has some chlorine in it – this will kill your organisms! If I need additional water for rinsing slides I use water that is treated with water conditioner for fish tanks. The conditioner removes chlorine.
I have my students do this lab after we have studied the basic characteristics of the 6 kingdoms of life. In this lab we can study the protist kingdom as well as microscopic animals. Since we always are lucky to see crustaceans, worms and rotifers (amazing little animals!), my students are able to observe the differences between the animals and the single-celled protists.
The key, I think, is that your students should become a little familiar with the organisms before beginning. I show some videos on actual pond water organisms (always creates excitement for the lab) in addition to some other videos about the protist kingdom.
pond life video (fast forward past the tadpole to learn about protists)
Additionally, I review the possible types of microscopic animals we hope to find. Lastly, my students complete my Virtual Pond Dip WebQuest a few days before.
First, students will need to know how to use the microscopes. With the concavity slides, my students are able to use the low magnification (100x), but not the high because the lens would go into the water.
Second, model how to make the slide, use the slide to find organisms and clean up the slide.
Third, explain that if what they see is not green and/or not moving it is not alive. Students naturally want every little thing they see to be an amoeba or hydra or leech! I give a clear direction – don’t call me over to verify that you are looking at sand particles or dead plant matter. If it isn’t moving or green, then just keep on looking.
Fourth, Model how to return the water drop to the container (I prefer to preserve my organisms for others to see as much as possible). I demonstrate that the drop should be poured into the container and then the slide should be gently tapped on the side of the plastic container to save as much of the water as possible. Another option is to rinse the drop into the container using a small squirt of conditioned tap water. Afterwards, dry the slide with a tissue before adding a new drop.
Fifth, Verification. All identifications have to be verified by me. However, students must tell me what they think they are seeing before I will check the microscope. Otherwise, students will use me as their ID key rather than the actual keys.
This Google Doc provides the information for my required documentation for 7th graders. Students must find 6 different organsims that meet the criteria. The 2nd page has the circles for their drawings. I recommend that students use only pencils and colored pencils.
Lab Performance Rubric. With trial and error (lots of error) I found that providing a lab performance grade keeps my students on task and following the lab rules. You might find this editable rubric handy.
If I had more time and if I were teaching this to high school I would add more criteria for the assessment. Ideas are for students to have to use information from the organism keys to justify their identification. Another would be to construct a food chain/web of the types of organisms found.
Please share your experiences or ideas with pond dips in the comments section below.
Need a way to encourage following lab rules? Try this: Science Lab or Activity Rubric – Promote Collaboration Skills! (New) Editable!