Homeschool High School Biology: The ProtistsThat Live in the Local Lake

You will never want to even touch pond water again after completing this biology lab.

But you WILL want to have an aquarium full of pond water living in your home so you can keep hundreds of thousands of microscopic protozoa pets!

This lab is a companion to CK-12 Biology 8.4, which is the chapter on protists.

Observing prepared slides of protists is a good preliminary lab, because it allows your high schooler to review proper microscope usage and how to make microscope drawings, and to get an idea what the live protists might look like. 

Here are the lab instructions that I wrote for my teenager, and here are the materials that we used for the lab:

• packaged sterile sample container
• eyedropper
• microscope
• (optional) microscope digital camera and software
• protist diagrams
• blank microscope slide and blank slide covers
• lens cloth

There was a blast from the past on the package of microscope slides:

I used to shop in that independent educational toys and teaching supplies store ALL THE TIME when my children were wee. The dollhouse I bought one toddler to celebrate her toilet training came from there, as did the PlaySkool circus set that the other kid picked out for her sixth birthday present, about an hour before she broke her leg on the playground and it turned out that a huge Playskool set was absolutely the perfect thing for a kid with a cast on her leg to play with for a solid month!

Fifteen years after picking out that dollhouse, my teenager collected water from a local lake, brought it home, dropped a single drop onto a microscope slide, and put it under the microscope to see what lives there.

A lot, it turned out!

In the above video, I think I see an amoeba, but I think that all the larger creatures are perhaps nematodes? I haven't even looked to see what the teenager identified them as in her lab notebook, but I'm sure her guess is better than mine!

The next video is by far my coolest:

I'm pretty sure those are stalked ciliates! The teenagers and I have done this lab several times, and I've only seen these particular critters once! I'm think all the critters swimming around them are Euglenae. Or maybe Paramecia? 

Those two videos are taken at just 100x, so you can see how much you can see even at that low magnitude. 400x, below, gives you more detail, but we don't use any additives to slow down our protists, so anything speedier than that oozy amoeba at the bottom right is hard to see.

This is a different water sample on a different day. I think that might be another Euglenoid because of its chloroplasts, which perhaps makes the critters that I previously thought were Euglenae actually Paramecia. I should probably get off my butt and go see what the teenager identified everything as, because I'm sure that she did more research than I'm currently doing!

The identities might be a bit sketchy, but the point of this particular lab isn't specifically to correctly identify every protist. Think of how much the teenager learned about sample collecting, microscope usage, and protists in general, as well as the practice that she got writing a lab report, problem-solving in science, and making decisions about identification. 

And most importantly, she got to see all the magic that lives out of sight in our local lake!

This protist lab pairs well with this macroinvertebrate identification lab, as well as this larger Water unit.