Lesson 10: You Care Alot About Eukaryotes?

One kingdom down, four to go. Let’s take a look next at the other kindgom that is mostly made of of unicellular organisms…Kingdom Protista.

Take a look at some sample members of Kingdom Protista:    See how diverse they are? Some consist of only one cell and others, like the algae on the bottom row, are multicellular.  Some are heterotrophic and some are autotrophic.  Some can move on their own and others must rely on the current of the water in which they live to move them.  Some live alone and others live in groups, called colonies. 

We are going to spend some time looking closely at many of these examples over the next few lessons.  Let’s see if we can get a real-life glimpse of a few live protists before we begin.

You can order live protists from a science supply company like HomeScienceTools, but the best way to observe a good variety of protists is to collect your own.  They all require an aquatic environment, so the best place to gather a sample of protists is in a local pond or other stagnant water source, like a horse trough or rain puddle.  Collect some pond water, get out your microscope, and see if you can find some microscopic protists.  The best way to collect the water is with a long ladle.  Scrape some water from the bottom of the pond and place it into a jar.  Try to choose a warm, dark spot.  Make sure to get a little mud from the bottom into your sample.

If you want, you can culture your sample for a few days first.  Culturing is a means by which scientists try to increase the number of organisms in a sample by feeding them and providing environmental conditions the organisms like.  We cultured bacteria in our cupcake paper bacteria food.  Pond protists prefer a dark warm environment with lots of food, so if you want to culture your organisms first add a little food to the jar, like a tiny bit of hardboiled egg yolk or a  few grains of uncooked white rice. Then wrap the jar in aluminum foil to keep out the light, poke a few holes in the lid for air, and leave it in a warm place for a few days (like the laundry room). 

When you are ready to look for protists, prepare a wet mount slide.  Use an eyedropper to draw up a drop of your culture from near the bottom of the jar.  Drop the sample onto the center of a clean slide.  It is better if there is a bit of food or dirt in your sample so that you can focus the microscope accurately.  Carefully add a coverslip. 

Begin scanning once you have focused on the microscope on a bit of food or dirt.  Scan on low power until you find an orgaism to watch.  Once you locate one you can increase the magnification.   Be patient.  If you can’t find something after a few minutes of looking, try another slide.  Try to draw what you see on a sheet of microscope paper.   Don’t worry if you can’t find any specimens – although it is great fun to watch actual microorganisms on a slide, we will have a chance to observe some short videos of protists and you will hopefully look at some prepared slides of the organisms we study.