I usually discuss the concept of 'red tides' with my students on this page. For those with any sort of classical history knowledge, I use a 'pyrrhic' victory (a very bloody victory) as a reminder for the name of this group. I also ask if they want to hold a diatom...and toss them a piece of chalk, explaining how the chalk is composed of diatoms and clay. If you bring in any scrubbing powder, such as BarKeepers Friend or BonAmi, you can put it on a slide, add a bit of water, and sometimes see some diatoms. If they're still alive, the blue-green algea in the large jar on the window is FULL of Euglena and some paramecia. It's very easy to set a slide of it up; I leave it running during lab as a sort of 'biological screen saver.' Water from Research Park pond or a ditch should also have lots of Euglena in it, and the students generally enjoy looking at all the cool stuff, from Nematodes to algea that they recognize, in the water. If the class is starting to get boring and the students are getting distracted, this is a good way to refocus them on the subject. There are good slides of Ceratium; I often use that as a quiz organism. Keep pointing out the number and type of flagella of each organism, those are important characteristics. For Vaucheria, it's very difficult to find a definite male hook with oogonia. Sometimes you can, but I'd suggest looking thru the slides and perhaps marking with a sharpie the area that has the sexual reproduction projections. For the Certium, I use the analogy of throwing a football....as it spins, it goes in a straight line. The girdling flagella of a ceratium spins it as it swims, and it moves in a direct line as a result.
As you go thru this section, show them the club chart of the phylogeny of the protista kingdom. Have the students write on it (I suggest they make several copies) what the photosynthates are, the accessory pigments, and the chlorophyll types. Also mention a bit about how Euglenids were once thought to be animals, then plants, then animals, then plants.... The BEST picture of Euglenids is probably one in the Atlas or textbook, I forget which. It's very hard to point out the anterior eyespot, but if you look thru a slide of euglena (and you can point out the different shapes they're twisted into) you should be able to focus on the groove and the "pouch" at the end where food is taken in.