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Biology: Protists: Archaezoa and Euglenozoa


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About this Lesson

  • Type: Video Tutorial
  • Length: 12:27
  • Media: Video/mp4
  • Use: Watch Online & Download
  • Access Period: Unrestricted
  • Download: MP4 (iPod compatible)
  • Size: 134 MB
  • Posted: 07/01/2009

This lesson is part of the following series:

Biology Course (390 lessons, $198.00)
Biology: The Evolution of Life on Earth (34 lessons, $64.35)
Biology: Final Exam Test Prep and Review (42 lessons, $59.40)
Biology: Protists and the Origin of the Eukaryota (2 lessons, $4.95)

Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science. Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel. His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp. He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

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Okay you guys, I know you're sitting at that computer and you are ready for diversity of protists, but I want you to buckle in first, because this is a topic that, you know, if you watch this same lecture next week it could change if Thinkwell could do that, because we are about to enter probably one of the most controversial and-what's the word?-confusing, maybe-parts of systematics. Fights have broken out at protist conferences over the stuff I'm about to tell you, and there's a reason for that, because as we get into this three-domain system, and we go into this kingdom, eukarya, or this domain, eukarya, things get crazy.
Let's do a quick review. I've got a little chart here. We're going to play with this for a long time. Let's just review what the three domain system says, because pretty much taxonomists, systematists all over the world are going, it looks like, to the three-domain system. If you remember, we broke up the bacteria and the archaea.
Now, review of history. Back in the old days-well, three or four years ago-we pretty much had this kingdom called "monera." Remember that? The monera were all these one-celled prokaryotic things, and we called them one-celled prokaryotic things because that's what they were. We said, "You're all monera." But then as we started to get into DNA evidence, into ribosomal evidence, and we've really gotten into the molecular biology in the past half a decade or so, we realized, "Oh my gosh, the only thing they have in common is they're one-celled and prokaryotes, but they're so different that that classify as different things. They're not even in the same kingdom." And in fact, if you remember, the archaea were split off, and they're actually closer, sort of, to you and I, than they are to some of the other bacteria.
Well, that being said, we decided, all right, so we're going to have a three-domain system, and we have the bacteria, we have the archaea, and we have the eukarya, all those things that are eukaryotic-eukarya. Well, it's this domain I want to talk about now, and specifically a group in that domain that-kind of a protist that you and I-I've got to tell you, even the word "protist" isn't going to be real meaningful anymore, guys, because we used to have a protist kingdom and by the end of this lecture you probably shouldn't talk about a protist kingdom anymore.
So like I said, buckle in and let's go, and let's talk about these things. I am now going to start using a generic word. The word "protist." So in these past five seconds I have changed the word "protist" from the word for a kingdom to a generic word, like "kids" or "laundry." That's what protists are going to be between you and I right now.
Well, why have protists diverged so much? Well, they're old. Protists branched off an awfully long time ago and they reproduce very rapidly. And so the point is with this rapid reproduction and this very ancient group, the protists literally have diverged more than any other organism on the planet. Do you realize there are 60,000 different species of protists? Over 60,000. Imagine 60,000 different pieces of laundry, because that's what we're talking about here.
Well, in the old days we used to break the protists up into animal-like protists, and it was pretty generic, although a lot of people figured, "Oh, this is a phylum name." Well, it is. We used to call them the "protozoa," which were the animal-like protists. Then there was another group called the "algae," which were the plant-like protists. And then there were some that were neither plant-like nor animal like, and they didn't even have a name. We called them the "not protozoa or algae." They were the fungus-like things. All of this is ridiculous anyway, because listen to what I'm saying. I'm saying the protozoa are animal-like creatures. It should be the other way around. The animals are protozoa-like creatures, because they were here first. But the good news is, we got rid of that. But the bad news is, we got rid of that. That's phylogenetically wrong.
When we started tracing evolutionary history and molecular biology, everything I'm about to tell you is going to be about molecular biology now. We are going to see that the DNA evidence, that the evidence we are building from molecular systematics is giving us a completely different picture, and the diversity of the protists, and the convergent evolution-remember that term?-that has happened within the protists is incredible. So allow me to keep using this word "protist" and we will now break that group down into what they're really going to be. Let's see why.
First of all, what we may end up doing, when all of this is said and done and the protist dust settles, is we may end up with five kingdoms of protists-of what used to be called protists. One, two, three, four, five. And we're going to fill these in over the course of these lectures.
Now, if you'll notice here an interesting thing. Now, this is a timeline, and if you look at this timeline you can see that here's our very first cellular ancestor, and off came the bacteria and then off came the archaea, and there's a whole grouping over here-and I'll tell you the end of the story. These are plants, animals, and fungus, so they're at the end of the story. But if we take a look over here we see that there are two groups in the eukarya that branched off before all of these. And these would have been, in the old days, and I'm going to keep saying that-protists.
Well, let's take a look at these and let's name the first one. I'm just going to call it A, because I can't fit it all, but we'll fill that out on the artwork for you, and this is a candidate kingdom archaezoa. It's not a kingdom yet. We call them "candidate kingdoms," hopeful kingdoms. They hope to be a kingdom someday. But that was a very early divergence. Now, why is that so early? Why are the archaezoa considered so primitive? Well, I want to go back to something you probably know about. Remember the Lynn Margulis hypothesis about endosymbiosis and the fact that the mitochondria was actually an endosymbiotic bacteria that got taken up in a eukaryotic cell, and it gave it the ability to do the whole aerobic respiration story? In fact, we think a lot of our organelles, the organelles of organisms, of eukaryotic cells, may have been taken up this way. Well, one would suspect then, that there might be some kind of eukaryotic cells out there that don't have mitochondria or there once were. Well, guess what? Archaezoa, which means ancient, don't have mitochondria. So systematically we're thinking, "Wow, these things are really old. Notice I'm smiling because there's a rest of the story coming in a second. So they lack mitochondria. Their DNA clocks also suggest a very ancient divergence. They're biochemical systematics.
What's a good example of this? Do you ever hear of the disease, giardia? This is a parasite. One of the things about these protists is a lot of them like to live in our bodies. Remember, they've diverged enormously. They've been around a long time. This is an intestinal parasite that's often passed through drinking water. It causes diarrhea and all sorts of nasty things that we don't want to talk about. But anyway, I want to leave archaezoa behind because I've already told you why, but I have one last story to tell you. We're not sure that they really have always lacked mitochondria because when we check our their genetic sequence we find genes-you're not going to like this-genes that code for mitochondrial proteins. So did they once have mitochondria and have they lost mitochondria? Did they maybe pick it up through some kind of sexual reproduction? Who knows. We don't know. But archaezoa, candidate kingdom number one.
This next kingdom is probably near and dear to any of you who ever took high school biology because you probably have seen them before. I'm going to put an E here for euglenozoa. Euglenas are friends of yours. Euglenozoa-DNA evidence suggests that they branched off after the archaezoa. Let me draw a euglena for you. A euglena is a flagellate, which means it has a long flagellum. You may recognize the fact that it has an eye spot. Like so many of these things-and it has chloroplasts and a nucleus, etc., etc. But the thing about the euglenoids is that this is a type of protozoan-here's some vocabulary for you-called mixotrophic. There's a new word for you. Have you ever heard of autotrophic? I know you have. They make their own food. Have you ever heard of heterotrophic? I know you have. It takes in its food. What do you think a mixotrophic does? Mixes. This eye spot allows it to go toward light and do photosynthesis, but if it's in the dark it can actually absorb by osmosis and diffusion the nutrients that it needs.
Now, the Euglenozoa are part of a group called the euglenoids, but there are others in this one, too. For example, there's one called a "kinetoplastid." This is another member of this group. I just want to mention this one. Why? Because these things have a structure called a kinetoplast. Now you know why they're called kinetoplastids. The kinetoplast has one mitochondria associated with it and it has extra nuclear DNA. So this kinetoplast has DNA on its own. What is it doing there? Why is the mitochondria there? Well, nobody's exactly positive, but it is a systematic thing that is in common with all of these.
Why do I want to tell you about these? These can be nasties. Did you ever hear of the disease African Sleeping Sickness. Right here. This can cause African Sleeping Sickness. So not all euglenoids are these friendly little guys you can see under a microscope.
All right. Just to summarize, we've see our two out groups, so to speak, the two that have come off, but now we have a whole group that seems to have a common ancestor. That's going to be some interesting fodder for our next lecture.[]
The Evolution of Life on Earth
Protists and the Origin of the Eukaryota
Protists: Archaezoa and Euglenozoa Page [2 of 2]

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