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Biology: Introduction to the Fungi


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About this Lesson

  • Type: Video Tutorial
  • Length: 11:26
  • Media: Video/mp4
  • Use: Watch Online & Download
  • Access Period: Unrestricted
  • Download: MP4 (iPod compatible)
  • Size: 123 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: Fungi (2 lessons, $3.96)

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 http://www.thinkwell.com/student/product/biology. 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.

About this Author

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Founded in 1997, Thinkwell has succeeded in creating "next-generation" textbooks that help students learn and teachers teach. Capitalizing on the power of new technology, Thinkwell products prepare students more effectively for their coursework than any printed textbook can. Thinkwell has assembled a group of talented industry professionals who have shaped the company into the leading provider of technology-based textbooks. For more information about Thinkwell, please visit www.thinkwell.com or visit Thinkwell's Video Lesson Store at http://thinkwell.mindbites.com/.

Thinkwell lessons feature a star-studded cast of outstanding university professors: Edward Burger (Pre-Algebra through...


Recent Reviews

EXCELLENT! Exactly what I was looking for - sex...
~ Marilyn7

I was having trouble understanding the alternation cycles of fungi. This video explains it very clearly.

EXCELLENT! Exactly what I was looking for - sex...
~ Marilyn7

I was having trouble understanding the alternation cycles of fungi. This video explains it very clearly.

I've got a question for you. What's the biggest organism on the planet? Did you say the blue whale? I knew you would say that, because a lot of people think that the blue whale is the biggest organism on the planet. In fact, you've heard "the blue whale is the biggest organism that has ever lived." Well, there's one thing wrong with that statement, and the word is "organism." The blue whale is a big animal. But probably the biggest in terms of area, organism on the planet, is a fungus. Yes, a fungus.
Now, you're saying, "A giant mushroom?" That's because all you think about when you think about fungus is a mushroom. You have so much to learn. Do you realize that there is a fungus in Washington state that covers several counties? Well, how could people live there? See, that brings us to a story. Let's talk about fungi.
Now, fungi, if you think about it, our whole Phylogenetic history, we call fungi multi-cellular heterotrophs. Fungi, by definition, are multi-cellular heterotrophs. Well, does that mean that you and I are fungi? Well, no. But we're multi-cellular heterotrophs. How can you be a multi-cellular heterotroph and not be a fungus? Well, there's more. They also absorb food differently than you and I and members of the animal kingdom. They don't take in their food and hunt it down and have this whole digestive tube. They take in their food by absorption.
Let me give you a good example. Have you ever had athlete's foot? That's a parasitic fungus. What does it do? It itches. Do you know why it itches? Because it's a fungus and it's taking in food the way fungi are supposed to do. all it does is it grows--we'll talk about the terms in a minute--but it grows these little strands, these things in between your toes, and it secretes digestive juices and it melts your tissue and then absorbs it. What do you do? You kill it, just because it's starting to earn a living. So they take in their food by extra cellular digestion and then absorption. I don't want to give you the wrong impression--there are some fungi--nothing is ever simple. There are some single-celled fungi, and we'll talk about those, but generally, or generically, we've got to say that they're generally multi-cellular heterotrophs.
Lt's talk about some of the anatomy of fungi and then we'll talk about their classification and why we've broken them up. A fungus, generally speaking--and this is why you don't see giant mushrooms. That's just something called the "fruiting body." That's just how it reproduces. The real critter--the real thing is underground, and it has all of these fibrous extensions that spread out underground, sometimes for miles and miles and miles, and these are called hyphae. One is a hypha. You don't usually see one unless you look at it under a microscope. What a hyphae is--there's two different kinds. This is going to be important when we start talking about the way these things are classified. Take a look at this. This is a typical hyphae under a microscope and you see that there are divisions or septa in here. Well, this is one type of hyphae and it has septa, and it's separated. So notice I'm not calling these cells. They're septas. It's divisions within the hyphae.
And then there's another kind of hyphae. See any septa there? No, you don't. So we're not going to have septa on this one. This particular one is called coenocitic. So I just want you to remember those words, because what I'm going to be referring later on to coenocitic hyphae, this is what I'm talking about. Notice, you have a multi-nucleated hyphae with no divisions, no septa in there. And that, morphologically, is a way we're going to differentiate the fungi and say, "Ah, this kind has coenocitic hyphae, this kind doesn't.
Now, another thing. Not only do they have these hyphae, but the hyphae form these giant masses, and the masses are called "mycelia" or "mycelian." These are masses of hyphae. Next time you're out picking mushrooms... Let me tell you something. I keep talking about mushrooms. We're going to get to mushrooms probably in the next lecture, but you know, mushrooms are kind of scary things and you probably shouldn't just go out there randomly picking them because some of them are pretty poisonous. But if you ever see a mushroom laying on the ground or you go to the grocery store and you see a mushroom that's been picked, you can sometimes see strands coming off the bottom, and the non-biologist would say, "Oh, those are its roots." You'll never say that again, will you? You will say, "That's its mycelia," because that's what that is. That's the hyphae mass called the mycelia.
That tells us something about mushrooms and fungi in general. They used to be in the plant kingdom. But if you think about what we now know about plants and why we've had to break up our phylogeny, it's because... They're closer to you than they are to plants. Think about it. These things don't have chlorophyll. They don't have roots, they don't have stems, they don't have leaves. Why did they call them plants? Do you want to know why they called them plants? Because they were in the ground. Hello? That's not a good reason to be a plant in the new millennium. So molecularly, biochemical, DNA evidence, their cell walls... Okay, yeah, these things have cell walls, but guess what? Their cell wall is made out of a substance called "chitin," as opposed to a plant, which is cellulose. You know that. Well, you've heard of chitin before. Where do you find chitin? You find chitin in the exoskeletons of animals. So this whole idea of fungi being a plant--if you had that concept, get rid of it.
So all of this being said, and we're going to talk to you about the different fungi, how do we break them up? Well, we've broken them basically in four divisions. Four divisions--that's left over from the days when they were plants. So we're not really going to talk about phyla here, but divisions. The four divisions of fungi--I'll just give you a list, and then we'll work from this generated list as we go through the fungi. Hold up. We'll talk about the phylogeny of these things in a minute.
Okay, the first one are affectionately known as "chytridiomycota." The other ones, the next ones, are the zygomycota. I'll tell you what that means. We're just going to have so much fun with these words--zygomycota. The third one, the ascomycota. See anything in common here? And the fourth one, the basidiomycota. We're going to talk about these. And I want to start going over one thing that they all have in common--a life cycle. See, to be a fungus, generally speaking, most fungi have this life cycle I'm about to show you, and it's a little bit bizarre. It has these sexual/asexual stages, two of them, and we call that an alternation of generations between a sexual stage and an asexual stage. Let me show you how it works.
Remember, the creature itself is grown underground. So it's growing underground--I'm going to be real generic here--and it's got these mycelia. We're going to start off with mycelia, and the mycelia are going to mate. Fungi has sex. We don't call it sex; we call it plasmogamy, but you can call it sex. What happens during plasmogamy is you're going to get--now, this is what's a little bit bizarre--you get a nucleus from one and a nucleus from the other, but they don't fuse. So it's not true sex in a sense that it's followed by an immediate fertilization event. You're going to get something called a dikaryotic cell. That process that does that is called plasmogamy. It's spelled kind of like plasmo-gamy. You get a dikaryotic cell, two nuclei, and then we get an interesting thing--we get a fusion, and we're going to get a 2N cell. That fusion is called karyogamy. You can call it fertilization if you want, but you might as well learn the right terms, and that's going to be a 2N cell. Now, that 2N cell is generally going to go through a process where it's going to do a reductive division. Do you remember what that's called? It's called meiosis. And from meiosis you're going to get something called--well, it's usually a structure, but you're going to get spores, and from those spores you're going to get germination, and from that germination you're going to get mycelia.
So you see, look what we have here. We have a fertilization event, and then we have a meiotic division, and then, to get germination, we're going to do a process called "mitosis," which is asexual, which is kind of cool, too. But that's not all. They have a little side thing they can always do if they're not mating, and that's asexual reproduction. So the mycelia can simply form a spore-producing body, and the spore-producing body can then form spores, and then the spores can then form--guess what? They can germinate. This is sexual here, and this is asexual. So not only do they have a choice, but within the sexual cycle they have a sexual and asexual stage. That's cool stuff, and you're going to see that consistently throughout the fungi, you're going to see those two cycles.
Now, if you didn't get all that vocabulary, I want you to watch that one more time and make a good list, okay? Because all of those words are going to be important on the next lecture when we take a look at the four groups of fungi, so hang in there.
The Evolution of Life on Earth
Introduction to the Fungi Page [2 of 2]

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