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Biology: Major Modes of Nutrition Among Organisms


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  • Type: Video Tutorial
  • Length: 12:01
  • Media: Video/mp4
  • Use: Watch Online & Download
  • Access Period: Unrestricted
  • Download: MP4 (iPod compatible)
  • Size: 130 MB
  • Posted: 07/01/2009

This lesson is part of the following series:

Biology Course (390 lessons, $198.00)
Biology: Cell Biology (28 lessons, $45.54)

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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You know, you guys have heard me talk a lot so far about the ability to take in energy. If you think back to the way we started this whole course, the ability to use energy is something that is a characteristic of life. Well, I have a question for you. Have you ever heard of the word "nutrition"? Well, that's not my question. I know you've heard of the word nutrition. That would be way too easy. I'm going to ask you what that means. In your own mind right now, did you just say that nutrition is eating? Because to you and I, yeah. But what's nutrition to say something like this? Now, this thing needs this so-called nutrition just like you and I do. But does it nutrify itself? So maybe I'd better ask you another question before I ask you that question. I should ask about this thing called a "nutrient," or what you and I refer to as food. I'm going to use those two words in the same way. What is a nutrient?
Well, a nutrient, or what you and I call food, is something that we get from our environment, but some things may not get all their nutrients from their environment. But ultimately, it's got to come from the environment because you are what you eat. You are what you photosynthesize or whatever. But a nutrient being food, let's define food. What is food? Food is a material that is going to contain elements that you can use for growth and repair of tissue. Think about that. Food is something that is going to give you stuff to make yourself bigger or to repair materials or to add new materials on. So what does food do? Food, number one, provides raw materials. Generically, we say that food also provides energy.
But I've got to tell you, what's up with this thing energy? What do I mean by energy? When I pick up a hunk of tofu-I don't pick up tofu very frequently, but I had to say that for you vegetarians out there-or a broccoli or a cheeseburger-it doesn't glow. Where's the energy in that? It's like this amorphous mass of nothing it looks like, but it has elements, and in those elements are electrons, and the key is those elements are held together as molecules, and there's different energy levels to those electrons, and with those different energy levels, as you're going to see in our respiration unit, you can pass that electron down from a high energy level to the next one, to the next one, to the next one, and in doing that, you can use that energy to make intermediate compounds. You didn't think food was all that, did you? But it is.
But that's not what I want to talk to you about right now. What I want to talk to you about right now is how organisms take in that food. We're going to spend lots of time on energy. I want to talk to you about the way organisms take in that food, and I want to teach you two general terms and then grow on those.
First of all, let's talk about the term "autotrophy." That is one major form of nutrition-autotrophic nutrition, or the autotrophs. Autotrophs-auto-self-making. These things make their own food. What do you mean, they make their own food? Do they make their own carbon so they can make protein? No. Remember what food is-it's a combination of elements that can be used to make new materials or that you can get energy from. That's what they're going to make. Do they need to take in raw materials to do that? Of course they do. Nothing exists in a vacuum. I'm sure you learned in middle school about photosynthesis. That's what this guy is all about. This is an autotroph. Why is this an autotroph? It's an autotroph because as we speak it is making its own organic food. Wait until you get to photosynthesis. I envy you guys. You still have to learn all that stuff. So anyway, they make their own food. We're going to do "food" in quotes because now there's this whole new meaning to the word "food."
So you say, "let's move on, Wolfe," but there are other autotrophs on the planet, too, not just plants, and that's why you're taking a biology course. For example, there's a whole group of organisms called "bacteria." Some of them are autotrophic. There's a whole group of things like cyanobacteria in the bacteria. These things-oh, I don't want to get going on those. I can go for hours on cyanobacteria. And there's even some things that... By the way, let me ask you a question and see if you remember from high school biology. Do you know what the substance is in here that allows these to do this amazing autotrophic process? It's a substance called "chlorophyll." It's a pigment. Well, guess what? There are even some prokaryotes, some bacteria, that have something called bacteria chlorophyll; slightly different than plant chlorophyll. It does the same thing. So those are autotrophs.
The other major qualification is called heterotrophs. Heterotrophs take in food, and what they're going to do with this food is two things. You know the answer to this one. Name a heterotroph for me. That's right. Yourself, your roommate, your friend, worms. Everything that's pretty much not an autotroph is a heterotroph. They are going to take in food and what they're going to do is they're going to use that food for energy and they're going to use that food for more material.
So an example of this will be animals, but there's a lot more. For example, there are some bacteria that are heterotrophs. Fungi-heterotrophs. Many of the one-celled creatures which we'll generically called "protusts" are heterotrophs. And now we're going to spiral in a little bit and choose the right terms for these things. Plants are what we know of as an example of something called "photo-autotrophs." It's an autotroph that uses photons with that pigment called "chlorophyll." On the other hand, animals are not autotrophs, they're heterotrophs, but what these do is they use chemicals. They have to take in chemicals, so we call them "chemo-heterotrophs," which brings us to an interesting question. Can we interchange this stuff? Is there such a thing as a chemo-autotroph? Or is there such a thing as a photo-heterotroph? You think I would ask that question is the answer was no? Let's talk about those.
Let's talk about chemo-autotrophs. Now, use your head-chemo-autotrophs. Think autotrophs while I'm writing. Done thinking? Autotrophs are things that make their own food, but what are they going to use for energy? Well, before, what we were talking about... Remember, we had chemo-heterotrophs. They were taking in food. Well, these guys are making their own food, but the energy is not going to come from light; the energy to make this food is going to come from some kind of chemical. So the energy used from chemicals, not light, but it's going to make its own food, make chemical bonds. There's a couple of groups of things that can do this. In classification we know that there are two groups of what we call "prokaryotic cells," those single-celled organisms, bacteria and archaea, to make it official, and a lot of these things do a very cool thing. For example, whereas photo-autotrophs-give me an example of a photo-autotroph. Okay, good. Photo-autotrophs take-so photo-I just want to contrast-take H2O in the process of photosynthesis... I don't want to make this too complicated because we haven't covered this too much yet. Okay, they take H2O and they split it and they form hydrogen and oxygen, and you know that plants give off oxygen gas. And by the way, what they do with this hydrogen is they bond it to carbon dioxide, and that's how they make their food. That's sugar, in a real small nutshell.
On the other hand, chemo-autotrophs don't use H2O. What they are going to often use is say something like this, H2S. Now, the energy that they get from breaking this up is going to actually give them hydrogen for synthesis, but it's going to give off sulfur, so they don't give off oxygen gas, but once again, you can see what they can do. They can take that and actually bond it to carbon and make other things. Chemo-autotrophs-can we have such a thing as a photo-heterotroph? Photo, this is weird; heterotroph, how bizarre. Think about this. Something that takes in food and uses light as its energy source. You bet. We can have those too, and these creatures, what they do, is they're going to take in light to literally work with the carbon that they've taken in with their food. So that's what a photo-heterotroph will be.
So look at this. We've just gone over four major modes of nutrition. We've talked about chemo-heterotrophs, chemo-autotrophs, photo-autotrophs, and photo-heterotrophs. How about this? How about a fifth one? Is there such a thing as a photo-now, think about this-a photo-chemo-auto-heterotroph? Of course there isn't. I just made that up, because how could you do all of those things at once. But now we're going to see how this energy in this trophism, if you will, is used as we start to look into the processes of respiration and photosynthesis, and you guys are going to have a great time.
Cell Biology
The Evolution of Metabolic Functions
Major Modes of Nutrition Amongst Organisms Page [1 of 2]

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