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Autotrophs & heterotrophs (nutrition modes)

Let's explore Autotrophs, holozoic, saprotrophs & parasites. Created by Mahesh Shenoy.

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Video transcript

- Why do these plants on my balcony need sunlight? Why is this apple rotting? And why does my head itch so much? To answer this seemingly random questions we need to figure out the modes of nutrition. Basically what are the different ways of getting food. That's what we're doing in this video. So, based on how different living things get their food, we can classify them in to two categories; producers, and consumers. So, producers, as the names suggests, they are the ones who can produce their own food. Most examples involve the green trees and plants and all the green stuff around you, and some bacteria as well. And how do they make their own food? Well, they do that by using the energy of living from their surrounding. For example, plants and all the green things can use the energy from the sunlight to make their own food, and you may have heard of this process called photosynthesis which we'll talk about in more detail in future videos but, that is the reason why I need to expose these plants to sunlight, because that's from that's how they make their own food. And you and I are not producers, because we can't make our own food like that. So what are we? Well, if you're not a producer you are a consumer. Consumers as the name suggests, are the ones that consume others, that eat others for food. You and I are consumer, my friend, and most animals and insects that you are familiar with and even most bacterias, they're all consumers. Either we eat vegetables and fruits, or we eat others animals, like chicken or fish, or maybe eggs. So anyways, producers make their own food, consumers eat others. Now, before we proceed, let me tell you their biological names, right we need to give, in biology everything has a technical name, right? So, the technical name, or the biological name of producers is autotrophs. The word auto means self, and trophs mean nourish. So this means they can self-nourish, right? They can make their own food, they can feed themselves, self-nourish. On the other hand, consumers, their biological name is heterotrophs. The word hetero means others, trophs means again, nourish. So, like the name says, they can't self-nourish, they relies on others to nourish themselves. You and I and donkeys are heterotrophs. Insects and most bacterias, heterotrophs. Now, guess what? Based on how heterotrophs eat, we can further classify them in to three categories; holozoic, saprotrophs, and parasites. Again, lets look at each one in detail. Holozoic are consumers which digest their food inside of their body, you are a holozoic. I am also holozoic, most animals and insects, we are all holozoic because, we eat and then the food digested inside our body. And we are called so because, the word holo means whole, in the sense we eat whole food. Okay, what does that mean. Take an example of an apple, it doesn't say that you have to eat the whole apple, but even you take a slice of an apple, then that apple can have some constituents, right? Like, it has, for example, sugars, then it has some proteins, maybe, it also has some vitamins, and so many other constituent. These dots just represent constituents, okay? Now, when you eat this slice of apple you take in all the constituents inside your mouth, right? That's that's the whole that's the meaning of whole. That's the meaning holo, you're eating this whole thing. And then, once it goes into your body then, your digestion system breaks it into it's constituent particles, right? That's the whole idea behind holozoic. These are are the animals that digest their food inside their body. Now in order to be a holozoic, you need to have pretty good digestion system so that you can break down whatever you eat inside your body. But, what if you don't have a good digestion system, Then what happens? Well, then you become a saprotroph. Saprotrophs are the ones that don't have a good digestions system, and as a result, they digest the food outside of their body, and then eat it. And as we will see, it's these guys who are responsible for rotting and decaying things, and they include most bacteria and mushrooms, well, mushrooms is a very specific example. In general, these are fungus, right? So, bacteria and fungi, fungi is plural, fungus is singular, so, bacteria and fungi are the saprotrophs, they digest the food outside of their body. And they're there everywhere, okay? I mean, if you take that piece of apple, and let's just leave it outside, don't eat it, then, pretty soon you find these bacteria and fungi will start attacking it, so, let's say these bacteria start attacking it, now, since they can not digest the food inside their body, because they don't have a very good digestion system, what they do is they try to digest the food outside. How do they do that? They spit all the enzymes, or the acids needed to break down the food, right? So, as they spit these enzymes and acid, chemical reactions take place, and the food gets digested then and there. And so this apple start getting broken into it's constituents and then, once it's broken, then these bacteria will start absorbing these constituents. Okay but, why does it rot and start smelling? Well, that's because, whenever digestion is happening, whenever chemical reactions are happening, some byproduct is created, right? And it's these byproducts that start making things rot. And that's what makes the whole thing smell as well, and because of that, more insects get attracted, and now you can't eat this. And this sounds very disgusting, right? But what's interesting is, a similar digestion process happening in our bellies as well, even when we digest food, all this stuff happening but, because it's inside our body, we don't smell it but, if you throw up, if you vomit then, you can smell it, I know it's pretty disgusting, sorry for that. But, when you vomit basically, you are vomiting out digested food with all these byproducts, and you know, even that smells, right? So, we digest the food inside but, these saprotrophs digest the food outside, and that causes things to rot, and that's the same reason why this apple is rotting, it's being digested by these saprotrophs. Another example is, you may have seen, if you keep bread outside for some time, then they will start growing this fungus over here. The fungus are digesting it outside now, and your teeth also gets decayed for the same reason, There are a lot of bacteria in our mouth, and when we eat food, the food gets stuck in the teeth, and then, they start getting digested by the saprotrophs. And that's why I always brush my teeth twice every day. And, just a small thing, okay? After learning this, I used to feel they are so annoying. I mean, if they were not there, I wouldn't have to brush my teeth, things wouldn't rot at all, wouldn't that be awesome? No, because, guess what? They also feed on the dead, they are the ones that make sure to decompose all the dead stuff, right? So, if they were not there, then all the dead things like, the dead animal and plants and everything would just pile up, you can not imagine what earth would be. So, thanks to them, they decompose all the dead stuff as well and recycle all the nutrients, make sure they go back into the nature, which can be re-absorbed by the plants, re-used to make more food, they are super essential for our environment. And the word sapro itself means rotting, that's why they're called saprotrophs because, they eat on the dead, and decay, and make them rot. Okay, and finally, what if you can't digest food at all, Whether inside or outside, then what? Then, you become a parasite. Parasites hardly digest any food. Then how do they get their nutrients? Well, they depend on a host, meaning another living organism. For example, this leech is a parasite, it gets stuck to my leg, let's say, and then it starts sucking my blood. Now, my blood already contains digested food, and so, it just starts getting nutrients from my blood directly. So you see, they don't have to digest anything, so, in that case, since they are depending on me, I am their host. Similarly, my head is scratch, I have to scratch my head so much because there are some parasites on my head. Lices are examples of parasites as well, they also suck on the blood from the scalp, again, I am their host. So parasites can either live on the surface of their hosts, like leeches and lices, or they can live inside them as well. For example, tapeworms and roundworms live inside intestines. So, even though you may be healthy, you have these inside you intestines, okay? And guess why are they there? Well, because again, intestine where most food already digested, and so, they can just eat that. And so, the word para kind of means alongside, in the sense that eating alongside it's host, so, whatever I eat, they goes to these guys as well. Now, an important about parasites is I should think they're trying to kill me but, no, they are not trying to kill me, they want me to be alive so that I can keep on feeding them for their entire life. So, parasites don't try to kill their hosts but, they end up harming their hosts. For example, when this leech starts sucking on my blood, they rupture the skin, because of these lices, I am getting, my head is getting itchy, tapeworms and roundworms can cause my stomach to ache. So they are definitely no trying to kill us but, they end up harming us. And again, I should think parasites are pretty useless, and many scientists usually think as well but, recently we realize, even they are useful. For example, some scientists believe that the worms in our intestines actually help in boosting our immunity over there. Another example, some leeches are useful in removing infected blood from our body, and would you be surprised if I told you that fifty percent of all the species of living things on our planet are parasites? That's right, there are a lot of parasites on our planet. Almost every living thing has a parasite inside, or on top of it. Anyways, that's pretty much it so, let's quickly look at what we learned. There are two basic kinds of living beings; autotrophs, who generate the food themselves using the energy from the surrounding, and the heterotrophs, who can't produce their own food so they eat others, and based on how we digest the food, heterotrophs can be further classified as holozoic, if you take the whole food inside, and digest it inside your body, most animals and insects come under this category, and you need a pretty good digestion system for that. But, if you don't have a great digest system, no worries, you become a saphrotrope, then you just digest the food outside of your body, and then you must make things rot, they are the decomposers, they are the ones who eat on the dead and the decaying animals, most bacteria and fungi. And finally, if you can't even do that, then you just become a parasite, just stick yourself to a host or live inside of them, and then you get free digested food. They might harm you but, most of them have no intentions of killing you.