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Current time:0:00Total duration:11:59

Video transcript

when a unicellular organism undergoes cell division are basically fission we get more cells and as a result we get brand-new individual unicellular organisms and therefore this is a method of reproduction for them however in multicellular organisms stealth cell division just gives us more cells we don't get brand-new individuals and therefore this will not work as a reproduction method for multicellular organisms and therefore in this video we're gonna focus on the reproductive methods for multicellular organisms specifically we're gonna focus on these three budding fragmentation and spore formation in the next video we'll talk about vegetative propagation in great detail and if you're wondering in a previous video we have talked about fission we've talked about binary and multiple fission in the previous video so you could feel free to when watch that if you missed that anyways so let's talk about these three and we're gonna start with budding so what's budding let's take an example to understand this take an example of a sea creature called hydra this is what it looks like under a microscope okay let me make a drawing of that here it is when this sea creature hydra which is a multicellular organism once it starts what months it is mature that is it's ready for reproduction what we will see is a tiny outgrowth from a particular part of its body this outgrowth is what we call a bud okay this process is called budding alright as time passes by we see that the bird starts growing into a tiny new baby Hydra again here's a picture to show you that here's an actual picture on the microscope you can see a new baby Hydra growing over here as a bud again let me get rid of that and then eventually this keeps on growing and growing and once it becomes big enough it gets detached from the parent body and finally we now have a brand new Hydra so this is how budding happens now an important thing to note is as this baby Hydra grows we will see it's gonna look exactly the same as its father or its mother now because there are no fathers or mothers here there's no gender over here we're just gonna call it his parent so the offspring is gonna look exactly like the parent why is that because this is an asexual reproduction there is no DNA mixing like in sexual reproduction since the DNA is going to be exactly the same we will see this will be identical to this now remember because this is an asexual reproduction that means the offspring is gonna look exactly the same as its father or mother no it is gonna call this parent because there is no gender over here so in asexual reproduction the offsprings look like clones of their parents remember that anyways some unicellular organisms can also undergo budding let me show you that before that let me just make this a little small alright okay so if you take the example of yeast then you see East also when it matures and it's ready to reproduce it grows a small bird and then that bird separates out and you get a new individual now when I first learned this I thought hey isn't budding the same thing as fission even in fission cell division is happening even this looks like cell division right well there's a big difference you see when cell division happens when fission happens one cell splits into two new offsprings all right but over here that's not happening you see a new offspring is growing from the parent and then it separates out so this is the original parent itself and this is the offspring but if this was fission when fission happens then that original cell itself divides into two new offsprings and that original parent is no longer there okay does that make sense so there's a difference between budding and fission this now brings us to the next type of reproduction called fragmentation what's that well again let's take an example let's start this time take the example of Spiro Gera Spiro Gera is basically a green algae it looks somewhat like this again under microscope and again if I take a drawing of this when Spiro Gera matures and it's ready to reproduce you know what happens to it it basically just splits into many pieces and that's the reason it's called fragmentation basically Spiro Gayla splits into many fragments and then and then each of this fragment starts growing the rest of its body and that is the cool thing about Spiro Gera it starts growing the rest of its body and as a result we now see three in this example three new Spiro grass well I think that's the proof for that okay anyways you have three new offsprings three new individuals from one that's the idea behind fragmentation and by the way this process of re growing your entire body or regrowing parts of the body this process is often called regeneration because you're regenerating parts of your body and so in this type of reproduction when the organism matures they just fragment themselves into tiny pieces and then the east each piece regenerates to grow its entire body so are there any other wonderful creatures that can do the same thing the answer is yes let me use some more examples let me make space for them ok another famous example which can do this is planaria it's a type of flat worm again when planaria matures it just sheds off its tail this part and then the two halves grow regenerate the rest of their body and then now you have to plan area another famous example is starfish even that can undergo this kind of asexual reproduction again when it matures it would just get rid of one of its arms and then this original starfish will regrow the arm and that arm will start regrowing the entire starfish and that's how we now have a new offspring now another cool thing about this is even if the didn't fragment all by themselves but if some external forces chop them into pieces let's say for example we humans go and chop them into tiny tiny pieces even in that case we will find that each piece will regenerate and grow individual bodies and it turns out some Australian fishermen founded the fount discovered this the hard way turns out that their local water bodies were infested with starfishes so they decided to just take some individual starfish and chop it off and throw it back into the ocean they thought they had killed it it turns out no you can guess what happened next each of those pieces started re growing regenerating and the population of the starfish exploded so even if you chop them into tiny pieces they can still regenerate now one thing to remember over here is even though some organisms can regenerate that's not their preferred method of reproduction for example even in the case of Hydra if you chop them up then each piece can regenerate into new individuals however Hydra doesn't do that all by itself and it's for that reason we won't say that Hydra reproduces by regeneration or or this particular method of fragmentation and regeneration the second thing to remember is that regeneration itself cannot be termed as reproduction and here's the reason why in some cases like let's say a lizard now if you chop off its tail let's say the tail comes off then this lizard can regenerate a new tail so this is regeneration but this tail cannot regenerate the entire body so in this case regeneration is happening but this is not reproduction we're not getting new individual over here so in general we will not say regeneration is the same thing as a reproduction we will say if animals or organisms prefer to fragment themselves or all by themselves when they mature and then if each one can regenerate into new individual beings whom they then will say it's reproduction lastly this brings us to spore formation the famous example for this is a fungus called bread mold again we're looking at it under the microscope over here and you might know about this if you take a piece of bread and you just leave it outside and if its moist you see a lot of fungus growing on that well that's basically this bread mold again let me make a drawing of this so here's what a bread mold would look like if you zoom in look under a microscope and the technical name for this is called the rhizopus it's a little weird name and the way I like to remember this is I see this rising part over here and I think of this as a passport even though it's not so rhizopus rhizopus helps me remember what this what the technical name is okay but let me just tell you what's the actual name of these things this rising part is called is called a high fee okay you may have to remember this for your exams this is called a high fee and this top part this - either way is not the reproductive part okay the top part this blob-like structure that you can see over here that part is the reproductive part and it's called sporangia spore and these are the only two names labels that you need to remember who here and sporangia as you can see this dotted things contain these the other things are called spores okay spores are kind of like seeds that they have the ability to grow into new rhizopus new bread more but they're not seeds we call them as spores they have very thick walls to protect them and so when this bread mold matures this sporangia will just release those spores into the air and then when the spores find a moist surface the bread knead this morning this fungus needs a moist surface to grow okay so when these fours find a moist surface they will regrow they will grow into new bread molds and that's how reproduction happens over here this is basically why moist bread will grow a fungus very fast so that's pretty much it so to quickly summarize in budding what happens well we have an outgrowth with is called AB that bird starts growing into a new individual and eventually when it's big enough it splits from its parent and we have now a new offspring in fragmentation the organisms just fragment themselves and then each fragment grows into a new part and this process is called regeneration and even if they get chopped up externally artificially by some environmental means even those fragments can still regrow but remember not all regeneration is the same thing as a reproduction as we saw in the example of the lizard and finally in spore formation the famous example of bread mold what happens is when this thing matures lots of spores are released into the air and when the spores get a moist surface this each of them can start growing into a new bread mold