hi everybody and welcome back today we are going to be looking at torrido fights or phones and this is the next step in our plant diversity series of videos and just remember if you go back a video you should be able to see our bryophyte video and every video i'm going to recap the alternation of generations just because it's so important to know all the terminology that goes along with it so moving into doritos fights they are our next step in our plant diversity and essentially they're a little bit more evolved than our bryophytes our moss they have a lot more qualities which make them better to survive on the surface of the earth they're better terrestrial plants and let's go through some of the characteristics they have and some things that they still lack so we've stepped up in our complexity and now we can see that choreophytes have a vascular tissue which means that they have xylem and phloem it makes them able to grow bigger and a little bit stronger they do have a cuticle which means it prevents them from drying out however it's not a very thick cuticle which means that ferns and other territories often grow in shadier cooler places because a lot of direct sunlight may dry them out they still however rely on water to reproduce but because they have vascular tissue we now can say that they have leaves and true stems but they still have rhizoids which if you remember are similar to roots and rhizoids purpose is to anchor our plants onto the surface they're growing on i'm now going to recap alternation of generations if you've already watched the previous video you don't need to watch this bit and you can fast forward through to the life cycle stage but if you haven't watched it let me recap very quickly so the alternation of generations refers to how plants alternate between a sporophyte and a gametophyte sporophyte generations make spores gametophyte generations make gametes another easy way to tell the difference is that sporophyte often refers to the time in which the plant is growing and getting bigger whereas the gametophyte generation is the time at which the plant is making gametes and is trying to reproduce and there are some very important terms we need to remember starting off with haploid and diploid when we alternate between generations we alternate between these two ideas so when something is diploid like we see over here diploid essentially means that it's dye it means two you have a full set or a full pair of your chromosomes whereas haploid on the other hand is half essentially you've gone through a process where you have half the number of chromosomes that you have why would you want to do that because you want to make gametes remember you're going to take an egg cell and a sperm cell and you're going to put them together so when you plus those two chromosome numbers together you want them to equal the original amount and that brings you to some other words we must be familiar with the word meiosis is in reference to the process where we make gametes and that yet again is when you take a full set of chromosomes let's say you had 24 and you're going to go through meiosis and you're going to half it and it will become 12. and that's because later on you'll take 12 from a sperm cell 12 from an egg cell combine them together to make the 24 again when we refer to mitosis this is for growth this is slightly different in that you are going to take a cell that has 24 chromosomes but you want to keep that number exactly the same and so in mitosis 24 will remain as 24 chromosomes there'll be no chromosome change the next word a set of words that we need to be familiar with is our sporophyte and gametophyte and so the word sporophyte simply refers to the structure that is making the spores and the other is the gametophyte which is referring to the structure that makes gametes and in the alternation of generations plants are either sporophytes or they're using their gametophytes they're two different structures and in order to understand alternation of generations we need to know that we will have a female side to this diagram which is represented on this side i'm just going to draw the female sign and then on this side we have the male side of our diagram and essentially this is what we need to do we need to take some cells from our sporophyte in this case we call it the megasporophyte because it's big and it's the female structure which is always bigger and we're going to take a couple of those cells as you see here circled we are going to go through meiosis which means we're going to half the chromosome number and we're going to make a mega spool that megaspore is going to grow and develop and it's going to produce what we call the archiclona the archiconum is the equivalent of the ovary and what's going to happen is inside that archegonium we are going to produce egg cells now they're ready in the equivalent in the males we are going to look at the microsporophyte which is the slightly smaller sporophyte and we're going to go through meiosis and we're going to make microspores now one of these microspores is going to keep on developing inside of the antheridium which is the equivalent to the testes it's where we would produce our sperm cells in plants and now we have our sperm and our egg our gametes and if they come together and they fuse through fertilization they produce a zygote that zygote can then grow into either a male or a female and we start the whole process all over again so unlike bryophytes or moss plants where we normally start our life cycle journey with the gametophytes or the other plant cycles i'm going to begin with the sporophyte generation the reason for that is when you look at infern you are looking at a sporophyte you can't actually see the gametophyte and so i'm just going to zoom in on that part of the life cycle so it's a little bit bigger and clearer for us to look at and so we begin our journey here at the mature sporophyte which as we note is deployed remember has a full set of chromosomes now if we look on the underside of our ferns sometimes you will notice that there are these little black brown sometimes yellowy orange structures and they are called sorry sorry are where we actually have our reproductive structures developing and they're going to go through meiosis so if we were to zoom in on one of these sorry we would see the following things so if i go in a little bit closer and i'm going to zoom in on just one of these small little spots we would find one of these that's a story and inside the story are sporangium and there is one two three four on the side and four on the other side and that's where we're going to make spores and how do we do that we go through meiosis so that means on this side of the family we are going to start off as 2n diploid we are going to go through meiosis and we are going to become in haploid where does this take place inside of these really small little specks called the sorry so this whole thing that i've got a box around is called a sorry and inside that story we get these sporangium and and that's what i've highlighted here and there are now eight if i highlight all of them inside there will be cells they will undergo meiosis and they will produce our spores those spores are released and now they land on the ground and when they land on the ground they are going to grow into our gametophytes now what's unusual about ferns gametophytes if i zoom in a little bit closer to this picture so we can see it here is that they don't have two separate uh male and female gametophytes like we saw in bryophytes they were like two separate plant structures in our churritophytes in our phones they're actually just one structure and it's this whole heart shaped structure and this structure is called a prothalis and on the surface of this little heart-shaped prothalis we will find the male and female reproductive organs in this case you must remember the antheridium is the male and our archegonium is our female and they're on the same structure they're just slightly separated from one another and so if we were to zoom in on them and have a look on the inside they are sort of a u or a cup shape and that's so that we can trap our water in there and so what happens is inside of our male uh antheridium we're going to make our sperm cells and inside of our female we're going to make our ovules or our eggs and yet again water is very important in ferns we are going to wash the sperm cells into the female archegonium and we're going to have fertilization which if we remember is when we take n plus n because it's a sperm cell plus an egg cell and that makes a 2 n zygote now our diploid zygote is going to go through mitosis it's going to grow it's get bigger and what we do is if we zoom out a little bit there is our gametophyte remember there is our our prothalis is our little heart shaped structure and growing out of the topic is our sporophyte it's a little baby sporophyte and as that sporophyte gets bigger and bigger if we zoom out now so that we can look at the full cycle once more let me bring this up here we are going to start our journey once more with all of our mature sporophytes producing our spores on the undersides of its leaf if you remember we made those in the story and we start the whole cycle again and that is why we call it a alternation of generations you alternate between the diploid sporophyte generation and the haploid gametophyte generation right let's end off this lesson with our terminology recap so we looked at our alternation of generations into reader fights where you alternate between the sporophyte generation if you're making spores which is the adult plant or gametophytes which is where you are producing gametes or eggs or sperm cells we looked at meiosis which is the process of halfing your genetic information your dna or your chromosomes it's where you make gametes whereas mitosis is just where you replicate the cells and make more of them and you maintain how many chromosomes you have we spoke about diploid amount of chromosomes which is a full set 2 in or haploid which is half the noun the amount then we looked at the specific life cycle of phones and we spoke about those tiny little dots on the underside of the leaf it's called sauri inside of those story are a sporangium sporangium are the structures that are going to produce our spores and those spores are haploid those haploid cells are going to land on the ground and they are going to grow a pro phallus which was that heart shaped structure on the surface of that prothalis we are going to find the antheridium which is the male reproductive structures the akigona or okigonim which is the female reproductive structures sperm cell are washed over to the female orcagona where the eggs are they're fertilized and they produce a diploid zygote that diploid zygote undergoes mitosis it grows bigger and bigger and bigger out of the gametophyte until you can't actually see the gametophyte anymore when you look at a phone you only see the sporophyte and we start the whole life cycle again thanks for listening everybody i hope you enjoyed the lesson i will see you again soon bye