[Music] hi my name is andy welcome to med school eu and now we're on to the new topic in our biology section for the imat which is called reproduction and inheritance and the first subject that we're going to talk about in this topic is called life cycles so the life cycles of all organisms are going to fall under one of the three categories there's going to be the diploid life cycle which is the animal life cycle is the same thing and there's going to be the alternating generation so between diploid and haploid life cycles as well as the haploid dominant life cycle that will exist in a lot of fungi and algae so the first thing is we're going to talk about the animal life cycle and this one we have discussed previously we've talked about this in the process of meiosis and mitosis however we're going to go over it again since this topic comes up more specifically in this section so here what we have what we begin with is a zygote so here let's label this as a zygote and zygotes are simply fertilized cells that have the egg and the sperm fertilize the sperm fertilizes the egg and it becomes a zygote which is a diploid structure so this is already diploid to end this is a diploid structure and zygote is going to undergo many many mitosis processes in order to become a fully grown adult or fully grown animal or a human as it is as i showed here so this this part of the life cycle will be called the diploid diploid so anything past the process of fertilization as you can see here fertilization as soon as fertilization happens the sperm and the egg join together we create a zygote and this entire process the this life cycle of a human or an animal is going to be diploid phase so we basically will have two pairs of full sets of chromosomes and over here we're going to undergo lots of mitosis in order to produce our fully sized human and the germ cells of a fully grown mature animal will undergo meiosis so somatic cells which are regular body cells will continue to undergo mitosis and they're not going to produce gametes however germ cells are going to undergo meiosis which are sex cells and meiosis will actually produce cells that enter into the haploid phase and haploid is simply one copy of chromosomes so here we have the if we're talking about humans over here we have 46 chromosomes or 23 pairs or we could say 23 pairs as we typically say because they're homologous pairs they're the same just there's two pairs of each one from the mother one from the father and here we have just the 23 chromosomes in total on on the gametes so of course these are gametes we already know that so the production of gametes uh through meiosis this enters into the haploid stage and why we call animals life cycles diploid dominant because most of our life we spend in the diploid phase we most of our life cycle is spent being deployed with 46 chromosomes the only time we have 23 chromosomes or one single set of chromosomes is going to be when we are gametes pretty much so before fertilization and after meiosis is the stage of haploid which is a very tiny small stage of the animal life cycle this is why we are deployed dominant now let's take a look at another type of life cycle and this one would specifically pertain to plants and some fungi and algae and this one will be alternative generations so let's let's label this as all terminating generations because it's it's equally under going to undergo the diploid and the haploid within its life cycle this is why i have the division here completely square and equal so what we have is the again we're going to begin here with the fertilization so the sperm in the egg join fertilization occurs and of course here we have the diploid phase so we can label this as diploid with 2n and what happens is we have our zygote so same as humans pretty much we undergo mitosis and we produce a structure that is called a sporophyte sporophyte and that's the structure that is typically labeled as the diploid phase of a plant and the sporophyte will then undergo some of its cells will undergo germ cells would undergo meiosis and which the meiosis would then produce spores so these are spores and spores are going to be haploid at this point so we can label this as the haploid with just a single set of chromosomes so now we know that spores are going to be haploid and these spores will undergo mitosis further and they will produce something called a gametophyte so let's label this as gametophyte which and a gametophyte will will be a structure that is also in the haploid phase and then from the gametophyte it's going to produce our gametes so we have the egg and the sperm we could say gametes these gametes will then combine to to go through the process of fertilization and produce a zygote and the whole cycle begins all over again now the very important thing to notice the big difference between plant and some other fungi and algae their life cycles compared to the animal life cycles is that in the plant in this alternating generations life cycles we are going to have mitosis mitosis and both and and to end so we're going to have mitosis in haploid and mitosis and diploid as you can see mitosis happens here in the haploid stage however in animal life cycles we don't have mitosis in the haploid stage we simply undergo meiosis we produce our gametes and they fertilize we do not have any growth occurring of the gametes so that's the important uh distinction between plant and some other fungi and algae compared to the animal life cycles and finally we're going to take a look at the other fungi and algae and this one's going to be called haploid dominant so let's label that haploid dominant so completely the opposite of animal life cycles and here of course we can label as diploid and as you can see diploid is a smaller part of the life cycle here we have the haploid and let's let's go through this so again begin with fertilization we get our zygote the zygote will grow and undergo the process of meiosis which will then produce spores spores which will be haploid at this point and these spores will undergo mitosis to produce a gametophyte so this is gametophyte and gametophyte is a haploid stage of the the life cycle of these of the fungi and algae and now from the gametophyte it's going to undergo mitosis again in order to produce gametes and these gametes will be of course one male one female which will then go through fertilization and the whole life cycle will begin again but as you can see because it undergoes mitosis twice here most of the time the fungi are seen in their gametophyte form right here and this gametophyte form is actually haploid they don't have their their two sets of chromosomes they don't have the pairs of chromosomes these haploid gametophytes as we see them existing in nature because most of the time they're spent being in this sort of form they are going to be in their haploid phase most of their life cycle which in contrast to the animal life cycles it's completely the opposite so this concludes our lecture on life cycles now we're actually going to skip over sexual and asexual reproduction because that is something that we talked about in the cell as the basis of life topic so here we talked about binary fission of prokaryotes we talked about mitosis and meiosis of of eukaryotes and there's no need to go through the same sexual and asexual reproduction and in terms of reproduction and inheritance topic so next we're actually going to take a look at genetics and the first topic of genetics will be mandalay in genetics which will constitute his gregor mendel's laws and their applications [Music] you