Angiosperm flowering plant Life Cycle

welcome back to our series on plant diversity and evolution this is part two in our section on reproduction of seed plants we'll look at the angiosperms the flowering plants in this video we'll look at the parts of the flower pollen development egg development pollination fertilization seed development and finally fruit development so let's get to it we'll start with parts of the flower when we look at the flower we see down here we have the seil these were covering the flower when it was just bud protecting it the growing bud we have the petals we'll talk about the function of petals later we have the anther and the filament which together make the stam now this is the male structure of flower it's where pollen's produced in the middle we have this vase likee structure and at top of which is called the stigma the long thin neck is called the style and the bottom the swollen part is the ovary together these three parts make up the carpal and this is the female part of the flower now what I've drawn here is What's generically called the perfect flower it has both male and female parts some flowers might only have the female structures and other flowers only the male structures but to simplify I've just kind of done generic flower here we'll look at the male side first with pollen development in the staman if we look inside the anther we see diploid cells remember when you're looking at flowering plant you're seeing the sporify generation or the diploid generation these cells inside the anther are called microspore mother cells they're not spores they're the Mother cell to spores specifically the microspores so to become haid Spore we have to undergo meosis and inside the anther then we build microspores now if we recall our alternation generation life cycles which is the basis of all plant life cycles spores will become the gamify generation so these spores will grow by mitosis to form pollen grains remembering that the pollen grain is the male gapy in flowering plants in seed plants so if we blow one of these up and look closer here's the male gimit toy or the pollen inside the pollen there are two distinct cells the tube cell and the generative cell the tube cell will make tube through the style to the ovary to INF fertilization we'll look at that shortly and the generative cell will generate the sperm cells so this is the gapy this is not the male gamt pollen is not tree sperm it is the gight but it will be transferred from one plant to the other so here's look at the whole process of pollen development inside the anther the microspore Mother cell undergoing meosis to make the HAPO microspores the microspores developing into the pollen grain all that happening in the staman now let's get back to our flower now let's look at what's happening on the female side of things inside the carpal if we zoom in if we could look inside the ovary we would see many structures sometimes more than one sometimes just one these structures are egg producing structures they're called ovules so inside the ovary there are ovules now for Simplicity sake I'm just going to draw what happens in one OV so in an inside the ovary again there's diploid cell this is the sporify generation this is the megaspore Mother cell it's going to give rise to the megaspore so this diploid cell undergoes meosis forming Hao megaspores now most of the time all the megaspores except for one disintegrate so only one megaspore survives so there's our one megaspore the Spore will become the gight so it'll divide and it goes through three rounds of mitotic division so three nuclear divisions so our one nuclei becomes two and the two become four and the four become eight and then something very interesting happens these eight nuclei are divided into their own cell through cyto canis but we only have seven cells formed pause the video and think about what that means draw what it might look like like we have eight nuclei but only seven cells how about something like this this is what it looks like this is the female Gita fight now when we look in here let's see what we see we have this cell which I've drawn in different color to make it easy to see but that's the egg one of these haid nuclei will be the egg we have this special cell that has two haid nuclei in it and it's the endos sperm Mother cell it will give rise to the in the sperm it's an plus cell and then these other five cells these other five haid cells we call them snid which is one of my favorite words they're unimportant cells they're going to disintegrate these two included but want to draw my arrows all over the place but the snid so we have this structure inside the ovil so here's the whole side of the female reproductive structures of egg development so the megas Mother cell becomes megaspore one of them survives and divides to make this structure inside the OVU prepared for the sperm so we have pollen made in the anther and the eggs are ready inside the ovule so what do we need next we need pollination we have to get the pollen from an anther to stigma well how can that happen well wind lot of pollen is wind born and even water water can move pollen but what do we think about when we think about flowers and angiosperms the thing that's unique and different between angiosperms and gymnosperms is the use of yeah biotic vectors which is fancy way of saying pollinators living things that move pollen from one now it's time to answer question what is the evolutionary significance of petals nectar the fragrance of flowers pause the video and answer the question to attract pollinators now think about how important pollinators are to angiosperms in fact there's been co-evolution of flowers and animals to ensure or Aid this process of the plant providing some nutritional value to the animals and the animals in turn moving the pollen from one flower to another to Aid in reproduction okay so here comes the pollen lands on the stigma pollination once we have this we're ready for the next step fertilization and we're going to zoom in again to the caral and here put the pollen grain on top of it we can see the tube cell and the generative cell and we're ready for the process of fertilization we have our egg but we don't have our sperm we have pollen so this is what happens the tube cell is going to create tube down through the style to the ovary then the generative cell is going to generate two sperm that travel down the tube when they get here they're going to have double fertilization event one of the sperm is going to fuse with the egg to make the zygote The second sperm is going to fuse with the endosperm Mother cell to make tripid cell that's going to be beginning of our endosperm our nutritive tissue since there are two Fusion events we call this double fertilization this is different between the gymnosperms and angiosperms the gymnosperms we don't have this the nutritive ti tisue the endosperm is haid but in angiosperm because of this unique plus cell the Nutri tissue is triploid and it's fertilized by one of the sperms so we have double fertilization and what about all these snurds what happens to them well they just go away so now inside our Avil we have the zygote and the growing endosperm and they're going to start to grow and divide so now let's look at embryo and Seed development the zygote in the starts dividing by mitosis and the embryo has lobes of meristematic tissue called codin so we'll let the embryo start to grow the nutritive tissue around it the endosperm is triploid by the time the embryo matures the ovule becomes detached from the wall of the ovary its ingt start to thicken forming the outer seed coat so the ovil is becoming the seed the embryo the endosperm the Nutri of tissue surrounding it and the seed coat constitute the seed so the OVU is inside the ovary and the OVU becomes the seed now these are angiosperms in the video where we introduced seed plants we defined what anges sperm meant it means covered seed so here's seed and it's covered by something but in that video what did we say seeds were covered by write it down yes fruit so now we have to have fruit development let's put this back into the flower and see how the fruit develops well the ovary of the flower is going to start to swell and the Petals of the flower start to break down and start to Fall Away the ovary continues to grow the ovary becomes the fruit ovules are inside of ovaries seeds are inside of fruit and if the ovil becomes seed the ovary becomes the fruit Sometimes some of the other parts of the flower are incorporated into the fruit but there we have it the the fruit is the mature ovary now some fruits are fleshy and some are dry like acorns and pea pods but we have this question what's the function of fruit pause the video and write down what you think the answer is now lot of students will say that the function of fruit is to protect the seed but hold on think about fruit what's protective of seed if the fruit encourages you to eat it think about that and also think about other types of fruit anything with seed inside of it is fruit so pea pods the Pod itself is the fruit and the peas are the seeds peanuts the peanut this is fruit by definition and inside are seeds and we have seeds like all the nuts are are are fruit they're not the seed the seed is inside there and think about fruits like this these little sand spur that get on your shoelaces when you walk down by the beach or these which if you were an animal would catch into your fur and pull off this is fruit this is fruit and what about this each of these little dandelion things that fly off caught by the wind this is fruit inside of that little pod right there is seed so what's the function of fruit to Aid in seed dispersal to be caught by the wind or to float in the water or to even be eaten by an animal go through the digestive tract protected against the harsh enzymes and acids of the inest digestive system to be deposited somewhere else in its own little pile of fertilizer it's the aid and seed dispersal which helps the plant survive so the seeds we talked about in the in the anent seed plant video having advantage of allowing us to move into broader range of environment but flowers and fruits have evolved to Aid in reproduction of plants and to spread the seeds so that brings us to the end of our video on the antisperm reproduction if you have any questions leave them for me in the comments section below the video and hope you learn something