 Irrespective of time and age, whenever someone wanted to classify living things, they were absolutely confident about two groups, plants and animals. Throughout the last few centuries, somehow these two groups have remained constant. Sure, there have been a lot of changes. And I mean a lot of changes. We have removed multiple organisms from both of these groups and added them into new working terms, like algae for example. We used to think that algae were plants. Today they belong to protista. But we still have the plant and animal kingdoms with us. And they include the most complex organisms ever. In this video, we are going to dig deep and take a closer look at kingdom plantae and all that it represents today. Kingdom plantae or the plant kingdom houses, well it houses all the plants. But how do we know what a plant is? Well, from tiny mosses to giant trees, every plant is a multicellular eukaryote, which is equipped with cell walls, kind of like how fungi are, except a plant cell wall is made up of cellulose and a fungi cell wall is made up of chitin. This is actually a very characteristic difference between plants and fungi. This cellulose cell wall, which is found in plants. Plants also have chlorophyll, a pigment which plays a huge role in photosynthesis. You know the process by which plants make their own food. And all plants have chlorophylls A and B for this purpose. That means all plants are autotrophic. However, some plants also seek nutrition from other organisms, like the venous fly trap for example. It traps insects and consumes them for nutrition. Yet another characteristic thing about plants are their complex reproductive structures. Take a look at this picture right over here. This is a flower of the hibiscus plant and inside this flower you will find the reproductive structures of the plant. Now these structures, they are multicellular containers where they are kind of like multicellular containers where the gametes are produced or they are formed. Now this one right over here, this is the male reproductive structure which is going to produce the smaller motile male gametes. And the one right in the middle, this part, this is the female reproductive structure which is going to produce the much larger non-motile egg or the female gamete. The gametes will then fuse together to form a zygote which will eventually give rise to a new plant. So the female reproductive structure is made in such a way or it has evolved in such a way that it is equipped to provide nutrition to the embryo as well. Such a level of complexity is not something that you will find in other organisms like protists or fungi or any of the members of the kingdoms which come before plantae. So this is something that, this is a kind of complexity that has evolved from plants onwards and it continues to become more complicated as we move on to the other kingdoms. Which means the kingdoms that come after plantae by the way like animals for example. Oh and these extra structures that you can see which are surrounding these reproductive structures, they are composed of normal cells or rather non-reproductive cells. So the cells which you will find in this petal right over here or in this sepul right over here. So this is a sepul. The cells you will find in either of these structures they are not going to be reproductive in nature but they will be non-reproductive cells and that's why we say that these complex reproductive structures they are surrounded by non-reproductive cells. So this is what we mean by that because the petals and the sepuls which are surrounding them they are not made of gametes. You won't find any kind of reproductive cells in these structures. Now there are more plant characteristics to explore but those are more specific to a certain type of plant. So let's take a look at the different types of plants that you will find in the plant kingdom. Based on certain things like body parts, specialized tissues and seed production all plants have been categorized into four divisions. The bryophytes, the pteridophytes, the gymnosperms and the angiosperms. Let's check them out one by one. Starting off we have the simplest members of the plant kingdom, the bryophytes or division bryophyta which includes plants like mosses, liverworts and hornworts. Bryophytes are seedless, comparatively smaller plants whose bodies aren't differentiated into roots, leaves or stems for that matter. But however there are some bryophytes which show root-like, stem-like or leaf-like structures kind of like this and then there are some bryophytes which have this simple plant body which is kind of like a huge accumulation of cells like a huge blob of cells you can say and it's just one plant body which is called the thalus kind of like how you can see in the liverwort over here and this entire plant body or this thalus is attached to the substratum or the ground with the help of these thread-like structures called rhizoids. Something you can see here in this moss too. So these are rhizoids which are root-like structures. Now they may look like roots but they're not actually roots. That's what I mean by root-like or stem-like or leaf-like structures. They're not exactly the real deal. All bryophytes are so simple that they also completely lack vascular tissues. That means they have no xylem or phloem. But what do these tissues do again? Well vascular tissues are specialized tissues that can conduct food and water to the entire plant. Now bryophytes are so tiny that they don't really need this separate system of specialized tissues. They can transport these substances simply by diffusion or osmosis. But the higher bigger plants can't do that. For them diffusion or osmosis aren't just enough. So they need this entire set or this special set of tissues called vascular tissues which is going to make sure that they transport the food and water to every part of the entire plant. Next in line are the pteridophytes or division pteridophyta which includes plants like ferns, hostails, ground pines etc etc. Now they are also seedless just like the bryophytes. But unlike them, pteridophytes have vascular tissues. Moreover their bodies are differentiated into roots, stems and leaves and not just the lookalikes that we saw in bryophytes but actual roots, stems and leaves just like the higher plants. Both bryophytes and pteridophytes are often referred to as cryptogams. If you break this word down, crypto means hidden and gam which comes from gamie means to marry. So cryptogam roughly translates to hidden reproduction. But how is their reproduction hidden per se? Well these plants, the bryophytes and the pteridophytes, they reproduce via spores and spores aren't really something that we can see with our naked eye. On the other hand the plants that reproduce via seeds are called fenerogams or spermatophytes. Feneros in greek means visible. So fenerogam roughly translates to visible reproduction because we can see the seeds of a plant. Fenerogams or spermatophytes includes the gymnosperms and the angiosperms. Gymnosperms are more advanced than the pteridophytes. They have differentiated bodies, vascular tissues and like we already know, they can produce seeds. Each seed contains the growing embryo inside of it, keeping it protected and supplied with enough nutrition. In the right conditions, this seed will germinate into a new plant. But the thing about gymnosperm seeds is that the seeds themselves aren't covered with anything else. In fact, they are naked. So gymnosperms produce naked seeds. That's actually what gymno means. Gymno means naked and sperm means seed. A very popular example of gymnosperms are the pine trees. Finally, we have the angiosperms, the most complex and advanced plants of the kingdom. Angiosperms are flowering plants that produce seeds enclosed within fruits. So this is a fruit right over here. And these black dots that you see, these are the seeds. The fruit provides protection to the seeds and also helps in their dispersal. So unlike the gymnosperms, angiosperms have covered seeds. Angio meaning a container or a vessel and sperms meaning seed. So seeds within a container, kind of like that. And other than all of this, angiosperms also have very well differentiated bodies and complex vascular tissues. Those are the different types of plants that you'll find in the plant kingdom. Now these are just the very basic characteristics of these plants. If we dive into each one of these divisions separately, we're going to find out just how unique each of these plants are. And nothing is more unique than the way they reproduce. But we're going to keep that for another video.