 The diversity amongst protests has been driving scientists crazy for a very long time. However, even though there are better, more advanced ways to classify them now, generally all protests have been broadly divided into three categories. The plant-like protests, the animal-like protests and the fungus-like protests. In this video, we're going to explore the world of animal-like protests, aka the world of protozoa. Essentially, all protozoans are unicellular eukaryotes which share some similar characteristics with animals. These characteristics include things like the absence of cell walls, their heterotrophic nature and certain abilities like digesting food and moving from one place to another. While digestion is carried out with the help of something called food or digestive vacuoles, locomotion that is the whole moving from one place to another thing is carried out in a variety of different ways. Based on how they move around, protozoans have been broadly categorized into four groups. The amoebas or amyboid protozoans, the flagellated protozoans or flagellates, the ciliated protozoans or ciliates and the sporozoans. Let's start with the amoebas. Amyboid protozoans like the ones from the genus amoeba are free-living protests which are commonly found chilling in freshwater ponds and streams. A bunch of these protozoans, these amyboid protozoans, are also parasitic in nature, like in tamiba, the pathogen that causes amybic decentry in us human beings. You can identify these protozoans quite easily by the unique way they move or rather by the way they crawl. Amyboid protozoans can form something called pseudopodia, which are these temporary protrusions or extensions that arise from their cell surface. Pseudopodia, which roughly translates to false feet, Pseudo meaning false and podia meaning feet. So these pseudopodia allow amyboid protozoans to walk and capture food. But how exactly? Amybas don't have mouths or mouth-like structures. Instead, they take in food through the process or they take in food by the process of phagocytosis through anywhere on the cell surface. Now I've drawn out a very simplified version of exactly how this phagocytosis process works and how it usually looks like. So over here we have our amyba, let's mark them out. This is our amyboid protozoan amyba and this blue color dot is the food particle, food particle. So what happens during phagocytosis is that this amyba will start extending its pseudopodia towards the food particle in such a way that after a point the pseudopodia will start surrounding the food particle. Kind of something like this and it will continue to do so and once it is surrounded it will draw the food particle inside engulfing the whole thing. Once the food particle is inside the amyba it will secrete different enzymes to digest the food that it just swallowed as a whole or engulfed as a whole and this is essentially how amyboid protozoans capture food with the help of pseudopodia. Moving on to our next group we have the flagellated protozoans or flagellates. Protozoans that move around with the help of one or more whip-like structures called flagella. So in these pictures over here you can actually spot the flagella very clearly. So this is a flagellum right here and then there's one more right over here and in some flagellates these flagellates also help in gathering food other than just locomotion. Now flagellated protozoans include both parasites as well as non-parasites. Examples of parasites include giardia which is this fellow right over here so let's write it down. This is giardia and another example of a parasitic flagellate or a flagellated protozoan is this fellow right over here which is tripanosoma and both of these parasites they are known to cause diseases in humans. Giardia causes something called giardiasis which is a form of diarrhea and tripanosoma over here causes the disease sleeping sickness. Non-parasitic flagellates include the symbiotic holomastic otoidus which looks something like this. You can spot its numerous flagella all around it and this flagellated protozoan is symbiotic in nature like I said and it is found in the guts of termites. Next up we have the ciliates or ciliated protozoans. Protozoans which are identified by the presence of numerous tiny hair like structures called cilia which help in not just moving around from one place to another but they also help in gathering food. Most of these ciliated protozoans are free living and aquatic like parameshium so this is a parameshium right over here and you will find plenty of these parameshium in freshwater ponds and lakes very easily. Now the most unique thing about ciliated protozoans is the fact that they are considered to be the highest evolved ones among all the protozoans but why? That's because they have a bunch of sophisticated features that the others don't have that the other protozoans don't have. For example all ciliates take in their food through a mouth like a percher called the cytostome or the oral groove. So you can see that I have actually marked this over here in the picture so this thing right over here this is the oral groove or the cytostome and all ciliates take in their food through this mouth like structure that they have. Now no other protozoan has this feature except for some flagellated protozoans. Now once the food is inside it gets digested with the help of food vacuoles or digestive vacuoles which is something that you can see in this picture as well so these are the food vacuoles which will digest the food that this parameshium is going to eat and that food is going to enter through its oral groove or cytostome which is a mouth like a percher present in all ciliates and some flagellated protozoans. The final group on our list is that of the sporozoans which are these parasitic spore producing protozoans with no locomotory structures. Yep you heard it right sporozoans don't have any flagella or cilia or pseudopodia for that matter instead they use a very specific gliding technique to move from one place to another. All sporozoans also lack mouth or mouth like structures because they absorb all the necessary nutrients through their cell surface so no ingestion of food no mouths whatsoever. Since all sporozoans are parasites it's no surprise that some of them end up causing a variety of diseases in us humans too. One such example is that of plasmodium which is this thingy right over here in the picture so this is plasmodium the very famous malarial parasite which has been wreaking havoc all around the world so plasmodium causes malaria and those are the four different kinds of protozoans you might find chilling around you some are present right outside in the environments while some are holed up inside other organisms. Now protozoa is a group of pretty weird organisms isn't it it's their diversity is so unique and so huge no wonder the scientists are having a hard time classifying them accurately given how different and how unique all of these organisms are.