 The phylum Arthropoda is very successful in terms of how the numbers go. They constitute greater than 80% of all known animal species. In a previous video we have looked at their general characteristics and the different types of respiratory organs that different members have. In this video we will look at their sense organs, again they have a variety of them, and their excretory system. So in their sense organs, one of the most important organ is the same as ours, the eye. And some of them have a simple eye which works very similar to ours. So this is a simple eye. There is one cornea, one lens, the light ray just goes in and forms an image at the back of the eye. There are many arthropods which have a more complicated eye and it's called a compound eye. As you can see there are all these little units in the eye and each of these units forms a separate image. So if you look at the eye diagram, each of these is a separate unit forming a separate image. So each of the blue things that you see is a lens and each of the lenses they send their separate sets of rays into the back of the eye and then many different images are formed by each of these components. So this is called a compound eye and the image that it forms is a mosaic. It's very different from the image that we typically see. We see one image which is very clear. These guys on the other hand see an image which looks like a mosaic. That's because all the images from the different parts are kept side by side. Another important sense organ that they have is the antenna. You see this grasshopper over here and you see these yellow things. These are its Antony, singular antenna. So this is also a sense organ in different arthropods. It has different functions. The commonest of functions that Antony have is the sensation of touch. Of course it can touch and feel different objects. Then it can also smell and taste different things. Another very interesting sense organ that arthropods have is the statusist. This is an organ of balance. So you see this ball over here. This is a solid mineral mass which moves. Whenever the organism moves, the ball moves a bit. It's heavy but it still moves a bit and then presses on. You see these little hair like structures, it presses on them and those hair like structures are connected to these nerve fibers. So whenever the ball presses on any of these hairs, that information is sent to the brain of the arthropod through these nerves and the arthropod can gauge whether it is upright or tilted a little bit and then readjust this posture to regain balance. The last thing that I'm going to talk about in this video is the excretory system of arthropods. The excretory system consists of the Malpegian tibials. So the pink things are the Malpegian tibials. Don't get intimidated by the name. It's just named after the scientist who discovered it, Malpegi, he was the name of the scientist, hence the name. And what is this purple structure? It is nothing but the gut. So it's the digestive tract and what happens is the excretory matter is formed inside the Malpegian tibials or starts forming inside the Malpegian tibials and then finally it's deposited inside the gut, which is uric acid. So uric acid is the nitrogenous waste in many arthropods and both digestive waste and nitrogenous waste that is the digestive system and the excretory system, both of them have the same outlet. This is all about phylum arthropoda.