 Principles of Systematics, module 185, Phenetics and Cladestrics. In this module, we will discuss the differences between Phenetics and Cladestrics. So, what is Phenetics? Phenetics is basically a method in which we construct a phenogram. But when we are going to construct a phenogram, we consider the current state of the characters. However, the genetic characters are not considered while we are constructing the phenogram. That is, the phenogram is a pre-diagram in which we construct the current character states. In this, evolutionary characters or evolutionary history are not considered. Whereas, the cladestric approach is different. In this, we consider the current state of the characters rather than the ancestral relationships. So, this is the basic difference between Phenetics and cladestrics. In Phenetics, we consider the current character states while in cladestrics, we consider the current state as well as the ancestral relationships. Now, in organisms, the characters can be of different types. There are some characters that are deeply conserved and many characters that are not deeply conserved. Now, when we use cladestrics, when we construct a pre-diagram in cladestrics, we consider such characters that are deeply conserved. Whereas, in Phenetics, we do not consider deeply conserved characters. Now, when we construct pre-diagrams, we use three basic approaches. For example, the first approach is cladestric approach. In cladestric approach, we said that this is the approach in which we consider deep characters. In this, we consider evolutionary relationships. Whereas, in the Phenetic approach, when we draw a tree, we consider the morphological characters or the characters that are not deeply conserved. In this, we consider the current state of the characters. Whereas, the third type is molecular phylogenies. In this, we can combine both the characters. In this, we can combine phonetics and cladestric approach. In this, we use molecular data such as DNA and RNA. Now, what is the traditional taxonomy based on? It is based on Phenetics. In this, the tree diagram is not based on evolutionary relationships. Whereas, the simple morphological traits and the morphological characters are considered based on that. This technique is a faster technique and it is convenient. And in this, it is seen that there is not much accuracy in it. Whereas, the cladestric approach is comparatively slow. But in this, we can easily determine the ancestry of the organisms. Now, if we talk about Lineus, then Lineus was a scientist who believed in Phenetics. Because in this, when organisms were classified in this era, the morphological characters in that era would classify the organisms based on them. Now, when this researcher classified the organisms, he gave a framework based on its classification that the organisms in which the characters match their ancestry are the same. Whereas, if we talk about Darwin, then Darwin was a cladestric. The approach of this was that the characters in the organisms that match each other means that they are evolutionary related. They have evolved from a common ancestor. After that, when we make tree diagrams of Phenetics, it is used by different computer algorithms. On this base, which we make tree diagrams, we use distance methods in it. When we use sequence data, we use distance methods in the sequence data. Apart from that, on this base, which we use procedures, the statistical properties of it are very easily understood. After that, the chances of error in it are very low. But here, in Phenetics, when we use algorithms, use computer software and make tree diagrams, we do not have the final tree that comes with it. Because in cladestric, we make a tree diagram in cladestric. The approach of it can be different. In this, different pathways are used. Then we select the best tree from it and on its base, we find out evolutionary relationships between the organisms. So, the difference between the two terminologies is that in Phenetics, we make the current character states based on the cladestric, or tree diagrams, whereas in cladestrics, we make the current state based on the relationship between the genetic characters and the organisms.