Cladistics

In Biology, several methods are created to improve and facilitate the studies and classifications of species. Among these creations we have cladistics, which is also known as phylogenetic systematics. You will now know a little more about it and see how important it has been for Biology. Cladistics, which is also known as phylogenetic systematics, is a method of analyzing the evolutionary relationships between groups of living beings, in order to clarify their genealogy.

It is a type of biological classification school that hierarchically classifies species into groups or taxa based only on the phylogenetic principle. As you may have noticed, this is a method that classifies all living beings solely in terms of their evolutionary relationships.

The classification must be made by groups, where in these groups there will be several species that may be similar or differ greatly from the others, however, each group must be monophyletic, this means that each group must have its only ancestor and only him, all descendants came from this common ancestor who is the oldest being in the group.

Cladistics

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The creation of cladistics

This method of analysis was created by a German scholar named Willi Henning. Willi was born on April 20, 1913 in the city of Dürrhennersdorf  and even wrote a literary work that talks about cladistics, namely : Grundzüge einer Theorie der Phylogenetischen Systematik.

The book was created in 1950 in the German language, and at the time of its creation, German science did not have much prominence in the scientific scene, due to this the recognition of the work and its quality only came to light 15 years later, when the same, Henning , published a new version of the phylogenetic system, the Phylogenetic Systematics. First in German, but soon translated into English. From then on it became one of the main works, if not the main, talking about the subject. Many scholars use Henning’s book as a basis for more advanced studies in the field of biology.

The fundamental principles

The fundamental principle of cladistics starts from the premise that the species evolution relationship must be responsible for their classification. Analyzes made on ancient species, whether fossilized or still existing, look for standard characteristics that the species included in the group seem to have. They can be primitive, derived or evolved characters.

What defines an ancestral character is precisely the characteristic of living beings, be they plants or animals, which belong to the same group, all have this particular characteristic. A good example is the factor of having four limbs, a characteristic of mammals that was inherited from a common ancestor, which may be a proto-mammal or a reptile similar to a mammal. However, when we analyze an organism (micro beings), this characteristic ends up being of no use, as they have no limbs. For researchers on the topic, this type of character is called plesiomorphic and when this character is present in all the components of the group that it is part of, it is called simpleiomorphic.

If the character is derived, it is called apomorphies and if it is only part of the group to be studied it is called autapomorphies. For example, the biped factor is a characteristic of hominids and when it is not shared among other primates, it ends up receiving the name of self-morphism. And if the derived character serves to join two groups, it is called synapomorphy.

A group is defined as monophyletic when it is composed of a complex of synapomorphies, this means that this group includes all descendants of a common ancestor. A group that can be identified only by a set of plesiomorphic and apomorphic characteristics is defined as paraphyletic, that is, individuals in this group are similar in some of the descendants of a common ancestor and not all. And finally we come to the polyphyletic group, which is the one in which the members of the group are distinct and are descendants of a different ancestor.

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