The phylogenetic system is based on the principle of monophyly, which states that all members of a group must have a common ancestor that is not shared with any other group. In other words, a monophyletic group is a natural group that includes all and only the descendants of a single ancestor.
Cladistics uses a method called phylogenetic analysis to determine the evolutionary relationships among organisms. Phylogenetic analysis involves examining the shared derived characters (synapomorphies) of organisms to determine which groups are most closely related.
The phylogenetic system of classification has several advantages over traditional systems of classification. First, it is based on objective criteria, such as shared derived characters, rather than subjective criteria, such as overall similarity. Second, it provides a more accurate representation of the evolutionary relationships among organisms. Third, it is more predictive, as it allows scientists to make inferences about the characteristics and behavior of extinct organisms based on their relationships to living organisms.
Here is a simplified example of how phylogenetic analysis can be used to classify organisms:
1. Observe a group of organisms and identify their shared derived characters. For example, a group of animals may share the character of having four legs.
2. Construct a phylogenetic tree based on the shared derived characters. The phylogenetic tree shows the evolutionary relationships among the organisms, with the most closely related organisms grouped together.
3. Classify the organisms into monophyletic groups based on the phylogenetic tree. In the example above, the animals with four legs would be classified into a monophyletic group called tetrapods.
The phylogenetic system of classification is a powerful tool that has revolutionized our understanding of the evolutionary relationships among organisms. It is used by biologists in a wide variety of fields, including paleontology, ecology, and genetics.