The same principle has been applied to understand the enormously diversified biological organisms, mainly animals and plants.
The lines between these terms are not very clearly drawn.
Systematics (originally: = taxonomy) aims at ordering the diversity of organisms (parts) into more general systems of taxa (wholes).
Taxonomy is the practice of recognizing, naming, and ordering taxa into a system of words consistent with any kind of relationships among taxa.
Cladistics (also known as phylogenetic systematics) is the systematic classification of groups of organisms on the basis of shared characteristics thought to derive from a common ancestor.
Phylogenetics deals with the deduction of the historical relationships between groups of organisms. It tries to represent how every life-form is related to every other life-form (see the figure below).
Taxonomy is the Science of Classifying organisms according to established rules. It can be Binomial Classification given by Sir Linnaeus or Hierarchical Classification. A taxonomic unit at any level e.g. Kingdom, Class, Order etc. is called a taxon.
Taxonomy uses Classification methods based on the characters of Species.
Systematics is the study of Biological Diversity in a evolutionary context including Taxonomy.
Cladistics involves construction of Phylogenetic trees on the basis of shared characters derived from one Ancestor.
Taxonomy is a form of classification scheme. However, taxonomy has different characteristics such as taxonomy is mostly exhaustive, semantic, and provides relationship map between the data and identify the related items or objects not only grouping them based on similarity.
In other words, the main difference between taxonomy and classification is taxonomy describes relationship in a semantic approach while classification basically groups similar items based on predefined codes.
Taxonomy was invented by Linnaeus who believed in the divine creation and immutability of species.
Cladistics is about the fundamental characteristics shared within a group but not outside the group. This shared feature came from their common ancestor.
Systematics is making trees or other represtations of evolutionary lineage relationships.
Phylogenetics is systematics based on DNA sequence comparisons and models of how one sequence Igor be related to another.
I agree with most of the other answers, but there is a particular distinction to be made. Systematics, taxonomy and phylogenetics describe fields of study. Cladistics is essentially about the method used. So phylogenies, species and other group distinctions, and the creation of a hierarchical arrangement may (or may not) use cladistics as the method of analysis. Nowadays, most people try to use cladistic methods.
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