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Evolutionary taxonomy
Taxonomy

Taxonomy is the practice and science of classification. The word comes from the Greek language ', taxis and ', nomos .Taxonomies, or taxonomic schemes, are composed of taxonomic units known as taxa , or kinds of things that are arranged frequently in a hierarchical structure....
 or evolutionary systematics seeks to classify organism
Organism

In biology, an organism is any life thing . In at least some form, all organisms are capable of response to stimulus , reproduction, growth and developmental biology, and maintenance of homeostasis as a stable whole....
s using a combination of phylogenetic relationship and overall similarity. It differs from strict cladism where all taxa
Taxon

A taxon or taxonomic unit is a name designating an organism or a group of organisms. In biological nomenclature according to Carl Linnaeus, a taxon is assigned a taxonomic rank and can be placed at a particular level in a systematic hierarchy reflecting evolutionary relationships....
 in a classification always should include all descendants of a single ancestral node. It thus allows for paraphyletic
Paraphyly

In phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor Common descent but does not contain all the descendants of that ancestor....
 taxa. There is also a difference in the use of the word monophyletic
Monophyly

In common cladistic usage, a monophyletic group is a clade, consisting of an ancestor and all its descendants. The term is synonymous with the uncommon term holophyly....
. For evolutionary systematicists, monophyletic means that a group derives from a single common ancestor included in the group, whereas for cladists it also means that the group includes all species descended from that group.






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Evolutionary taxonomy
Taxonomy

Taxonomy is the practice and science of classification. The word comes from the Greek language ', taxis and ', nomos .Taxonomies, or taxonomic schemes, are composed of taxonomic units known as taxa , or kinds of things that are arranged frequently in a hierarchical structure....
 or evolutionary systematics seeks to classify organism
Organism

In biology, an organism is any life thing . In at least some form, all organisms are capable of response to stimulus , reproduction, growth and developmental biology, and maintenance of homeostasis as a stable whole....
s using a combination of phylogenetic relationship and overall similarity. It differs from strict cladism where all taxa
Taxon

A taxon or taxonomic unit is a name designating an organism or a group of organisms. In biological nomenclature according to Carl Linnaeus, a taxon is assigned a taxonomic rank and can be placed at a particular level in a systematic hierarchy reflecting evolutionary relationships....
 in a classification always should include all descendants of a single ancestral node. It thus allows for paraphyletic
Paraphyly

In phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor Common descent but does not contain all the descendants of that ancestor....
 taxa. There is also a difference in the use of the word monophyletic
Monophyly

In common cladistic usage, a monophyletic group is a clade, consisting of an ancestor and all its descendants. The term is synonymous with the uncommon term holophyly....
. For evolutionary systematicists, monophyletic means that a group derives from a single common ancestor included in the group, whereas for cladists it also means that the group includes all species descended from that group. The term holophyletic has been proposed for the latter meaning.

The product of evolutionary systematics is a division according to Linnean taxonomy (which can then be used to form tentative conclusions about phylogeny); the product of a cladistic classification is a cladogram, which can then be used to recommend a taxonomy.

Cladistics collects character data only from the taxa being classified; it does not consider the inferred characters of ancestors.

Evolutionary systematics also differs in method from cladistics. Cladistics involves collecting data and feeding it into a computer program. Evolutionary systematics involves a researcher following flexible guidelines which consider various kinds of evidence (which need not be represented as discrete alternatives).

Other debates between evolutionary systematists and cladists are not about the underlying approach, but on details. One is whether there is a danger of artificial classifications when preparing a classification using molecular phylogeny
Molecular phylogeny

Molecular phylogenetics, also known as molecular systematics, is the use of the structure of molecules to gain information on an organism's evolutionary relationships....
 based on only a single gene
Gene

A gene is the basic unit of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cell and pass genetic trait to offspring....
 or part of a gene. Another is whether it is sufficient to study DNA from chloroplast
Chloroplast

Chloroplasts are organelles found in plant cells and other eukaryote organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve Thermodynamic free energy in the form of Adenosine triphosphate and reduce NADP to NADPH through a complex set of processes called photosynthesis....
s, mitochondria, and ribosome
Ribosome

Ribosomes are complexes of RNA and protein that are found in all cell s. Ribosomes from bacteria, archaea and eukaryotes, the three domains of life on Earth, have significantly different structure and RNA....
s, as opposed to non-ribosomal nuclear DNA.