Dogs actually share a domain Eukarya with the widest diversity of organisms, including plants and butterflies. At each sublevel, the organisms become more similar because they are more closely related. Historically, scientists classified organisms using physical characteristics, but as DNA technology developed, more precise phylogenies have been determined. Recent genetic analysis and other advancements have found that some earlier phylogenetic classifications do not align with the evolutionary past; therefore, changes and updates must be made as new discoveries occur.
Recall that phylogenetic trees are hypotheses and are modified as data becomes available. In addition, classification historically has focused on grouping organisms mainly by shared characteristics and does not necessarily illustrate how the various groups relate to each other from an evolutionary perspective.
For example, despite the fact that a hippopotamus resembles a pig more than a whale, the hippopotamus may be the closest living relative to the whale. Learning Objectives Describe how taxonomic classification of organisms is accomplished and detail the levels of taxonomic classification from domain to species.
Key Points Categories within taxonomic classification are arranged in increasing specificity. The most general category in taxonomic classification is domain, which is the point of origin for all species; all species belong to one of these domains: Bacteria, Archaea, and Eukarya.
Within each of the three domains, we find kingdoms, the second category within taxonomic classification, followed by subsequent categories that include phylum, class, order, family, genus, and species. At each classification category, organisms become more similar because they are more closely related.
As scientific technology advances, changes to the taxonomic classification of many species must be altered as inaccuracies in classifications are discovered and corrected.
Figure: Hierarchical models : The taxonomic classification system uses a hierarchical model to organize living organisms into increasingly specific categories.
Taxonomists tend to fall into two schools, " Evolutionary " or " traditional " systematics versus " Phylogenetic " or " cladistic " systematics. Since the s, " phylogenetic systematics " has been replacing " traditional systematics " Because the older literature and textbooks often use "evolutionary" classifications, the student must understand both systems. An unfortunate circumstance for the student is that the two schools use the same terms, but in different ways, and often refuse to recognize the alternative usage.
Evolutionary taxonomists claim to recognize only " monophyletic " taxa, but use the term to include both holophyletic and paraphyletic taxa. Phylogenetic taxonomists also claim to recognize only " monophyletic " taxa, but limit the term to what is defined above as " holophyletic ," although most reject that particular term.
This reflects a real biological difference — a species is defined as a potentially interbreeding group of organisms that can produce viable offspring that themselves can interbreed. Thus animals of two different species, like a horse and a zebra, cannot interbreed, while animals of the same species can.
Taxonomists provide unique names for species, labels that can help us find out more about them, and enable us to be sure that we are all talking about the same thing. How to Name a Species: the Taxonomic Process 1 Taxonomists begin by sorting specimens to separate sets they believe represent species.
Once the specimens are sorted the next job is to see whether or not they already have names. This may involve working through identification guides, reading descriptions written perhaps years ago, and borrowing named specimens from museums or herbaria to compare with the sample.
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