The history of classification systems

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History of Classification Systems

What Fits Where?





History of Classification Systems

The history of classification dates back from the 4th Century BC (Westbroek, 2000) However this article shall discuss the history of classification from the first official sorting created by Carolus Linnaeus in 1753 when he first published his book ‘Species Plantarum’ (Tutor Vista). “A practical botanist will distinguish at the first glance the plant of the different quarters of the globe and yet will be at a loss to tell by what marks he detects them.” Carolus Linnaeus stated (Carolus Linnaeus Quotes).

Linnaeus firstly divided all living organisms into Plantae and Animalia (Utah State Office of Education, 2005). However, when the first microscopic unicellular organism was discovered by Antoine van Leeuwenhoek, using his improvement on the light microscope (History of the Microscope, 2010), the current system was no longer capable of classifying all living things. Hence Ernst Haeckel proposed a third kingdom in 1866 named Protista which included Leeuwenhoek’s tiny unicellular organisms (Keo, 2011). Protista involves many organisms including algae, diatoms, dinoflagellates and so on (Heinemann, 2004).The Protista family is usually unicellular but can sometimes exist as a multicellular organism (Heinemann, 2004).

From then on, microscopes had developed and were then competent enough to observe cells that are much smaller with a clearer picture (Nobel Media, 2014). In 1925, Édouard Chatton had detected that some unicellular organisms had a distinct nucleus and some did not, which was why super kingdoms (or empires) were created. These two empires were named Eukaryota and Prokaryota. Eukaryota had a distinct nucleus and Prokaryota did not have a nucleus (Encyclopaedia Britannica, 2011). Eukaryotic cells also contain DNA within a membrane bound nucleus (Heinemann, 2004). Herbert Copeland had proposed a fourth kingdom in 1938 based on the fact that there was only one type of Prokaryota and therefore it needed its own kingdom, Monera. Monera was designed to separate organisms with and without nuclei (Jaya, 2013). Therefore, two empires and three kingdoms had been added to the original classification at this point.

1969 was when Robert Whittaker proposed a fifth kingdom, Fungi; this was for the reason that fungi was not properly established, leaping between Plantae and Monera. “Fungal cells have a cell wall composed of chitin, a substance found in the exoskeletons of arthropods that is resistant to chemical breakdown (Heinemann, 2004). During 1970’s molecular studies grew, from here, Carl Woesedecided to divide Prokaryotes into Eubacteria and Archaeobateria. Eubacteria and Archaeobateria can be differed between the habitats of their domains. Archaeobacteria are generally found in all terrestrial environments except extreme environments whilst Eubacteria can exist in all conditions. Due to this burst in molecular studies, Domains were introduced. There are now three domains; Bacteria, Archaea and Eukarya (Reece & Campbell, 2002). By the late 90’s Bacteria and Archaea had been appointed to one kingdom named Bacteria by Thomas Cavalier-Smith. The Eukaryote category is still very unclear. The current, general system is in Figure 1; however can get as complicated as Figure 2.

In conclusion, the hierarchal system of classification has gradually become increasingly complex. As technology has advanced, new discoveries have been made of nature that do not necessarily fit the old system; and hence the constant need for change. The classification system will always need to be altered as nature continues to surprise us; the current classifying system is purely based on the technology capabilities available and the range of environments scientists have been able to study.

What Fits Where?

a)Biologists have been undertaking the herculean task of classifying every species they encounter onto the phylogenetic tree. However, It can sometimes get complicated, with some animals sometimes being misclassified due to having similar attributes to other animals that ultimately are not closely related.. Even fairly recently, genetic studies have been changing the precise position of animals on the tree. However the classification system starts with the seven ranks which have basic identifying attributes which allow the biologist to quickly place a specimen into the correct domain, kingdom, phylum, class, order, genus and species (and possibly even subspecies)

This hierarchal system displayed below in figure 1 is a simplification of the actual system in practical use today. This is because as you traverse down the tree the attributes that distinguish between different classes, orders, familes etc differs depending on which domain, kingdom and phylum the species is within. . Not all spcimens fit neatly within an 8 step system, with some specimens requiring classification into ranks known as sub-; there may be subdomain, subkingdom, subphylum, subclass, suborder, subfamily, subgenus and sub species. As an example, the Platypus will be deconstructed into each of the terms as follows:

The definitions of each rank is as follows:

Domain: The highest taxonomic rank of organisms in which there are three groupings: Archaea, Bacteria and Eukarya

Kingdom: taxonomic rank that is composed of smaller groups called phyla (or divisions, in plants).

Phylum: A taxonomic rank at the level below Kingdom and above Class in biological classification, especially of animals.

Class: A group or set (of things or entities) with common characteristics, attributes, qualities or traits

Subclass: In biologic classification, a division between class and order.

Order A taxonomic rank used in classifying organisms, generally below the class, and comprised of families sharing a set of similar nature or character

Family: A taxonomic rank in the classification of organisms between genus and order.

Genus: A taxonomic category ranking used in biological classification that is below a family and above a species level, and includes group(s) of species that are structurally similar or phylogenetically related.

Species: The lowest taxonomic rank, and the most basic unit or category of biological classification.

In conclusion, the classification system can become exceedingly complex but is generally based upon a simple nd elegant structure The platypus example proved that such a simple system can help us quickly identify the key unique attributes of such a complex animal as the Platypus..

b) To examine differences between families, the two families Viperidae and Elapidae of the order Squamata and the suborder Serpentes have been chosen. Two reptile vertebrate families will be examined with reference to two distinct species:the viper and the curl snake.

The viper has an identical classification (i.e. Kingdom Animalia, Phylum Chordata, Class reptilian, Order Squamata, Suborder Serpentes) to the curl snake up until the level of family.: the viper has the family classification of Viperidae and the curl snake has a family classification of Elapidae (Rushin, 2013). The Viperidae family are all venomous snakes and have long, hollow fangs. Similarly to the Viper the Curl snake is venomous but it does however have a different coloration on its head to its body; the curl snake’s head is a darker brown or black while the body of the snake is brown (Team, 2007). The Viper’s skin is covered in a circular pattern; this helps the snake camouflage with the bushes (Klappenbach, 2014).

Figure 4

In summary, there are significant differences when classifying through the rank of families. The Venn diagram exhibits a few of the many differences between Viperidae and Elapidae families.


Two specific snakes will be compared using the information shown in the previous article; The Rattle Snake and the Malayan Pit Viper.

Both the Rattle snake and the Malayan pit Viper (MpV) fall within the Viperidae family, however their genus’s differ; one is Crotalus and the other Callesolasma, respectively. The feature that creates the Crotalus group is the rattle on the end of the tail. This group is sufficiently different to form its own group, however no subspecies are currently recognized for the MpV. Review Figure 5 for differences between these two species.

Figure 5


Rattle Snake

Malayan pit Viper





Rattle on tail

Grow below 60cm

Grow above 70cm

Found in Americas

Found in South East Asia

The system of classification has allowed scientists to agree on a process for identifying the similarities and differences between all of the various living things found. This has allowed scientists to begin to make inferences of relatedness which then allows inferences of ancestry. It is now known that whales and hippopotamuses share a relatively recent ancestor, more closely than either animal shares an ancestor with the horse. Understanding what the important differences between living things are, also allows scientists to begin to question why such differences exist. This has led to the discovery of evolution, which is the essential driver of differences between each of the types of life in existence. Scientists can also predict how foreign species are likely to adapt to a new foreign environment, which allows them to introduce new species to new environments for agriculture or for pest control. Much of this work would be much more difficult or even impossible without Linnaeus’s overarching framework for understanding the diversity of species in a systematic way.


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