Taxonomy is the study of naming and defining biological organisms in order to group them together according to common characteristics. On a broader basis, the same principle can be applied to organise pretty much anything.
Timeline of Taxonomy
1500 BCE – evidence in Egypt suggests that people understood the characteristics of different species and classified them
384 – 322 BCE – Aristotle, Greece. Organisms first classified as either plants or animals. This developed with his students and beyond.
This Aristotelian system didn’t go into details with plants or fungi, they didn’t have microscopes. It was based on the idea of arranging organisms in this big chain of being. Philosophical thought began to enter this field of classification in medieval times. It was during the renaissance that this was challenged, during the Age of Enlightenment. This could be due to improvements in technology which allowed greater study using optical lenses.
1583 CE – Andrea Cesalpino classified 1500 plant species in his writing De Plantis
1682 CE – John Ray classified 18,000 plant species in his work
1700 CE – Joseph Pitton de Tournefort classified 9,000 species in 698 genera. This influenced the ‘father of taxonomy’ Carl Linnaeus.
1735 CE – Carl Linnaeus published his major works beginning the new era of taxonomy, through a structured system of classification.
Carl Linnaeus
He was born in 1707 in Sweden and was a botanist. At this time, the formal names for species was just too long winded and as more species were being discovered, it became inefficient. Carl used morphology and homology to help devise a system. Morphology is the study of form and structure of organisms. Homology is similarity of traits due to a shared ancestry.
By the time he got to his 12th edition of his work, it was 2300 pages long and he had classified 7,700 plants and 4,400 animals.
Today, we still use his basic classification system with some new things added as new discoveries have been made and technology has improved. We also use his two part naming system, binomial nomenclature, which names each species with the genus and the species in Latin. When this naming system was derived, it was expected that most people knew Latin, unlike today.
Phylogenetic Tree
Today, the classification system is known as the tree of life, or the phylogenetic tree. It allows for many branches to be added as things change with new discoveries. It is still loosely based on the Linnaean system however.
At the top sits the 3 domains: Archaea, Bacteria and Eukarya. This is based on prokaryotes and eukaryotes which evolved billions of years ago. Prokaryotes were first, single celled organisms, simple. Eukaryotes came next, which are much more complex with a nucleus and organelles. Archaea and bacteria and prokaryotes. Eukarya comprises of the entire eukaryote world which is basically, all the living organisms.
Under domains sits the kingdoms. There are 4, though one isn’t fully recognised as a kingdom by biologists. They are: Protista, Fungi, Plantae and Animalia. Protista is the one that isn’t fully recognised, this is made up of single celled organisms. Fungi is the mushrooms, moulds and other fun things. Plantae is the plants. Animalia comprises of all the animals.
Under the kingdoms are phylum. Each kingdom has numerous phylum. After this, it gets difficult to outline a strict structure. Defining features of organisms start to vary greatly leading to subphylum, clades and other types of classifications.
The traditional classification system would bring in classes after phylum. Then the orders. Then the families. Then the genus. Then the species. Again there are ‘sub’ and ‘super’ classifications in order to accommodate the large number of species that are being discovered like superfamily and subfamily.
Characteristics for Organising
There are various ways of organising organisms into groups. One of the main ways of the system is morphology which is the structure of the organism. This is generally the body plan of the organism, the structure and behaviour related to the body plan. It is evident across time that the body plan has evolved into so many different types to suit different environments. The way the organism behaves can include: how they extract energy from their environments; the method of reproduction; how they breathe; how nutrients circulate through the body; brain development and features on the body itself that develop over time. This is a short list but shows the complexity that classification faces.
This method has worked so well that even with genetic testing, the grouping of organisms according to body plan, is still fairly accurate. Species relate to each other through common ancestry and sometimes it can just be a handful of features that connect them, but nonetheless, they are connected through body plan and genetics. Modern day technology makes genetic testing more efficient than ever before along with other forms of testing when discovering fossils.
Overall, there are so many species that there isn’t one clearly universal defined system of classification. There is but there isn’t. There are some groups that are possibly not accepted by some experts and some groups that could be missing. But overall, it works for now while we only know about a couple million species. The estimate is that there at least 10 if not 100 million species of organisms. Currently, there have been around 1.5 million species of animals that have been categorised. Waiting patiently for the other few million to be discovered.
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