Classifying Species
Taxonomy
•Taxonomy is the scientific study of the diversity of living organisms.
•A classification system places order and a general plan upon the immense diversity of life.
•When describing living organisms, taxonomists look for differences and similarities between them: things like their physical features, methods of reproduction and molecular sequences.
Classification systems have changed over the years. They’re fluid because as we learn more about organisms through things like DNA analysis, different species get reclassified, or entirely new taxa need to be formed. We look at this again in Unit 4.
Linnaean System of Biological Classification
Organisms were originally classified based on what they look like. Their physical or morphological differences were used to divide organisms into appropriate groups. This is called the Linnaean system of classification, as it was first developed by Swedish botanist, Carl Linnaeus (1707-1778).
Linnaeus initially intended only to give each plant a genus name and a number (Convolvulus 1, Convolvulus 2, and so on), but he soon realised that that was unsatisfactory and developed the binomial arrangement that is still used today.
His binomial system is part of a classification system that is based on large groups being divided up into progressively smaller groups by their physical characteristics. This is hierarchical rank based structure of classifying organisms, and something we still use today. A taxon (pl. taxa) is any group within a system of classification and is a collection of organisms sharing some basic features. At any level, any organism only belongs to one taxon and no other.
This system involves three domains, divided into kingdoms, phyla, classes, orders, families, genera and species. With an additional rank below species (subspecies).
This method of classification creates groups according to their similarities/ features of the groups that become more similar at each lower taxon and it allows each particular organism have its own unique scientific (binomial) name. Binomial names provide consistency worldwide as they are precise, concise and allow better communication between scientists.
It also allows biologists to recognise that that two species are closely related, e.g. Panthera leo (lion) and Panthera tigris (tiger), or Equus ferus caballus (domesticated horse) and Equus zebra (mountain zebra).
What are the rules for writing a binomial name?
Remember that this method of classification doesn’t just rely on physical features. Some organisms do not look like each other, but developments in the understanding of evolution allow us to classify based on the phylogeny of organisms, leading to evolutionary taxonomy.
For example, hyraxes are in the same clade (Paenungulata) as elephants, dugongs and manatees.
Describe four features of the Linnaean system of classification.