Constructing a Dichotomous Key

The construction of a dichotomous key is a practical referencing tool that is used to help identify species. There are billions of different kinds of living organisms in the world so to help study them and differentiate one organism from another, they are classified and named according to their similarities and differences.

 
Taxonomy is a systematic method of classifying plants and animals. By describing the appearance and other diagnostic characteristics of an organism, they can then be classified into different categories. A succession of choices is therefore written, during which, a different feature of the organism is used to identify the appropriate route through the rest of the key so that the organism can be identified. While this particular key works well in identifying this small group of specified organisms below, if a complete range of all possible species was needed then the key would have to contain much greater descriptive questions, especially when identifying the different types of species within species, that from first sight appear to be very similar. These specification would have to however be reviewed continuously as evolution takes it course, changing a species appearance and way of living in order to keep up with an ever changing environment.

 
Dichotomous keys assume a good knowledge of the subject under investigation. By applying these method it can be found discovered that dolphins and whales are in fact mammals or that a bat is not a bird just because it’s got wings. However, in most cases a particular group of organisms showing similar characteristics will follow a similar course, ie the greater degree of physical similarity, the closer the biological relationship.

 
When trying to classify an unknown organism, researchers compare similar anatomical features that appear on other species. The next step is to determine that these features are due to their evolutionary development or whether is is a descendant from their common ancestor. If it is proved to be the latter, then the two species would be classified as being biologically related in some way.

 
The two theories of taxonomy are evolutionary taxonomy and cladism (or phylogenetic systematics).

 
Classifying Animals
 
Scientists puts each living thing into seven groups (or taxons), organised from the most general to most specific. By doing this each species will fit into a particular genus, each genus will belong to a particular family with each family belonging to an order, etc.

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