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What Are Three Ways That Taxonomists Determine How to Classify Organisms?

The field of taxonomy has gone through many changes in the last few decades. In previous centuries animals and plants were classified almost entirely by their physical appearance. Now taxonomists might also look at the DNA structure to determine how closely one organism is related to another, and they might use more than one classification scheme to determine those relationships. Currently, the three major types of taxonomies are traditional, which is a straightforward comparison of characteristics; phenetic, which attempts to quantify the common characteristics; and cladistic, which bases its classification upon whether or not a common characteristic was present in a common ancestor.

Instructions

Traditional
- 1
  List the observable characteristics of the organism. This should include both physical and behavioral characteristics, and it can include DNA characteristics.
- 2
  Compare the broad characteristics of the organism with the characteristics of the various kingdoms (animal, plant and fungi, for example), and assign it to the closest matching kingdom. For example, if the organism moves, eats other organisms for nourishment and requires oxygen, it probably belongs in the animal kingdom.
- 3
  Compare the other major characteristics with those of the various phyla, and assign it to the appropriate phylum. For instance, if the animal has a backbone, it belongs in the phylum Chordata, but if it has a hard exoskeleton and no backbone, it probably belongs to Arthropoda.
- 4
  Repeat the previous step with the other characteristics of the organism to place it in an appropriate class, order, family, genus and species.
Phenetic Method
- 5
  List the physical characteristics of the organism, such as body covering (hair, feathers), presence or absence of a spinal cord and other features.
- 6
  Compare the list of characteristics of the organism with similar lists of characteristics for existing animal classifications.
- 7
  Place the organism in the kingdom, phyla, class and suborders with which it has the highest proportion of shared characteristics. For example, if an organism shares 85 percent of its characteristics with mammals but only 75 percent of its characteristics with birds, it probably belongs in the class Mammalia.
Cladistic Method
- 8
  List the physical characteristics of the organism, and compare those characteristics to the physical characteristics of ancestor organisms found in the fossil record.
- 9
  Determine which characteristics of the living organism were not present in the ancestor organism. These are derived characteristics.
- 10
  Compare the derived characteristics with those of other organisms that share the same ancestor. The organism belongs in the same group as other organisms that have the same derived characteristics that were not present in the common ancestor.

Animals & Science