Artificial, Natural and Phylogenetic Classification in Biology with Examples

 Difference between Natural, Artificial and Phylogenetic Classification

Classification is the systematic grouping of organisms based on their similarities and differences (or shared common characters).

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Artificial Classification

• Based on random selection of unifying or shared characteristics
• Classification system based on a few easily observable traits
• Unrelated organisms may be placed together, related organisms may be separated
• Advantage: Stable, easy to develop
• Disadvantage: does not show evolutionary relationships, very rigid without flexibility.
• Examples: Theophrastus (370-285 B.C.) classification of plants into herbs, shrubs and trees
• Linnaeus (1707-1778): Classified flowering plants based on number and arrangement of stamens
• Aristotle Classified animals into “with blood “and without blood”

Natural Classification

• Classification based on several similarities between organisms, and evolutionary relationships
• Several morphological characters, anatomy, cytology, biochemistry, genetics, ontogeny are considered for classification
• Related organisms placed together; unrelated organisms separated
• Adanson (1727-1806), A.P. de Candolle (1778-1841), Bentham (1800-1884) and Hooker (1817-1911)
• Advantage: Classifies organisms based on similarities, widely accepted classification system because
• Disadvantage: Shows evolutionary relationship to some extent. Rapid mutation of parameters can cause contradictory classifications; sometime closely related groups may be placed separately
• Example: Adanson (1727-1806), A.P. de Candolle (1778-1841) classification of plants,
• Bentham (1800-1884) and Hooker (1817-1911) system: Classified over 97,205 plant species into 202 families and 7,569 genera primarily based on morphological, anatomical and floral characters.

Phylogenetic Classification

• Based on Evolutionary ancestry and genetic relationships
• A classification primarily based on molecular data especially DNA sequences from multiple genes
• Organisms are classified based on evolutionary ancestry
• Advantage: This molecular data allows for a more reliable classification that reflects evolutionary lineage and common ancestry. Depicts genetic relationships, a modern system of classification
• Disadvantage: Difficult to classify based on evolutionary tendencies due to imperfect fossil records and DNA sequencing possible only in sophisticated laboratories therefore not widely accepted as natural system of classification.
• Examples: Engler (1844-1930) and Prantl (1849-1893), Bessey (1845-1915), Hutchinson (1884-1972), Takhtajan (1910-2009), Cronquist (1919-1992)
• Angiosperm phylogeny Group (APG IV) Groups angiosperms into 64 major clades, a classification that reflects evolutionary lineage and common ancestry.