History of Classification

New organisms are still being found and identified Species of organisms According to livescience.com, there is approx. 1 trillion species of organisms New organisms are still being found and identified

Aristotle divided organisms into plants & animals Early Taxonomists Aristotle is given credit for developing the first widely accepted system of biological classification Aristotle divided organisms into plants & animals Plants he classified into 3 groups, herbs, shrubs, and trees depending on the size and structure Animals were classified according to various characteristics including habitat and physical differences Aristotle’s system was not based on evolutionary history of animals

Carolus Linnaeus 1707 – 1778

18th century taxonomist Called the “Father of Taxonomy” Linnaeus’s system was based on physical and structural similarities of organisms; as a result, the groupings revealed the relationships of the organisms

Developed naming system still used today known as binomial nomenclature Binomial nomenclature is the 2-word naming system that is written in Latin Genus, which is the first word, is the group the animal belongs in (always capitalized) Specific epithet, second word, describes a characteristic of the organism (never capitalized) Binomial nomenclature made communication about certain species much easier

Binomial Nomenclature

Dichotomous Key Sometimes just having a little bit of information can help identify organisms, but it doesn’t always help you get to the answer that you want to get to Taxonomists have developed a tool called a dichotomous key to help identify organisms when there is only a little bit of information provided A dichotomous key asks a series of questions that can be answered in only 2 ways; the questions gradually help to narrow down the list of possible organisms

Example of Dichotomous Key 1a Tentacles present – Go to 2 1b Tentacles absent – Go to 3 2a Eight Tentacles – Octopus 2b More than 8 tentacles – 3 3a Tentacles hang down – go to 4 3b Tentacles upright–Sea Anemone 4a Balloon-shaped body–Jellyfish 4b Body NOT balloon-shaped - 5