Classification of Living Organisms

Scientists believe that there are over 10 million different kinds of life forms or species on Earth. In order to make the job of scientists easier, they classify living things into groups, based on how they are the same, and how they are different. To classify means to group ideas, information or objects based on their similarities. The science of classifying is called taxonomy.  Classification is an important part of your life. In taxonomy, a kingdom is the first and largest category. The kingdoms represent very large groups of life forms that are all similar in some ways, but can be very different from one another in other ways.

More than 2,000 years ago, Aristotle was among the first to document the division of life forms into animals and plants. Aristotle classified animals according to observation, for example, he defined high-level groups of animals by whether or not they had red blood (this roughly reflects the division between vertebrates and invertebrates used today). But Aristotle’s method of classification failed to grasp the significance of evolution. His methods were based on traditional views of species, including philosophical ideas that added to the confusion. Carolus Linnaeus, a Swedish physician and naturalist, developed a system of taxonomy much of which is still used today. He gave each organism a simpler, unique name.

Linnaean system was called binomial nomenclature; it gives a two-word name to every organism. The two-word name is commonly called the organism’s scientific name. The first name is the genus, second is the specific name. A genus is a group of different organisms that have similar characteristics. The genus name and the specific name make up the scientific name of a particular species. A species is the smallest, most precise classification category. Linnaean system uses Latin, because when he developed it, Latin was the language used by the universities and understood by all. In this system no two organisms have the same scientific name.

Phylogeny of an organism is its evolutionary history or how it has changed over time. It tells the scientists who the ancestors of an organism were. The classification separates the organisms into six kingdoms.Most taxonomists today divide the six-kingdom system into groups called domains.

  • Animal
  • Plant
  • Fungi
  • Protists
  • Eubacteria
  • Archaebacteria

Each organism is placed into a Kingdom. Then it is assigned to a phylum. In plant kingdom we use division instead of phylum. Phylum is divided into classes, classes are divided into order, and orders are separated into families. A genus is a group within a family. A genus can have one or more species.

  1. Kingdom
  2. Phylum
  3. Classes
  4. Order
  5. Families
  6. Genus
  7. Species

    Importance of Scientific names:

  1. They help scientists avoid errors in communications.
  2. Organisms with similar evolutionary histories are classified together.
  3. Scientific names give descriptive information about the species.
  4. Scientific names allow information about organisms to be organized, found easily and efficiently.

Most field guides have descriptions, illustrations of organisms, and information about habitats to help with identification.

A dichotomous key is a detailed list of characteristics used to identify organisms and includes scientific names. Dichotomous keys are arranged in steps with two descriptive statements at each step. To use the key you must always begin with a choice from the first pair of descriptions. The end of each description is either the name of each species or directions to go to another step. If you use the dichotomous key properly, you will always end up with the correct name for your species.     Keys are useful in a variety of ways.