Genus: Definition & Classification

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  • 0:00 Definition of Genus
  • 1:31 Use of the…
  • 3:11 Grouping Species in a Genus
  • 4:39 Lesson Summary
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Lesson Transcript
Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

What's in a name? If you're a taxonomist, a lot! This lesson will examine the classification system, focusing on the genus. It will also explain how to recognize and write scientific names.

Definition of Genus

Let's start this lesson by examining a picture. Take a moment and think about how you would sort, or classify, the organisms in this photo:

How would you organize these organisms?
animal diversity

Here are some possibilities:

  • Animals with legs and animals without legs
  • Animals with backbones and animals without backbones
  • Predatory animals and prey animals

There are scientists, called taxonomists, who work to sort or classify organisms based on similar characteristics, like you just did. This classification system is continually evolving as new species are discovered. The broadest division is domain (there are only three) and species is the most specific (we don't know how many species there are, but estimates are well over one million). Here's a breakdown of the classification system that we'll talk about in this lesson:

  • Domain
  • Kingdom
  • Phylum (plural: phyla)
  • Class
  • Order
  • Family
  • Genus (plural: genera)
  • Species

The classification of kingdom is very general and includes the animal kingdom or plant kingdom. In contrast, the division of genus is more specific as the grouping before species and after family. If you keep studying biology, it is helpful to remember the order of the classification system by using a mnemonic device, or memory tool. Dear King Phillip Came Over For Great Spaghetti is one I have used to help me remember the order of the names of divisions.

Use of the Classification System

Let's use that picture again to get a better idea of how classification works, focusing on the tiger. Here is the name for each grouping for the tiger:

  • Domain: Eukaryota (this includes everything on earth except bacteria and archaea)
  • Kingdom: Animalia (in fact, all of the critters in the photograph are in this kingdom)
  • Phylum: Chordata (of the animals, the tiger is the only vertebrate animal)
  • Class: Mammalia (this means the tiger, like you, is a mammal)
  • Order: Carnivora (the tiger is a carnivore, or a meat-eater)
  • Family: Felidae (he is a member of the cat family)
  • Genus: Panthera
  • Species: tigris

The scientific name for a tiger is Panthera tigris. There are some important things to note about scientific names that will help you in the future:

  • Genus names are always capitalized and italicized or underlined.
  • Species names are lowercase and italicized or underlined.
  • Scientific names are the genus + species

Scientific names are usually Greek or Latin and they may look like nonsense, but if you know the meaning of the Greek or Latin word, they usually make sense. For example, Panthera comes from the Greek words 'pan' which means 'all' and 'ther' which means 'prey'. Someone obviously thought that a fitting name for this genus would be 'predator of all prey'. The species name 'tigris' is thought to have originated the Persian or Iranian language and can be translated into 'an arrow with speed towards a target', probably because the tiger is a fast predator.

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