Monerans: Definition, Examples & Types

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  • 0:01 What Are Monerans?
  • 1:35 Archaea
  • 2:36 Bacteria
  • 3:24 Lesson Summary
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Lesson Transcript
Instructor: Laszlo Vass
In this lesson you'll learn about monerans, the group of organisms that bacteria belong to. Discover the name's history and the function(s) of different types of bacteria in the environment.

What Are Monerans?

Have you ever wondered about all the ways in which you interact with bacteria? It's not a topic most people think about because the word itself conjures up thoughts of disease and sickness. In reality, most bacteria we encounter are actually beneficial, not harmful.

The term Monera refers to a large group of organisms that include Archaea and Bacteria. These organisms are single-celled and lack a nucleus inside. Their DNA is loosely organized within the cell. This type of cell is known as a prokaryotic cell. As a result, bacteria are often referred to as prokaryotes.

The monerans are the original lifeforms that first developed when the earth had cooled enough and there was sufficient water to support life as we know it. They are very old. How old, you ask? 3.5 billion years (give or take one hundred million years). The monerans have survived five major extinctions, and some members live in environments where nothing else can survive.

As time has progressed and we've learned more about these original inhabitants of Earth, biologists have recognized that the category of kingdom wasn't appropriate. The Kingdom Monera consisted of bacteria and archaea, but archaea were found to be more closely related to Eukarya than Bacteria. As a result, you don't see the term 'Monera' used much anymore. Now many scientists use a three-domain system where Archaea and Bacteria are two of three domains (a domain is a step above kingdom). Monera now refers to creatures in either domain.


The name Archaea refers to age, in this case meaning 'ancient~.' This group of single-celled organisms is believed to be the original life form on Earth. This is a large and diverse domain that contains some very strange organisms. Archaea can be found in every ecosystem and environment on Earth. You will see them referred to as extremophiles, meaning they can survive and thrive in extreme environments.

Examples include:

  1. Thermophiles are archaea that live in extreme temperatures (ice caps and boiling water like the geysers and pools in Yellowstone National Park)
  2. Halophiles are archaea that live in environments with a high salt content
  3. Methanogens are archaea that give off methane as a byproduct and live in deep-sea vents and our own large intestines

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