What are the Three Domains of Life?

Wednesday, February 24, 2021

 The Earth has a amazing variety of Life

Variety of Life

However all Living organisms found on Earth can be divided into three large domains based on their characteristics.

The three domains are Bacteria, Archaea, and Eukarya.

3 domains of Life

Let’s take a look at some of the characteristics of each domain.

Bacteria and Archaea are the two domains made up of only single cell organisms.

They also contain only  prokaryotes which are organisms that have cells that do not contain a nucleus nor membrane bound organelles. 

However, even though they are similar they are also very different.

First the cell walls of bacteria and archaea are different. 

Bacteria have cell walls that contain peptidoglycan.

Archaea cells do not contain peptidoglycan in their cell wall.

bacteria vs archaea

Cells have membranes that surround them and allow materials in and out and separate them from their environment.

The plasma membrane of archaea use isoprene chains instead of a fatty acid chain which are found in bacteria.

The enzymes that read the genetic code in archaea are different than the enzymes that read the genetic code in bacteria.

To date no archaea have been known to cause disease in humans and they are able to survive in extremely harsh environments like hot springs and hydrothermal vents.

The domain Eukarya contains a huge variety of living organisms.

Eukarya organisms are both unicellular and multicellular

In addition, the cells of this domain are eukaryotic cells which means they contain a nucleus and membrane bound organelles like mitochondria

The kingdoms in this domain include,

Protists, Fungi,   Plants,  and Animals

Major domains

So in summary there are three major domains used to classify all organisms on Earth.

They are Bacteria, Archaea, and Eukarya.

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