Domain (biology) facts for kids
In biology, a domain is the highest way to group living things. Think of it as the biggest category in how scientists classify all organisms on Earth. It's even bigger than a kingdom.
Scientists group living things based on how they are related through evolution. This means looking at their DNA and how it has changed over millions of years. There are a few different ways scientists have tried to classify life into domains.
- The two-empire system divides life into two main groups: Prokaryota and Eukaryota. Prokaryotes are simple cells without a nucleus, like bacteria. Eukaryotes are more complex cells with a nucleus, like plants, animals, and fungi.
- The six-kingdom system groups life into six kingdoms: Protista, Archaebacteria, Eubacteria, Fungi, Plantae, and Animalia. This system was used before domains became widely accepted.
Contents
The Three Domains of Life
The most accepted system today is the three-domain system. It was created by a scientist named Carl Woese in 1990. This system divides all life into three main groups, or domains:
Woese looked closely at the genetic makeup of different organisms. He found that some tiny, simple organisms, which were thought to be bacteria, were actually very different. He called this new group Archaea.
What are the Three Domains?
Let's look closer at each of these three amazing domains. They represent the three main branches on the tree of life.
Bacteria Domain
The Bacteria domain includes many of the single-celled organisms you might already know. These are prokaryotes, meaning their cells do not have a nucleus or other complex parts. Bacteria are found everywhere! They live in soil, water, and even inside your body. Some bacteria can make you sick, but many are helpful. For example, some bacteria help you digest food.
Archaea Domain
The Archaea domain is also made up of prokaryotes, just like bacteria. However, Carl Woese discovered that Archaea are very different from bacteria in their genetic makeup. They are not bacteria, even though they look similar.
Archaea are famous for living in extreme environments. You can find them in hot springs, very salty lakes, or even deep-sea vents where there is no sunlight. They are often called "extremophiles" because they love extreme conditions.
Eukaryota Domain
The Eukaryota domain includes all organisms whose cells have a nucleus. This is the domain that you belong to! Eukaryotic cells are more complex than prokaryotic cells. They have many specialized parts inside them.
This domain includes a huge variety of life forms, such as:
- Animals: Like humans, dogs, birds, and fish.
- Plants: Like trees, flowers, and grasses.
- Fungi: Like mushrooms, molds, and yeasts.
- Protists: A diverse group including algae and amoebas.
Why is this Classification Important?
Understanding domains helps scientists see how all living things are related. It shows the deep evolutionary history of life on Earth. This system helps us organize the incredible diversity of organisms. It also helps us study how different life forms developed over time.
Related pages
Images for kids
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The three-domains tree and the Eocyte hypothesis (Two domains tree), 2008.
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Phylogenetic tree showing the relationship between the eukaryotes and other forms of life, 2006. Eukaryotes are colored red, archaea green, and bacteria blue.
See also
In Spanish: Dominio (biología) para niños
