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Life Science: Session 2

Classifying Living Things: The Domain Archaea

What features distinguish archaea from other life forms?

Thermal vents, home of
some Archaea

The domain Archaea contains many organisms that are not very well characterized. Archaeans are prokaryotic, single-celled organisms. Their cells have a cell wall, but it is not made of the same substances found in the cell walls of plants, fungi, and bacteria. Despite lacking the organelles and nuclei seen in eukaryotic cells, the archaea are actually not that similar to bacteria. In fact, based on their DNA and various fundamental cell processes, they are more closely related to eukaryotic organisms.

Most archaea do not make their own food. Many absorb their food sources, in a similar way to bacteria. Archaeans that do make their own food do not make it through photosynthesis — that is, using carbon dioxide, water, and the sun’s energy. They may use other sources of carbon found in the environment, and chemicals for energy rather than light.

How are archaea important to people?

Archaea were initially discovered in extreme, inhospitable environments like hot springs and deep-sea hydrothermal vents. We now know they occur in a diversity of environments, including cow guts, where they produce methane, and many aquatic ecosystems. Techniques in molecular biology are revealing a striking diversity of archaea in many habitats. Unlocking the mystery of what they are and how they are transforming their environment is proving to be a very exciting challenge for microbiologists.

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