What are some key characteristics of Archaea?

The key characteristic of Archaea that sets them apart from other domains of life is the presence of unique membrane lipids. Archaea have a distinct type of lipid in their cell membranes, which includes ether linkages rather than ester linkages found in the membranes of Bacteria and Eukarya. This unique composition allows Archaea to survive in extreme environments, such as high temperatures, acidity, or salinity, as their membranes are more stable under harsh conditions.

The unique membrane lipids include branched-chain hydrocarbons and are often found in the form of monolayers or bilayers depending on the environmental conditions, which further enhances their adaptability. This characteristic is essential for distinguishing Archaea from other life forms and plays a crucial role in their ecology, physiology, and evolutionary significance.

The other characteristics mentioned do not accurately reflect Archaea. They do not possess peptidoglycan, their cellular structure is not similar to plants, and while some Archaea can be pathogenic, the majority are not known to cause diseases.