Examples of Archaea include the methane-loving methanogens, the salt-dwelling halophiles, the heat-tolerant thermophiles and the cold-dwelling psychrophiles. These organisms live in the most extreme environments on Earth, such as extremely salty water, hot springs and deep-sea vents.
The Archaea are very similar to the bacteria that humans experience on a daily basis; however, these organisms live in regions that are hostile to other organisms. Archaeans are also prokaryotes like the bacteria because they do not have nuclei. The thermophiles live in extremely hot conditions above the boiling point of water. The psychrophiles live in cold places where the temperatures can drop to -10 degrees Celsius. The halophiles live in salty areas where the water may contain up to 9 percent salt, which is much saltier than sea water. Acidophiles and alkaliphiles live in acidic and alkaline environments, respectively.
Archaeans can live in such extreme conditions because they have adapted to their environments. These organisms often contain special substances called enzymes that can function in hostile environments. The thermophiles have membranes with special structures that allow them to tolerate high heat conditions. The halophiles, such as those living in Utah's Great Salt Lake, have pigments that allow them to convert light into energy. Their cellular structure includes adaptations that allow them to survive in salty situations. Some halophiles have sugars in their cells that counter the effects of salt water. Additionally, some halophiles feature proteins that have slightly different compositions than those in other organisms; certain amino acids, the components of proteins, have substituted other amino acids, making the proteins more resistant to the effects of salt.