The Three Domains

Domain Bacteria:
Domain Bacteria consists of prokaryotic unicellular organisms that can be either beneficial or pathogenic. The organisms classified under this domain can live almost anywhere. Most are motile via flagellum or type IV pili. They reproduce asexually through binary fission and have no nervous system. Some organisms under this domain are heterotrophic, meaning that it derives its nutrition from organic substances, while other organsims in this domain are autotrophic, meaning that the organism can take organic substances and form inorganic substances that it will use as its nutrition. Organisms under this domain contain peptidoglycan in their cell walls and may be one of three shapes. Bacterium may be round, known as a coccus, shaped like a capsule, known as a bacillus, or it may be a spiral, known as spirillum.

Domain Archaea:
Domain Archaea is made up of prokaryotic organisms that live in extreme environments and are known as extremeophiles. There are four groups of extremeophiles; methanogens, extreme halophiles, thermophiles and members of the genus Thermoplasm. Methanogens can not grow where there is oxygen and they produce methane which could be the smell of a swamp. Extreme halophiles live in places like the Great Salt Lake, very salty environments. Thermophiles live in very hot places that could be as hot as 105 degrees Celsius. For example, a thermal vent could be the perfect place for a thermophile. Lastly, members of the genus Thermoplasm, can be found in coal deposits due to the acidic and hot environment. These organisms lack peptidoglycan in their cell walls and nervous systems. They move by using flagella and cilia, unless they are non-motile. Archeans can receive nutrition in three different ways. They can be phototrophs and obtain energy and nutrition by sunlight. A second way is by being lithotrophs, which means they obtain energy and nutrition from inorganic compounds. Lastly, they can be organotrophs and obtain energy and nutrition from organic compounds. These organisms reproduce asexually by binary fission, budding, or fragmentation.

Brief description of the three domains