Archaebacteria are the oldest life forms on Earth. Archaebacteria were first discovered in hot thermal pools and deep ocean vents, where they are able to live in boiling water. They have since been found in many other habitats. They are one-celled organisms with no nuclei. Archaebacteria are non-pathogenic. They are used in the production of bio-gas, in sewage treatment in biotechnology.
Like archaebacteria, eubacteria are complex, single-celled organisms. They are the kinds of bacteria found almost anywhere, even inside you. Some eubacteria are pathogenic. The members of this group have great significance in waste processing, biological pest control, fermented foods and scientific research.
Protists can be single-celled or multi-celled. They have membrane-bound organelles, including a true nucleus, and may have chloroplasts, so some will be green. Some protists are able to move, and some are not. Protists obtain nutrition by absorption, ingestion of other organisms and photosynthesis -- a process that converts carbon dioxide into organic compounds by using the energy from sunlight. The protist classification includes amoebae, green algae, brown algae, diatoms, euglena and slime molds.
Fungi comprise a group of single-celled or multicellular, non-motile organisms. The size of the members belonging to this group may range from small microscopic yeasts to large mushrooms. Organisms classified under fungi include molds, toadstools and mushrooms. Fungi are heterotrophs -- they derive their nutrients by absorption from materials containing organic carbon, often dead and decaying organisms.
The kingdom plantae encompasses multicellular, non-motile living organisms that have roots, stems and leaves. These organisms have cell walls and contain the photosynthetic pigment chlorophyll. Hence, they synthesize their own food through the process of photosynthesis. Organisms classified under this kingdom include algae, mosses, ferns and non-flowering and flowering plants.
The kingdom animalia is a group of multicellular motile organisms. Some organisms included in this kingdom are insects, worms, fish, reptiles, birds, amphibians and mammals. They cannot make their own food, and their mode of nutrition is by ingesting other organisms.