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Encompasses the Biological World

Eukaryotic Microbes

Distinctive features separate eukaryotic microorganisms into three categories: fungi, protozoa and algae.
Fungi:  The outstanding features that characterize most fungi are the presence of a cell wall the lack of motility and the absence of photosynthesis. Because fungi cannot derive energy from sunlight, they must depend on an external source of organic compounds to provide the energy and chemical building blocks necessary for growth and survival. Although these nutrients are usually obtained from dead organisms, some fungi can use living tissues as a food source often causing disease in the process.
Some fungi develop as single cells called yeasts, whereas others produce networks of filaments characteristic of molds. A few fungi are dimorphic existing as either yeast or a mold depending on environmental conditions. e,g. a pathogenic fungus may grow as a mold in the soil and as yeast cells in the infected human body. Another group of fungi are the macrofungi, filamentous organisms that produce the large reproductive structures familiar to everyone as mushrooms.
Fungi cause some of the most persistent and disfiguring diseases still prevalent throughout the world. Common diseases caused by fungi include ringworm infections, yeast infections of the mouth and vagina and several serious systemic diseases. Some fungi take advantage of the depressed immune system of AIDS patients and are responsible for life threatening pneumonia's. Fungi are also the source of several antibiotics, including penicillin that has saved countless lives threatened by devastating bacterial infections.
Protozoa: Protozoa are unicellular eukaryotic organisms that are generally non photosynthetic and lack a cell wall. Most protozoa are motile, moving about by the action of pseudo pods, flagella or cilia. Protozoa form an essential link in many of the earth’s food chain. Some however are responsible for widespread diseases. For example malaria is a protozoan disease that affects more people than any other infectious disease. The agents of trypanosomiasis (sleeping sickness) and amoebic dysentery are also protozoa.
Algae: Algae are a diverse group of organisms ranging from microscopic single cells to large multicellular seaweeds. They may be either motile or non motile, and most possess a cell wall. With one exception, algae are photosynthetic and are distinguished by the presence of chloroplasts within the cytoplasm. The chloroplasts are responsible for photosynthesis, the synthesis of organic material from carbon dioxide and water using sunlight as the sole energy source.

Algae are among the most important organisms on earth. They are not only the primary producers in aquatic food chains; they also generate about half of the earth atmospheric oxygen (oxygen is the byproduct of photosynthesis).
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