Micro organisms comprise heterogeneous group of organisms with a common microscopic size, quick growth and reproduction and wide geographic dissemination. They can't see with eye because they are smaller then 0.1 mm.
Although big variety of these organisms is provocative of obstacles in their classification, they can divide on three groups:
- prokaryotes (bacteria and cyan-bacteria),
- eukaryotes (alga, funguses and protozoa)
Bacteria- comprise heterogeneous group of organisms with prokaryotes matter of cells. They can divide on gram-positive and gram-negative bacteria.
Alga- is micro organisms which have cells with chlorophyll. Different colour of alga can explain with a fact, that beside chlorophyll they have also other pigments in their cells.
Funguses- are micro organisms which have in their basis mycelium.
Protozoa- are organism of animal origin. In this group are amoeba, foraminifera, radiolarians, paramecium etc.
Viruses- are the smallest and the simplest micro organisms, intracellular parasite, because they don't have cell structure. They attack bacteria (bacteriofag), plants (herbal viruses), animals (animal viruses procure leukaemia, benign and malignant tumours).