Growing out of the famed primordial soup some 3.5 billion years ago was the one "universal ancestor" to all life on Earth, past and present. Organisms evolved from this ancestor into many different microorganisms as well as into macroorganisms such as plants and animals. Microorganisms alive today are not more primitive than macroorganisms; they just have not evolved past the microbial stage.
Microorganisms are distinct from plants and animals in that microorganisms exist as a single cell or in cell clusters while plant and animal cells can exist only as part of a multicellular organism. By themselves these microscopic life forms are able to carry out all of their own life's processes: growth, energy generation, reproduction and maintenance. Microbial life includes all the organisms from the kindgom Prokaryotae (Monera and bacteria), and the kingdom Protoctista (algae, protozoans and slime molds as well as some microbial aquatic life) and several representatives from the kingdom Fungi (mushrooms, mold and components of lichens).
There are two basic forms of microorganisms: prokaryotic and eukaryotic. All organisms from the kingdom Prokaryotae are prokaryotes. They are generally much smaller than eukaryotes, have a non-membrane bound nucleoid of a single circular molecule of DNA and do not have separate compartments such as mitochondria or other organelles. Many are strict anaerobes (can't live in the presence of oxygen), and have simple bacterial flagella. Members of Archea and Bacteria are prokaryotic.
Microbial eukaryotes are larger cells with a membrane bound nucleus containing chromosomes and have developed compartmentalism. Examples of separate compartments are mitochondria, lysosomes, endoplasmic the endoplasmic reticulum, and food vacuoles. Eukaryotes are mostly aerobic (need the presence of oxygen to survive), and have a characteristic 9+2 undulapodia (eukaryotic flagella).
Microorganisms are the beginning, the middle and the end of many Connecticut River food webs.
The following entries are examples of some local microorganisms:
