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KINGDOM: MONERA* (BACTERIA)

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general information | cyanobacteria

Bacteria are set apart from all other organisims because their cells lack nuclei (they are prokaryotic). All other organisims are eukaryotic, meaning that their cells contain nuclei. Because of this fundamental difference, all prokaryotes have long been grouped together in one Kingdom, Monera. However, strong new evidence indicates that there are actually two distinct groups of prokaryotes: Bacteria (or Eubacteria) and Archaea (or Archaebacteria). These two groups diverged from one another near the time of the origin of life! The eukaryotes almost certainly evolved from the eubacteria shortly thereafter. Because of this new information, the taxonomy of the prokaryotes is in transition, and "Monera" will most likely be replaced by two new Kingdoms in the near future: Kingdom Eubacteria and Kingdom Archaea. [* The term "Monera" is used on this page only because it is likely to linger in textbooks for a few years.]

Bacteria are the oldest life forms on earth, dating back about 3.8 billion years. (For reference, the earth is about 4.6 billion years old. The human family only began to emergy about 3 million years ago.) Bacteria are ubiquitous, occurring at amazingly high densities in water and soil (and milk left out over night!). Most people are familiar with disease-causing bacteria, but these organisims have many other important functions in nature. They are important decomposers. And many herbivores, such as cows and termites, rely on bacteria in the digestive tract to break down plant material. (For more information about bacteria and animal digestion, see The Animal Pavilion at Digital Learning Center's Microbe Zoo.) Phytosynthetic bacteria are called cyanobacteria, or blue-green algae, and form some interesting symbiotic relationships with other species. For example, lichens are a symbiotic relationship between a fungus and a cyanobacterium or a green alga.

Bacteria have more versatility in their metabolisms than any other group of organisims. Many species are "chemoautotrophic," meaning they live off chemicals in their surroundings-not food or light. No other organisims can do this! Some of these chemoautotrophs metabolize sulfur around hot thermal vents in the depths of the ocean, forming the base of the foodchain in the only ecosystem we know which does NOT depend on the sun for energy! For more information, check out Life Without Light: Discoveries from the Abyss, Deep Sea Vents, or Deep Sea Hydrothermal Vents (under construction).

Bacteria are also the only creatures on earth which can take nitrogen from the atmosphere and attach, or "fix" it, to other atoms and molecules. Green plants need these nitrogen compounds in the soil to survive- they can not use the gaseous form of nitrogen in the air. Thus, "nitrogen-fixing" bacteria are a crucial link in the nitrogen cycle- one that all other organisims depend on. Members of one family of plants, the legumes, form special symbiotic relationships with nitrogen-fixing bacteria in the soil. For more on nitrogen fixing, try Nitrogen Fixing Microbes, Nitrogen Fixing Plants?, or Molecular Basis of Symbiotic Plant-Microbe Interactions (very technical).

General Bacteria Information

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Cyanobacteria

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KINGDOM: PROTISTA or PROTOCTISTA (PROTISTS)

Skip the introduction and jump to the protist links:
general information | images | algae, plankton, and seaweed | slime molds | protozoa

The protists are an odd lot. They are lumped together in one kingdom because nobody knows what else to do with them. All protists are (supposed to be): 1) eukaryotic and 2) unicellular. While they are all eukaryotic, they aren't all unicellular. The algae in particular often occur in multicellular forms. Most of these are quite small, but some get to be rather large such as seaweed and kelp.

The various groups of protists are almost certainly not close cousins evolutionarily speaking. They are often placed into three groups based on their method of obtaining energy. Fungus-like protists absorb food from their surroundings. Plant-like protists (algae) are photsynthetic. And animal-like protists (protozoa) engulf food particles (i.e. eat). These three groups probably have more in common with the kingdoms Fungi, Plantae, and Animalia, respectively, than they do with one another. But it is very difficult to determine an accurate phylogeny for these little critters-especially because some, like the genus Euglena, both eat AND conduct photosynthes. So for now, they remain one big, artificial "family."

Fungus-like protists known as slime molds are fascinating organisms, often studied for their unusual life cycle. Microscopic algae in the plankton form the base of most aquatic food chains, assuming the role that green plants play on land. Protozoa are important players in plankton communities.

General Protist Information

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Protist Images

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Algae, Plankton, and Seaweed

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Slime Molds

  • Internet Guide to Myxomycetes (slime molds)
    Biology, distribution, ecology, collection, classification, and more! Be sure to stop by the Ecology of Myxomycetes page. Ecology is an aspect of slime molds we don't usually hear much about!
  • Dictyostelium WWW Server (cellular slime molds)
    "The purpose of this site is to facilitate communication between researchers involved in studies of Dictyostelium discoideum, Polysphondylium and similar organisms."
  • Introduction to Slime the Molds
    Berkely Phylogeny of Life site.
  • Poems by Bill: Slime Mold
    No, I'm not kidding. A poem about slime mold. I don't understand this poem, but then I again, I don't understand most poetry. Nevertheless, I just HAD to include this link!

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Protozoa

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