Archaea, Bacteria, Viruses, and Protists


Photoautotrophs - cyanobacteria



Chemoautotrophs - sulfur-loving bacteria

sulfur-loving bacteria
  • need CO2 as a carbon source
  • obtain energy not from light, but from the oxidization of H2S, HN4, or Fe+


E. coli
  • obtain their energy from organic compounds made by the photo - and chemoautortrophs


The Archaea, once thought to be nothing more than a special type of bacteria, are now known to be a very ancient lineage


Halophiles growing in salt collection ponds outside of San Francisco


Thermophiles brighten hot springs found in Yellowstone National Park


virus life cycle


Three main groups of protists:

Animal-like protists - heterotrophs

Sarcodina (ameboid) - these are either free-living or have tests (shells)

amoeba foraminerifa helizoans
An amoeba Foraminifera Helizoans

Mastigophora (flagellated) - these are frequently parasitic


Cilliaphora (cilliates) - cilliated protists


Fungal-like protists - decomposers

slime mold slime mold
  • Slime molds
    • have two stages in life cycle
      • free living (amoeboid) stage
      • plasmodial ("slug") stage
    • are often brightly colored
    • probably most closely related to sarcodina

water mold water mold
  • Water molds - closely related to true fungi
    • important marine decomposers
    • Phytophthora infestans caused Irish potato famine
    • ich, a fish-gill infestation, is also caused by a water mold

Plant-like protists - photosynthetic

euglena euglena
  • Euglenoids - flagellated, have photoreceptors, photosynthetic, autotrophic

dinoflagelate dinoflagelate dinoflagelate
  • Dinoflagelates - two flagella and a silicon test
    • cause red tides

The next two groups, the Chrysophytes and the Phaeophytes are collectively called the Chromists. They used to be placed in different divisions due to their very different morphologies, but closer inspection of their chloroplast characteristics have indicated that they are very closely related groups.

diatom diatom
  • Chrysophytes - diatoms and their relatives
    • prominent photosynthetic pigment = fucoxanthin
    • Diatom anatomy

brown algae
  • Phaeophytes (brown algae) - kelps, Sargasso
    • prominent photosynthetic pigment = fucoxanthin
    • cell walls contain algin, a common food additive used in ice cream, beer, frozen foods, toothpaste, floorwaxes, and paper (among other uses).

red algae
  • Rhodophytes (red algae) - one of the most ancient groups of eukaryotes
    • can live in very deep waters
    • cell walls contain agar, which is used as a moisture-preserving agent in baked goods and jellies

green algae
  • Chlorophytes (green algae)
    • mostly fresh water species
    • possess same pigments identical to land plants - they are their closest relative

All of the plant-like protists have different chloroplasts - therefore they are the end product of a second endosymbiosis between an aerobic (w/ mitochondria) bacteria/proto-eukaryote and a photosynthetic bacteria

Try to find where each of these groups resides on the Tree of Life presented below:

tree of life

If you have any questions or comments, please feel free to e-mail me.