Lesson Plan

Microorganisms of the Desert

Mature soil crust nurtures seedlings.
Mature soil crust nurtures seedlings.

NPS photo by Neal Herbert

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Grade Level:
Sixth Grade
Biology: Animals, Biology: Plants
30 minutes
Group Size:
Up to 36
National/State Standards:
Utah State Science Core Curriculum Topic, Standard Five: Students will understand that microorganisms range from simple to complex, are found almost everywhere, and are both helpful and harmful.
algae, Fungi, microorganism, bacteria, Biological Soil Crust, lichen, desert pothole


This outdoor lesson plan includes three hour-long investigations: discovering pothole dwellers, examining lichens, and investigating biological soil crusts. In the classroom, students examine photographs of common microorganisms and use microscopes to search for organisms in pothole water.


Mystery Photographs

a. Define the term microorganism.
b. Name at least two kinds of microorganisms and their functions.

Life in a Pothole

a. Identify at least three species of animals in a pothole.
b. Explain at least one reason why diversity is beneficial to a pothole ecosystem.

Lichens Up Close

a. Identify rock lichens and name two lichen components.
b. Name one role of lichens in the high desert ecosystem.
c. Explain the basic steps of the scientific process.

Cryptos Up Close

a. Identify cryptobiotic soil.
b. Name at least two functions or roles of cryptobiotic soil in the high desert ecosystem.
c. Explain the basic steps of the scientific process.
d. Measure and record cryptobiotic soil crust data.

Exploring Pothole Microorganisms

a. Make a slide, and use a microscope properly.
b. Explain the basic steps of the scientific process.


Microorganisms are everywhere and play many important roles in the high desert ecosystem. Some microorganisms are plants or animals, but some belong to the other three kingdoms of living things. Some sixth-grade students may be familiar with the kingdoms and may ask about them, so here’s an update or review.

1) Monera consists of bacteria, including cyanobacteria. Monerans are small, simple, single cells, and sometimes form chains or mats. Some absorb food; some are photosynthetic.

2) Protista includes protozoans and algae of various types. These are large, complex, single cells, sometimes forming chains or colonies. They get their nutrition in a variety of ways.

3) Fungi are molds and mushrooms. These have a multicellular filamentous form with specialized complex cells. They absorb food.

4) Plantae are plants, including mosses, ferns, woody plants, and non-woody plants. These are multicellular forms with specialized complex cells; they photosynthesize.

5) Animalia includes everything from sponges and worms to mammals. Animals are multicellular forms with specialized complex cells. They ingest food.

Viruses aren’t included in the kingdoms becausethey are on the borderline between living and non-living things. They are noncellular parasites that cannot live or reproduce outside of a living organism.

Probably, the most fragile component of this arid region is cryptobiotic soil crust. The crust is a community of microorganisms, including cyanobacteria and a variable mix of lichens, fungi, and mosses. This network of organisms plays a vital role in erosion control, nitrogen fixing, and moisture absorption. One footprint can destroy years or even decades of this soil’s growth, and new growth often has a different mix of organisms than that of the previous crust.

Rock lichen is composed of another community of microorganisms, namely fungi, with algae, cyanobacteria, or both. That’s two or three kingdoms intermeshed. Fungus forms the tough outer layers of lichen, while algal (and/or cyanobacterial) cells enmeshed in fungal threads compose the inner layers. The lichen structure is more elaborate and durable than either fungi or algae alone. Dry lichens have the ability to absorb more than their own weight of water. They can carry on food production at any temperature above 32ºF. Temporary water, such as dew, can be taken almost directly into the algal cells of the lichen; the water does not need to go through roots and stems as it does in vascular plants.

Desert potholes provide homes to a fascinating array of small organisms and microorganisms. Pothole dwellers have unique adaptations, enabling them to survive in this feast or famine environment. Most of these organisms have shortened life cycles, reducing the length of time they are dependent on water, and thus allowing them to live in shallow, short-lived pools. The life cycles of clam shrimp and fairy shrimp are 5-10 days. The life cycle of a tadpole shrimp is 12-14 days. Tadpole shrimp, as a result, require deeper potholes in order to survive.

A pothole’s size determines its diversity and species make-up. Microorganisms, such as single-celled algae and protozoans, inhabit shallower pools. Slightly deeper pools might have tiny worm-like larvae of midges wriggling around their bottoms. The deepest and largest pools might contain a variety of tiny crustaceans and insects: fairy shrimp, clam shrimp, tadpole shrimp, water striders, back swimmers, water boatmen, and whirligig beetles.

A pothole is a unique habitat that is very easily disturbed. Pothole organisms are sensitive to sudden water chemistry changes (brought on by sunscreen, for example), temperature changes, sediment input, being squashed, and being splashed out onto dry land.



Lichens Up Close

Have students “advertise” in a newspaper article the use of lichens in a new household product or a technological breakthrough. The advertisements must include basic lichen information and their important role in an ecosystem.


Additional Resources

Ahmadjian, V. (1989). Lichens are more important than you think. BioScience 45: 164.

Belnap, J., & Gardner, J.S. (1993). Soil microstructure in soils of the Colorado Plateau. Great Basin Naturalist 53: 40-46.

Brady, Irene. (1998). The redrock canyon explorer. Talent, OR: Nature Works.

Canyonlands National Park. (1988). Pothole Point interpretive trail guide. Brochure.

Corbridge, J. & Weber, W. (1998). A rocky mountain lichen primer. Niwot, CO: University Press of Colorado.

Graham, T. B. (1999-2000). Life in the fast pool. Plateau Journal (Winter): 29-45.

Johnston, R. (1997). Introduction to microbiotic crusts. U.S. Department of Agriculture, Natural Resources Conservation Service, Soil Quality Institute, Grazing Lands Technology Institute (July).

Kuhn, D. (1988). The hidden life of the pond. New York, NY: Crown Publishers.

Nardo, D. (1991). Germs: Mysterious microorganisms. The Encyclopedia of Discovery and Invention. San Diego, CA: Lucent Books.

Reid, G. (1967). Pond life: A golden guide. New York, NY: Western Publishing, Golden Press.

Ricciuti, E. R. (Ed. Vincent Marteka). (1994). Microorganisms: The unseen world. Woodbridge, CT: Blackbirch Press.

Sharnoff , S. D. (1997). Lichens: More than meets the eye. National Geographic (February): 58-71.