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The Hidden WorldThe-Hidden-World

  • Subject:
  • |
  • Grade(s): 6-8
  • |
  • Duration: One class period

Lesson Plan Sections


Students will understand the following:
1. Much dust contains microscopic arachnids called dust mites .
2. Some people are allergic to the various proteins contained in the feces of dust mites.


For this lesson, you will need:
A computer with Internet access


1. IMPORTANT: Before beginning this activity, be sure that neither you nor anyone in your classroom is allergic to dust. You may want to send notes home asking parents to confirm that it is safe for their children to participate in an activity requiring them to handle dust.
Ask students if they have known anyone who is allergic to dust. Then explain that when people think they are allergic to dust, they are really reacting to tiny animals that live in dust, called dust mites. In fact, the actual allergen , or irritating substance, is any of a variety of proteins present in the feces of dust mites! Go on to inform students that dust mites are arachnids , animals related to spiders, and that they can be seen only under the lens of a microscope.
2. With the students, collect several types of dust in small containers. Take dust from different locations in the room, such as the backs of drawers and under tables. Turn pockets inside out and collect pocket lint also. You might use chalk dust, as well. Label the containers to show where the dust in each one was found.
3. Make a dry-mount and a wet-mount slide to view under a microscope each type of dust you find.
4. Have students view the slides and draw what they see, labeling the drawings with the locations in which the dust was found.
5. Discuss with students what they saw. Did they find any dust mites?
6. Have students use the Internet to find out more about dust mites. Ask them to list the facts they learn. Following are examples of facts students might come up with:
  • The average mattress contains about two million dust mites.
  • More than half the weight of an old pillow is accounted for by the weight of the dust mites it contains.
  • Not everyone has the same reaction to dust mite feces. Each individual reacts to different proteins in the allergen. People may not be allergic to all or any of the proteins that cause allergic reactions.
(If students do not discover the above facts, share them with the class.)

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Adaptations for Older Students:
Have students design a chart or graph that shows what was found in each sample of dust. If dust mites were found, the chart should show how many were found in each location.

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1. In the last 20 years, we have made tremendous strides in medicine and treatment of diseases. Even so, over 13 million Americans have asthma. Speculate on why deaths from asthma have risen 40% since 1977.
2. Discuss what would happen if all the dust mites in an in-service mattress were exterminated. Would bacteria or fungi or both proliferate?
3. If you were a medical researcher, what steps might you take to find the cause of allergic reactions in people?
4. NASA is very careful to clean dust particles off satellites and space probes before putting them into space. Special dust free "clean" rooms are used to outfit the craft for space flight. Explain why scientists take this precaution.
5. Describe the soil and "old-growth" trees of the Pacific Northwest in terms of size and physical makeup.
6. Explain the comparison that will be used to study the development of the old growth forest.

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You can evaluate your students on their fact lists using the following three-point rubric:
Three points: numerous facts in a well-organized list
Two points: some facts in an adequately organized list
One point: few facts in a poorly organized list
You can ask your students to contribute to the assessment rubric by determining how many facts students should find and determining criteria for a well-organized list.

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But It's Everywhere!
Mineral dust is everywhere. It comes from volcanoes, sandstorms, mining, building, and manufacturing operations. Cover a tabletop or lab area with newspaper. Have students put a few tablespoons of play sand in the middle of a piece of thin cotton cloth about 6 inches by 6 inches. Tell them to close the cloth loosely around the sand, and then hold the bag they made over a clean microscope slide and shake it for a few seconds. Students can now put the slide on a microscope stage and look at the dust that fell from the bag. Ask them to draw the mineral dust as it appears under the lens of the microscope. They should look for any particles that are geometrically shaped and try to identify them with a crystal identification book. Then they can speculate about where the sand might have come from.

Have students research arachnids. How many different kinds are there? What do they all have in common? In what ways are they different from insects? For each type of arachnid students find, have them draw a picture and label it with the common name and scientific classification. They might begin with the tiny dust mite.

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"Slime City"
Andy Coghlan, New Scientist, August 31, 1996
In the past few years, scientists have learned how to observe the inner structures of biofilms or mucilages, which are built and populated by plain, humble bacteria such as E. Coli and salmonella. New findings about the genetics and biochemistry of biofilms are reported.

"Biofilms Invade Microbiology"
Carol Potera, Science, September 27, 1996
The great recent shock in the field of microbiology is the discovery of "biofilms," or free-floating aggregations of common bacteria that create "slime cities" in water pipes or human bodies to create infection, defy antibiotics, and even kill.

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An interesting and informative site about diverse, small arthropods commonly known as dust mites.

Mites That Attack Humans
Good information on different types of mites. The diagrams are particularly helpful to students when comparing and contrasting specific species.

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Click on any of the vocabulary words below to hear them pronounced and used in a sentence.

speaker    allergic reactions
Definition: Physical symptoms, which may include sneezing, itching, and skin rashes, caused by abnormally high sensitivity to certain substances such as pollens, foods, or microorganisms.
Context: What can be a problem is the microscopic plants and animals that live in household dust: molds, mildew, fungi, and bacteria that trigger reactions.

speaker    allergen
Definition: A substance, such as pollen, that causes an allergy.
Context: There are two classes of things in dust that can be considered dangerous. First and foremost are the allergens fungal spores, dust mites, cockroaches, cat dander, dog dander and mouse urine.

speaker    aggressive sampling
Definition: Intense gathering of large sizes of random samples for examination or testing.
Context: This is called aggressive sampling. The vacuum pump sucks air through minute holes and deposits dislodged particles on the petri dish inside.

speaker    canopies
Definition: The uppermost layer in a forest, formed by the crowns of trees.
Context: Ecologist Nalini Nadkarni is a pioneer in the study of forest canopies.

speaker    epiphytes
Definition: A plant, such as a tropical orchid or staghorn fern, that grows on another plant on which it depends for mechanical support.
Context: Certain trees draw their nutrients directly from plants that hang from high branches. When these plants, called epiphytes, decompose on the tree branches, they create a layer of nitrogen rich soil.

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This lesson plan may be used to address the academic standards listed below. These standards are drawn from Content Knowledge: A Compendium of Standards and Benchmarks for K-12 Education: 2nd Edition and have been provided courtesy of theMid-continent Research for Education and Learningin Aurora, Colorado.
Grade level: 6-8
Subject area: life science
Understands the cycling of matter and flow of energy through the living environment.
Knows how matter is transferred from one organism to another repeatedly and between organisms and their physical environment; as in all material systems, the total amount of matter remains constant, even though its form and location change.

Grade level: 6-8
Subject area: life science
Knows about the diversity and unity that characterize life.
Knows that all organisms, including the human species, are part of and depend on two main global food webs: one global food web starts with microscopic ocean plants and seaweed and includes the animals that feed on them and the animals that feed on those animals; the other global food web begins with land plants and includes the animals that feed on them and so forth.

Grade level: 6-8
Subject area: life science
Understands how species depend on one another and on the environment for survival.
Knows that all organisms must be able to obtain and use resources, grow, reproduce and maintain a relatively stable internal environment while living in a constantly changing external environment; regulation of an organism's internal environment involves sensing external changes and changing physiological activities to keep within the range required to survive.

Grade level: 6-8
Subject area: life science
Understands how species depend on one another and on the environment for survival.
Knows that all species ultimately depend on one another; interactions between two types of organisms include producer/consumer, predator/prey, parasite/host and relationships that can be mutually beneficial or competitive.

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Frank Weisel, science teacher, Tilden Middle School, Gaithersburg, Maryland.

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