To illustrate where germs exist, how they can get into and affect the body, and how the body defends itself against them.
In lower elementary school, students learn about health in a general sense; e.g., that eating a balanced diet and getting exercise and rest helps people stay healthy. They start to learn about some "things" that can hurt the body if they get into the body. Separately, they learn that germs cause some diseases. Now, they are ready to expand on this learning. They can explore how germs can get into one's body, and what the consequences could be. Also, students can begin to learn how the body physically protects itself from these germs.
This lesson explores germs, where they exist, and how they can affect the body. It also deals with a possible misconception that students of all ages may have—that factors important to health are beyond their personal control. (Benchmarks for Science Literacy, p. 346.) In learning about bacteria and germs, students will also learn about preventative measures they can take to stay healthy.
Review the student esheet, Germs and the Body, which provides students with links to the websites used in this lesson, as well as some basic instruction and the Assessment activity.
The first part of the Development instructs students to read What are Germs?, from KidsHealth. You have the option to print out the pages ahead of time and use them as handouts or have students read the text online.
For general background information on microbes, read Meet the Microbes, found at the Microbeworld website.
Where Bacteria are Found:
As directed on the Germs and the Body student esheet, students should go to Infection Detection Protection, found at the American Museum of Natural History website. Here they will play a quick game that demonstrates that bacteria, which are one type of germ, can be found everywhere—from yogurt, to soil, to air, etc.
Once students have finished the activity, ask the following questions:
- Where can bacteria be found? (Students should have picked up at least some of the following: in the air; yogurt; on a person's hands; in raw meat; in a person's mouth or stomach; in waste, soil, or contaminated water.)
- How does bacteria help the human body? (There are bacteria in the stomach that help digestion.)
- How can bacteria infect the body and interfere with normal body functions? (Remind students about the raw meat and the water. There was also an example of a girl who had hurt her knees playing soccer and she cleaned the cuts and bandaged them to keep bacteria out. Discuss with students what could happen if she did not clean and bandage her wounds.)
- How do you think too much bacteria (or other substances) in the soil, air, or water could affect humans? Explain. (Students should at least have learned from the game that contaminated water could make them sick. They probably also know that air pollution due to industry can be unhealthy for humans.)
- Are there other ways that viruses or bacteria infect (get into) the body? (You have likely discussed bacteria getting into the body via cuts, or through the mouth by drinking contaminated water or food such as raw meat. Are there other ways? Bring up the cold virus… how does that get into the body?)
What Germs Can Do to the Body:
As outlined on the esheet, have students read What are Germs?, from the KidsHealth website. Students can either read the article online or you can distribute printed copies.
Once students have completed reading the article, ask the following:
- What are some things germs can cause? (The site lists strep throat, cavities, chicken pox, pneumonia, and flu, but students may know of others.)
- What are the four major types of germs? (Bacteria, Viruses, Fungi, protozoa.)
- How do good bacteria help us? (They help us digest food, according to the site, however students may know of other "good" bacteria, such as those used to clean up oil spills. You may want to emphasize that MOST microbes are good. Unfortunately, there are enough bad ones to cause concern over human health issues.)
- How do germs affect the body? (They take the body's nutrients and could cause several symptoms, including the following: fevers, sniffles, rashes, coughing, vomiting, and diarrhea.)
- Do you think you can prevent germs from getting into the body? (This question addresses the possible misconceptions students may have about not having control over their own health. Though washing hands does not guarantee that a person will not catch something, it certainly empowers humans to take precautionary measures.)
How the Body Responds to Germs:
Also as outlined on the esheet, have students go back to Infection Detection Protection and read the Infection! section. This page describes ways that infection can occur, as well as how the body responds to microbes.
Once students are finished, discuss the following:
- Discuss the body's "first line of defense" (skin, mucous membranes, tears, etc.). Ask students what they think is going on when a defense mechanism is used. (For instance, when someone sneezes, the body is trying to "push out" something from the nose. Tears and blood help to "wash out" the eyes and wounds. The skin "keeps out" harmful germs.)
- Now discuss the body's "second line of defense" (the immune system). Students may or may not be at a level to have a good idea of how the immune system works. They should realize, however, that there are internal workings to protect the body.
Then allow some time for students to try to play Infection!. This online board game reinforces what the body's first and second lines of defense are. The game reviews in a fun manner what students have just discussed.
As directed on the esheet, students will "Create a Germ Comic Strip." In this activity, students create a comic strip that tells the story of a germ invading a human body. Students are provided with scenario ideas, outline directions, and the student sheet, What's a Germ?
You may want to review the student sheet together before starting this activity. Encourage students to be creative and fully describe the story of the germ, while emphasizing that information/facts they present should be accurate, based on what they have learned in this lesson.
Depending on your student's abilities, you may want to offer the following information in reference to the four scenarios. Older students may make the connections on their own, but lower grades may need this information in order to elaborate their stories.
- Scenario #1: the student has a cavity caused by bacteria
- Scenario #2: the student has red bumps caused by a virus (chicken pox)
- Scenario #3: the student's skin between the toes is red and itches due to a fungus (athletes foot)
- Scenario #4: the student in feeling sick because he/she drank some water containing microbes (protozoa)
Send students back to the American Museum of Natural History's Infection Detection Protection page. There are several other Web pages that address microbes, including: "Meet the Microbes," an introduction to bacteria, viruses, and protozoa; "How Lou got the Flu," a story about how the flu virus can travel over great distances; and "The Mixed up Microbe Mystery," a mystery about salmonella and an introduction to what epidemiologists do.