Agricultural Literacy Curriculum Matrix
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Good Guys or Bad Guys?
6 - 8
Three to four 45-minute sessions
Students will explore and observe microorganisms at work in decomposition as well as in the production and preservation of food. Activities include creating a "decay buffet" and identifying grocery store foods that contain or are made with the help of microorganisms.
- Fermented Foods image
- TED-Ed video The Beneficial Bacteria That Make Delicious Food
- Grocery store newspaper advertisement
- Microbe Grocery List handout
- Bread wrapper
- Label from a box of cereal
- Beef jerkey package label
- Yogurt container
- Package from dried fruit
- Food Preservation Techniques
- Quart-size Ziplocs, 1 for every 2 students
- Clear tape
- Decay buffet (including grass, vegetable peeling, straw, dry leaves, etc.)
- Soil, 1/2 cup for every 2 students
- Water mister bottle
- Food handlers gloves for each student
- Magnifying glasses
Essential Files (maps, charts, pictures, or documents)
psychrophile: a psychrophilic organism thrives at a relatively low temperature (compare to mesophile and thermophile)
decomposition: to break down or be broken down into simpler parts or substances especially by the action of living things (as bacteria and fungi)
microorganism: a living thing (as a bacterium) that can only be seen with a microscope
Did you know? (Ag Facts)
- Microorganisms can be both beneficial and harmful.
- Fermentation is a mostly anaerobic process, meaning without oxygen, carried out by microorganisms or cells.1
- Bacteria and yeasts are used in the fermentation of foods.1
- Fermentation of food has been used by humans for thousands of years as a way to preserve foods.1
Background Agricultural Connections
Interest Approach – Engagement
- Display the Fermented Foods image, which shows several food items created with the assistance of microbes.
- Allow students to begin offering ideas about what the foods pictured have in common. Use guided questions to direct them to begin thinking about how the food was processed:
- Are these foods in the same form as they were when they left the farm? (No, they have been processed)
- How are each of these foods made? (Microorganisms play a role in making all these foods; cheese, yogurt, sausage, and pickles are fermented by lactic acid producing bacteria; bread dough rises thanks to yeast, which are single-celled, microscopic fungi)
- Once students are thinking about bacteria and microbes, ask, “Is it safe to have bacteria in our food? Are bacteria always bad?”
Activity 1: Microbes in My Food
- Share the TED-Ed video The Beneficial Bacteria That Make Delicious Food (4:39 min) with your students.
- Divide the students into groups of two.
- Provide each group with a grocery store advertisement and the Microbe Grocery List handout.
- Instruct them to find all the foods in the advertisement that have a relationship to microorganisms, and write down the sale price of each item. Remember foods like ice cream may contain thickeners from microscopic algae, and foods containing dough have yeast.
- Ask each group to share the food products they found in their advertisements with the class. Did they miss any? Did other groups find the same products? Are they cheaper? Can these foods be spoiled by other microbes and make us sick?
- Explain to students that virtually all foods can spoil or be contaminated. That is why you find food additives or inhibitors or preservatives in food—to keep them fresher or viable longer.
- Read the labels of the food items listed in the materials list. Ask the following questions:
- Can you identify an ingredient that might be a food additive or preservative? Sometimes sugar, salt, or vinegar is added to a product to inhibit the growth of microorganisms. A chemical preservative may be added to do the same thing; these will have little effect on the flavor of the food. For example, jelly is so sweet that few additives need to be used to preserve freshness; the sugar acts as a “natural” preservative, the same with pickles and vinegar.
- Do all the items have the same food preservative? No, because some food additives or inhibitors only work on certain microbes, see the Food Preservation Techniques page.
- Explain to students that although we don't want our food to spoil, decomposition is an important part of the food chain. When organic materials like food waste, grass clippings, fallen leaves, and animal waste decompose, they release nutrients into the soil. These nutrients are important to growing the crops that we eat.
Activity 2: Decay Buffet
- Divide the class into pairs.
- Provide each pair of students with a Ziploc quart bag and ask them to write their names on some tape and then stick the tape on the bag.
- Set up a “decay buffet” of items like grass clippings, vegetable peelings, weeds, soil, stale bread, straw, dry leaves, etc. to be placed in the bags. In your offering of decay buffet items, try to provide twice as many dried out, high-carbon items as green, fresh, high moisture items. This mimics the recommended ratio for compost of two parts brown (dry) to two parts green (wet).
- Instruct students to place one small piece of each item at the decay buffet into their bags. Have them cut up items if necessary. Explain that it is important not to add any meat or dairy to their bags (or to compost) as potentially harmful bacteria could grow.
- Ask students to record the exact contents that they place in their bags. It may work best if one student places the items in the bag while the other records the bag's contents.
- The recorder should also note predictions as to what will happen to each item over time. Will the item rot? Smell yucky? Remain the same?
- Optional: You may want the students to switch roles and create a second compost bag with a list of contents and predictions.
- Ask the students to add about 1/2 cup of soil to their bags and to lightly mist the contents with a plant mister. (Adding a teaspoon of water and mixing the contents will work the same way.)
- Have the students blow into the bags (to inflate slightly) and carefully seal the bags.
- Once the bags are sealed, leave them for two to eight weeks. You may decide to keep the bags together or place them in various locations with differing conditions. (If you let the students choose their compost bag’s location, be sure to have everyone register their locations on a class master list or you may be unpleasantly surprised when a missing bag finally makes its presence known.)
- Have students create compost bag journals. Ask them to observe their bags periodically and record what they see happening inside. Do they see fuzzy masses? Remind students that they are not to open the bags until the designated date.
- On the designated date, have the students take their bags outside. Distribute plastic gloves to the students to wear while sorting through the contents of their bags with their partners. They may need magnifying glasses to “see” the original items. Caution: students with known allergies to mold or fungus should not participate!
- Ask students to record any items still identifiable and in their present state. Provide misters or water bowls so items can be cleaned off for closer observation and identification.
- Are any items missing? Check the list and note the items missing. How did the results compare with the predictions?
- Define and discuss the process of decomposition or decay.
- You may want to ask your students some questions:
- What are some things you have thrown away over the past couple of days? What happens to these things? Do they disappear? Decompose? Remain in the same form forever?
- Will placing the bags in various conditions have an effect on what occurs in the bags?
- Can you think of any other types of compost containers that would get the decomposition job done?
Concept Elaboration and Evaluation:
After conducting these activities, review and summarize the following key concepts:
- Cells are the basic structure of living things and many organisms are unicellular and microscopic.
- Microorganisms play an important role in decomposition, which cycles nutrients from plant and animal waste to the soil to the crops that provide us food.
- Microorganisms can be both beneficial and harmful.
- Some microorganisms help make fermented foods like cheese and vinegar. Other microorganisms contaminate food and make people sick.
We welcome your feedback! Please take a minute to tell us how to make this lesson better or to give us a few gold stars!
Bottle Biology includes plans for making a "Decomposition Column” out of 2-liter bottles. Pickling bottle “vats,” making your own microscope, and other great science projects are also included in this book.
Share the video Why Can a Cow Eat Grass with students.
Cows are ruminants. Ruminants are herbivores that have a four compartment stomach. The first stomach compartment, called the rumen, is the largest compartment and can hold over 50 gallons of food. The rumen is like a giant fermentation vat, containing billions of bacteria, anaerobic fungi, and protozoa that help to break down proteins and carbohydrates. Without these microorganisms, ruminants would be unable to digest cellulose, the fiber that makes up the bulk of plant cell walls found in grass and hay. Ruminants belch frequently to expel the build up of carbon dioxide produced by the billions of microbes in their stomach.
Ask students to make two lists—one, the good things about microorganisms, and two, the bad things about microorganisms. Ask students to add to the list and make changes as they continue to learn about microorganisms.
Try making cheese with your students! It takes a bit of time (especially if you add a bacterial culture), but your students will be able to further investigate microorganisms and their use in food, the time it takes for bacteria to make cheese, and what bacteria need to thrive and reproduce. Cheesemaking.com offers supplies and instructions for making many types of cheese.
Alternatively - have a cheese tasting party! Bring in or assign students to bring in different cheeses to sample. Create a chart that asks students to note if the cheese is sharp, mild, salty, squeaky, firm, etc. Take a class survey concerning the students’ favorite cheese. Ask students to display the results graphically.
One Bad Apple Spoils the Bunch
How did the saying “one bad apple spoils the bunch” come about? To find out take one bad (rotting) apple and one crisp, fresh apple and conduct the following test:
- Dip a sewing needle into rubbing alcohol to sterilize it.
- Pierce the rotten apple with the sterile needle. Immediately pierce the good apple with the same needle.
- Tie a string around the stem of the good apple so you can identify it later. As a control, sterilize a second needle in the same way as the first, and use it to pierce another good apple. (This apple will serve as a control in this experiment to insure that sticking an apple with a sterile needle will have no effect on the results.)
- Place the apples in a warm place and check them daily. Ask students to predict what will happen. (The apple with the string should develop a rotten spot; nothing should happen to the control apple.) The experiment demonstrates how sick people can spread germs by coughing or touching one another. If your friend has the flu, and coughs near you, it’s possible that the cough can pass the microbes (viruses or bacteria) to you and make you sick.
Suggested Companion Resources
- Food Safety from Farm to Fork: Mighty Microbes (Activity)
- Glo Germ Set (Activity)
- Little Joe (Book)
- Biotech Cheese Kit (Kit)
- Animated Life: Seeing the Invisible (Multimedia)
- Consider the Source- Cheese (Multimedia)
- Virtual Food Safety Labs (Multimedia)
- Bottle Biology (Teacher Reference)
- Antimicrobial Wash for Fresh Produce (Website)
State Standards for Utah
Grade 7: SEEd Strand 7.3Structure and Function of Life
7.3.1Plan and carry out an investigation that provides evidence that the basic structures of living things are cells. Emphasize that cells can form single-celled or multicellular organisms and that multicellular organisms are made of different types of cells.
7.3.2Develop and use a model to describe the function of a cell in living systems and the way parts of cells contribute to cell function. Emphasize the cell as a system, including the interrelating roles of the nucleus, chloroplasts, mitochondria, cell membrane, and cell wall.
Agricultural Literacy Outcomes
Food, Health, and Lifestyle
- Demonstrate safe methods for food handling, preparation, and storage in the home. (T3.6-8.a)
- Explain the benefits and disadvantages of food processing (T3.6-8.e)
Common Core Connections
Language: Anchor Standards
CCSS.ELA-LITERACY.CCRA.L.6Acquire and use accurately a range of general academic and domain-specific words and phrases sufficient for reading, writing, speaking, and listening at the college and career readiness level; demonstrate independence in gathering vocabulary knowledge when encountering an unknown term important to comprehension or expression.
MS-LS1 From Molecules to Organisms: Structures and Processes
MS-LS1-1Conduct an investigation to provide evidence that living things are made of cells; either one cell or many different numbers and types of cells.