Rotten But Not Forgotten

Lesson Overview:

National Science Education Standards:

Content Standard F: Science in Personal and Social Perspectives
Population, Resources, and Environments

Strand 2: Knowledge of Environmental Processes and Systems
2.1: The Earth as a Physical System

Key Concepts:

1. The process of decomposition involves changes in matter.

2. Microbes that enhance decomposition are found in the air, water and soil.

Objectives:

Students will:

design and conduct investigations to identify the effect that temperature, soil, water and air have on the process of decomposition.

observe and record the effect of decomposers on several types of organic matter.

develop graphic representations of data collected during the investigations.

Cross-Curricular Connections:

Language Arts:
• Record and organize information, discuss experimental design, and share results.

Mathematics:
• Construct graphs and other representations of data collected during investigations.

Social Studies:
• Discuss how the process of decomposition affects their everyday lives.
• Practice group consensus in making decisions.

Observing
Communicating
Comparing
Investigating
Inferring
Applying

Materials:

Per Student
• Research Journals
Per Group
• Minimum of 4 disposable petri dishes, labeled according to contents
• Garden soil
• Spray bottle filled with water (rainwater, or pond water; preferably not treated water)
• Small pieces of fruit, vegetables, bread
• Other types of materials determined by students
• Hand lenses
• Microscopes
• Measurement tools
• Thermometer
• Chart paper
• Markers

One introductory class period and one final class period, with daily 5 minute observations/recordings; expected completion within approximately 3-4 weeks.

Procedure:

1. Describe the purpose of the investigation (to determine the effect temperature, water, soil and air have on the rate of decomposition) and elicit student input in designing investigations that allow for cross class comparisons of data. Collecting and analyzing the data is a key component, so students should set guidelines on how to structure data collection.
   
2. Students determine the best methods for the investigations, get approval to proceed, and prepare petri dishes according to established class criteria. How will the measurement of decomposition be determined? Will mass be considered? How should the investigation be carried out? For example, each group of four may choose one type of food to investigate and set up petri dishes as follows: Each dish would have the same type and amount of food, but the medium would be different. Dish 1 may contain only the food with exposure to the air, Dish 2 only the soil and food, Dish 3 soil, water, and food, while Dish 4 may have only water and food. Temperature, keeping the dishes sealed or unsealing them periodically to add water, etc., are other considerations. There are numerous ways this investigation could be designed that would provide information, and it is important that the students are given the opportunity to determine the variables and work through the process.
   
3. Students predict and record what will happen to the food in the dishes and set the dishes aside in the same general area of the classroom where they would be exposed to the conditions congruent to their designs.
   
4. Students follow their procedures, observe the dishes and record their observations on the data collection table over a specified period of time.
   
5. Students analyze their data, graphically represent their findings, and present the information to the class.
   
6. Use the students' information to lead the discussion to bring closure to the activity and develop the concept of decomposition and its effects:
   What changes were observed during the investigation? Why do you think these changes have occurred? Which food began changing first? Which took the longest to decompose? Were there any differences in the decomposition rates of the food in the various dishes? What were the variables? Were all of the dishes and food exposed to air at some point? Would that make a difference in the rate of decomposition? Did temperature effect the rate of decomposition? What are some reasons for the differences in decomposition rates? Is any food still recognizable? Were you able to draw reasonable conclusions based on the data you collected?
   
7. Properly dispose of petri dishes.

Suggested Discussion Questions:

Do you think there may have been a better way to design your investigation? What might you have done differently?

How does this investigation relate to you in your life?

Have you ever thought about what happens to leaves that fall off trees or trees that fall in the forest? What about the bodies of dead animals? Do they just lie where they fall forever?

What do you think decomposition of matter does to the composition of soil?

What are some ways to inhibit/encourage decay?

Further Investigations:

Investigate the contents of a rotting log — one that has been on the ground for a period of time — and determine what kinds of processes have been taking place. Locate and identify any "critters" that may be present. Discuss the chemical and physical decay processes that are taking place.

Interview the school cafeteria staff to determine how they handle food to inhibit decay.

Determine ways decay of matter affects health, i.e., tooth decay, gangrene, etc.

Determine ways decay of matter is beneficial, i.e., disposing of harmful materials, composting to divert waste from the landfill, etc.

Research food preservation methods and their effectiveness in inhibiting decay, i.e., refrigeration, drying, canning, etc.

Market Research Analyst
Regulatory Affairs Specialist
Manufacturing Engineer
Environmental Engineer
Food Service Manager
Waste Management Engineer

Assessment Procedures:

Investigations should be monitored and judged according to a rubric produced, in part, with student input.

Design a home or school composting program.