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Decomposers | Goals

General Unit Information

For students who have studied Plants and Animals, the most important idea to learn from the Decomposers unit is this: The answers to the Matter and Energy Questions are essentially the same for animals and decomposers. This will be a surprising conclusion, because students generally view decay as an entirely different process from animals eating and moving! What students need to learn from the Decomposers unit is that the Movement Question is different for decomposers and animals: decomposers digest food outside their bodies, then move small organic molecules through their bodies for biosynthesis (growth) and cellular respiration (energy for growth and functioning). Students already know the answers to the Matter Change Question and the Energy Question from studying Animals. So, in this unit students just need to learn how to apply their knowledge to different organisms that are a lot more like animals than they thought!

Unit Goals

The tables below show goals for this unit in two forms. Table 1 shows unit learning objectives aligned with inquiry and application practices. Table 1 also contrasts the goal performance with performances of students at lower learning progression levels.

This table is followed by a list of Next Generation Science Standards (NGSS) addressed by this unit.

Type of Objective

Learning Objective

Challenges for Level 2 Students

Challenges for Level 3 Students

Inquiry: Measurement

3. Planning and carrying out investigations

4. Analyzing and interpreting data

5. Using mathematics and computational thinking

8. Obtaining, evaluating, and communicating information

Measure mass changes in molding bread and other materials.

Detect changes in CO2 concentration in chambers with decaying materials.

Level 2 students may have trouble reading digital balances and attaching meaning to measurements in small fractions of grams.

Level 2 students will not think of air as a mixture of different gases, so while they can understand that BTB detects carbon dioxide, they will not think of carbon dioxide as one of the mix of gases in the air.

Level 3 students may have trouble accounting for tare mass and interpreting small fluctuations in readings on digital balances.  They will have difficulty identifying threats to accuracy and precision in measurement.

Inquiry: Arguments from evidence

2. Developing and using models

3. Planning and carrying out investigations

4. Analyzing and interpreting data

5. Using mathematics and computational thinking

6. Constructing explanations

7. Engaging in argument from evidence

8. Obtaining, evaluating, and communicating information

Construct arguments that use evidence about changes in mass of decaying materials and carbon dioxide concentration to defend claims about movements of atoms and chemical changes during decay.

Level 2 students will not interpret changes in mass as evidence of movements of atoms, believing instead that materials “break down” or are destroyed when they decay. Level 2 students are also likely to be unaware that gases are involved in the decay process.

Level 3 students will see the relevance of evidence to claims, but they will not systematically consider alternate hypotheses or show how evidence supports or refutes specific claims.

Inquiry: Collective validation

3. Planning and carrying out investigations

4. Analyzing and interpreting data

5. Using mathematics and computational thinking

7. Engaging in argument from evidence

8. Obtaining, evaluating, and communicating information

Find patterns in data collected by multiple groups about changes in mass of decaying materials and carbon dioxide concentration.

Level 2 students may focus primarily on their own results rather than seeing the value of multiple measurements.

Level 3 students will understand that multiple measurements are valuable, but they will have few strategies for finding patterns across multiple trials.

Application: Matter Movement question

2. Developing and using models

6. Constructing explanations

7. Engaging in argument from evidence

8. Obtaining, evaluating, and communicating information

Describe systems and processes in fungi in a hierarchy of scales, including atomic-molecular and macroscopic scales.

Draw and explain movements of materials during 1) growth of fungi and 2) function/ movement of an organism, including oxygen and food entering fungal cells, and carbondioxide and water vapor leaving fungus.

Level 2 students will explain decay as a natural process in which dead things disappear or are recycled.  They will not interpret mass loss as evidence that atoms are moving.  They will understand that decomposers are agents of decay, but not that decaying materials are moving into and through decomposers.

Level 3 students will recognize that materials are moving during decay, but they are likely to explain mass loss as being caused by matter-energy conversions, leaving carbon dioxide, in particular, out of their accounts.

Application: Matter Change question

2. Developing and using models

6. Constructing explanations

7. Engaging in argument from evidence

8. Obtaining, evaluating, and communicating information

Identify the most abundant organic materials in decaying matter, including proteins and carbohydrates, and use food labels to find out how concentrated they are in different foods and animal tissues.

Explain the chemical changes that occur when a fungus digests food and creates new biomass.

Explain the chemical changes that occur during cellular respiration, representing the changes with molecular models and chemical equations.

Level 2 students will explain what happens as a natural process (the decaying material breaks down or is recycled) rather than as a chemical change in which atoms and mass are conserved.  They may recognize that decomposers are involved, but they will not consider decaying materials to be food sources for the decomposers.

Level 3 students will recognize that a chemical change is taking place, but they will not be able to successfully trace all the materials through the decay process.  They may say that the decaying matter is converted to energy or that all the matter is recycled through the soil.

Application: Energy Change question

2. Developing and using models

6. Constructing explanations

7. Engaging in argument from evidence

8. Obtaining, evaluating, and communicating information

Identify forms of energy involved in decay: chemical energy, movement, and heat energy.

Explain energy transformations during decay processes.  In particular, chemical energy stored in C-C and C-H bonds of organic molecules is used to support life processes in decomposers and is ultimately converted to heat.

Level 2 students will recognize that living organisms have energy, but may associate that energy with vitality (dead organisms have no energy) rather than with organic materials.

Level 2 students will not be committed to conservation of energy—the idea that decay processes MUST produce heat.

Level 3 students are likely to identify dead things as energy sources for animals, but they may not consider the same materials to be energy sources for decomposers.