Draw matter cycles and energy flow in a pond

Why do matter and energy need different arrows?

Submit: An evidence record, explanation and revision.

Related lesson: Ecosystems: Interactions

This is a teacher-led extension beyond the short lesson. The task supplies a performance opportunity; completion alone does not certify mastery, full NGSS coverage or state alignment.

Build the idea

Atoms can cycle among living things, water, air and soil. Energy enters many ecosystems as sunlight, moves through feeding and other processes, and ultimately leaves as thermal energy. Decomposers recycle matter; they do not send used energy back to the Sun.

Evidence and model inputs

Model components: sunlight, algae, grazing insects, fish, decomposers, dissolved carbon dioxide, water and sediment nutrients. The pond boundary includes water, organisms and sediment but excludes the Sun and distant atmosphere. The pond exchanges both matter and energy with its surroundings.

Keep actual observations, published findings and invented model cases labeled separately. If a source or required equipment is unavailable, pause that part with a teacher; do not invent results.

Materials and preparation

Paper, graph paper or spreadsheet, and the linked readings.

Grade-level scope

Conceptual models only; do not require chemical reaction equations.

Do the work

1. Place all components inside or outside the stated boundary.
2. Draw one complete carbon route from carbon dioxide through producers and consumers to decomposers and back to carbon dioxide.
3. Use a different line style for energy entering, moving through organisms and leaving as thermal energy.
4. Add matter exchange across the boundary and a key explaining each arrow.
5. Use the model to predict what happens to matter in a dead fish and revise any energy-recycling loop.

Learner worksheet

Write on paper or type here and print. Entries stay in this page’s memory and are lost when you leave or reload; they are not saved or submitted.

Check your reasoning

1. Do decomposers create new atoms?
2. What is the main energy input here?
3. Does energy cycle just like carbon?
4. Why specify the boundary?

Teacher review guide

Review the actual deliverable and discuss the reasoning. For each criterion, use 0 when evidence is absent or fundamentally incorrect, 1 when partly supported with a material error or omission, and 2 when accurate, supported and complete for the stated task. Maximum 8 points is a task score, not a proficiency certification. Give feedback and allow revision.

1. Defines a consistent system boundary.
2. Completes matter paths through living and nonliving components.
3. Separates energy flow from matter cycling.
4. Uses the model to explain a change and revise an error.

Sources and standard reference

• Official NGSS MS-LS2-3 performance expectation — inspect the practice, core idea, crosscutting concept and assessment boundary.

Instructional text and hypothetical cases are original. Linked source readings supply published evidence where specified. Teachers should judge fit with their course and state requirements.