Student Experience 5: How should we revise our pond model?

Purposes

For students to form and express connections among ideas from previous experiences about producers and their interactions with abiotic factors.
To assess the development of students’ understanding of how the fertilizer overload affects pond producers.

Description

Revisit the driving question and cross-sectional pond models students made in Student Experience 2. Ask students to again draw what they think might be happening in the pond based on what they have learned about producers. After they have completed their models, have students make comparisons to their original models.

Questions to Ask Students

Describe your model. Why do you think the things you included are important?
How is this model different from your first one? What have you learned that affected your new model?
How does your model help to explain what happens when nutrients in fertilizer get into the pond water?
How do you think the cloudy water will affect the plants that live under the water?

Science Practices

Developing and Using Models In this experience, students make revisions to their model. The questions above are intended to help students reflect on how and why their models are changing. At this early stage in students’ model development, it can be a good time to have students reflect on both the content and structure of their model to guide their work throughout the pathway.

One approach is to introduce students to the GAME guide sheet. Explain the different parts of the GAME mnemonic (Generality, Audience, Mechanism, and Evidence) and tell students they will use the guide sheet throughout this pathway. Assign small groups or pairs and have them exchange models and ask questions about each other’s models using the GAME guide sheet. Recognize that students may struggle with the questions during their first few times using the guide sheet. The goal is that they will begin to keep the GAME considerations in mind as they create and revise their models, not that they become proficient in this first experience. Allow time following the peer session for students to independently revise or add to their model. Circulate while students are working in small groups, or collect models afterwards to examine students’ models based on the teacher rubric. The rubric provides guidance for what you may want to ask students or do next in instruction to deepen their understanding.

Constructing Explanations Students’ revisions are driven by their new understandings and developing explanations of what is happening at Sunrise Farm Pond. Their models should reflect their thinking about the predicted causes, and these new predictions should be supported using evidence from the pond water and plant growth investigations.

Crosscutting Concepts

Cause and Effect Students’ thinking about the possible causes may have changed since their initial model. Encourage students to revise their model based on what they now predict are the causes and to be explicit about the relationship between the cause and effect.

Student Thinking

Seeing that fertilizer can promote algae growth, some students may now predict that algae growth is bad for fish and may think algae growth directly causes fish death. Some students may hold onto the idea that the fertilizer directly harms the fish.

Implementation Tips

Don’t do this activity before students see algae growth in Student Experience 3.
Depending on the models student produced in Student Experience 2, starting over with a fresh template, rather than revising the original, may be most practical.
As students revise their models, encourage them to represent the relative abundance of organisms by how many they include in their models. For example, five fish might represent a large population and two fish a small population. This relatively straightforward change can provide students a start for their revisions.
The last question above (How do you think the cloudy water will affect the plants that live under the water?) is intended to guide students to consider the fate of the underwater plants now that they get limited sunlight. You may need to guide a discussion to encourage students to connect the cloudy water to a lack of sunlight for these plants and their decreased ability to supply oxygen to the pond.
As noted above in Student Thinking, students may now think algae directly caused the fish death. Students may have heard that some algae do produce toxins that kill fish. However, most do not. In any case, let students know that there is more to the story at Sunrise Farm Pond and they will have further opportunities to modify their models.
A second sample pond model, which corresponds to this stage of the pathway, is available for your reference. Again, student models may not include all of the elements in the sample. Continue to use the rubric for student models to see how students’ thinking has progressed.