Student Experience 6: More of the story

Description

Provide students with the story from Part One of the pathway, and continue with more of the story that corresponds to Part Two:
[stextbox id = “info”] Farmers at Sunrise Farm are planting crops for the season. They spread fertilizer on the field. The fertilizer contains chemical nutrients that help plants grow. Much of the fertilizer is used by the plants or absorbed by the soil, but not all. When it rains, some of the fertilizer goes into the stream by the field and flows into the pond.

Sunrise Farm Pond, like all ponds, has some algae growth. The algae grow slowly and have a very short lifespan. When the fertilizer runs into the pond, the chemical nutrients that help the crops grow also help the algae grow and reproduce much faster than they had previously.

The algae grow thick at the top of the water, which makes the water cloudy and blocks the sunlight from getting to the bottom of the pond where many producers live. As a result, it is difficult for the producers to grow and they eventually die. Normally, in the process of making their food, producers make much of the oxygen the pond needs. As they die, the amount of oxygen in the pond from these producers decreases.

Because algae have a very short lifespan, they die quickly, leaving a large amount of dead algae in the pond. The dead algae are consumed by bacteria, which are decomposers. Like all decomposers, the bacteria use oxygen in their process of consuming/decomposing the dead algae. There are a lot of dead algae, so the bacteria use a lot of the remaining oxygen in the pond.

When one of the farmers checks on the pond a few months after planting the crops, she finds that several of the fish have died.

Why are the fish dying at Sunrise Farm Pond?

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After sharing the story, use the Questions to Ask Students in a class discussion to encourage students to consider how their models relate to events in the story.

Questions to Ask Students

How does the story compare with your thinking about why the fish are dying in Sunrise Farm Pond?
How does your model represent what is described in the story?

Student Thinking

Some students may now believe that the decomposers are the sole reason for fish death.

Implementation Tip

Part Three will help students develop a complete understanding of the events at Sunrise Farm Pond.

Science Practices

Developing and Using Models After making revisions to their model in the previous student experience, students hear more of the story (an extension of what was shared at the conclusion of Part 1) and have an opportunity to reflect on how their model represents what is known now about the mystery at Sunrise Farm Pond.

Engaging in Argument from Evidence Like in Part 1, consider having students work again in pairs (though perhaps with a different partner) to explain how their models demonstrate what they think is happening at Sunrise Farm Pond. Revisit the GAME guide sheet to help facilitate these conversations. Providing an opportunity for students to examine and pose questions about a peer’s model will help students consider further revisions to make (e.g., adding clarification or evidence to support their ideas). Encourage students to use evidence to support their models when explaining them to a peer.

Asking Questions As done at the conclusion of Part 1, have students revisit the class-generated list of questions to see which, if any, they are now able to answer given their understanding of decomposers and their role. It is also important to again provide an opportunity for students to add questions that have emerged based on what they now understand about the mystery and what they think will be important to investigate. Many of the remaining or newly added questions are likely to be addressed in Part 3, which focuses on trophic relationships; however, students’ questions may also suggest what content may need to be revisited from Part 1 or 2.

Crosscutting Concepts

Cause and Effect Students can compare their thinking with what they have heard in the story to see the extent to which the causal relationships described in the story are reflected in their representation.

Stability and Change Attending to decomposers’ role in the pond, students are able to see how this rapid change (i.e., an increase in bacteria consuming dead algae) impacts the stability of the ecosystem via its impacts on the oxygen levels in the pond.

Systems and Systems Models Hearing more of the story about the system under investigation (Sunrise Farm Pond) enables students to reflect on how their model represents this system.