Student Experience 5: The whole story

Description

Provide students with the story from Parts One and Two of the pathway, and add the final part of the story that corresponds with Part Three:
[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.

The oxygen in the pond significantly decreases, so the things in the water that need oxygen to survive begin to die. As organism populations decrease, it causes a shortage in other populations’ food supply. Mayfly larvae begin to die first because they are unable to move to other, more oxygen-rich areas of the pond. With fewer mayfly larvae, the minnows and perch compete for the food. Because perch also consume minnows, the minnow population decreases, both because they have a limited food supply (mayfly larvae) and are being eaten by perch. When one of the farmers checks on the pond a few months after planting the crops, she finds that several of the perch have died, because the minnow population decreased and perch had limited food supply so they also died.

When pond organisms die, decomposer activity increases at all levels, which uses oxygen and continues to decrease oxygen in the pond.

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After sharing the complete 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

We’ve solved the mystery! Sharing the solution is an important next step. Imagine you’re the reporting detective—using your own words and/or pictures, explain why the fish are dying at Sunrise Farm Pond.
How does the story compare with your earlier models/thinking about why the fish are dying in Sunrise Farm Pond?
How does your model represent what is described in the story?
Would you add anything to your model to help support this story?
How do you feel about working together to figure out why the fish were dying in Sunrise Farm Pond? When did you realize how all the pieces fit together? Are there any other questions about what happened at Sunrise Farm Pond? How could we find out?

Science Practices

Developing and Using Models After making revisions to their model in the previous student experience, students hear the whole story and have an opportunity to reflect on how their model represents the causes behind the mystery at Sunrise Farm Pond. It may be helpful to ask students to consider how they can account for both visible and non-visible causes in their model.

Constructing Explanations As students take on the role of a reporting detective, they draw on their model and experiences throughout the pathway as evidence to explain why the fish are dying at Sunrise Farm Pond. It may be helpful to direct students to the prompts in the “Evidence” section of the GAME guide sheet as they construct explanations.

Asking Questions Even with a complete understanding of the events that transpired at Sunrise Farm Pond, students may have remaining or additional questions, such as, “What will happen now?” See potential extension activity suggestions below.

Crosscutting Concepts

Cause and Effect At this stage, it is important that students’ models reflect the directionality and extent of cause-and-effect relationships among abiotic and biotic factors at Sunrise Farm Pond. By understanding the nature of relationships, students are more likely to be able to apply these ideas to other contexts. For example, considering the relationships within a different ecosystem.

Stability and Change Initially, students may have thought that the fertilizer had a direct, toxic impact on the ecosystem resulting in the disturbance (dying fish). However, after the experiences in the pathway, students are able to see how the stability of Sunrise Farm Pond was gradually impacted by effects to multiple organisms in the ecosystem, and how it was ultimately decreased oxygen that led to the fish dying.

Systems and Systems Models After hearing the entire story, students compare their thinking with the story to see the extent to which their representation clearly depicts the solution to the mystery and the system under investigation (Sunrise Farm Pond).

Extensions

Students may wonder how Sunrise Farm Pond will recover from this disturbance. Options for extension allow for connections to Language Arts or Engineering:
- For example, we recommend reading the following article, which poses one potential remedy for a case of nutrient pollution.
  https://www.sciencenewsforstudents.org/article/fighting-big-farm-pollution-tiny-plant
- Alternatively, leverage students’ questions about how the pond will recover to engage students in an engineering design challenge. The challenge could focus on stabilizing the pond environment, or designing a system to prevent such disturbances in another local ecosystem.
Pose an alternate scenario to students. For example, have students consider how the story may have been different had the farmer added an organism, such as snails (which eat algae), to the pond when she noticed all of the algae. Provide students with a few pieces of information, including: (1) snails eat algae, (2) snails eat underwater plants, (3) snails eat dead organisms, and (4) perch eat the snails. Encouraging students to use this information and what they’ve learned throughout the pathway, engage students in a discussion about how things might have played out, or have students develop a model and use it to explain what might happen. If the latter, elements of the rubric used elsewhere in the pathway can be used for scoring students’ work. (Please note that although there are ways that students’ models and explanations can be inaccurate, there is no single “right” answer.)