Purposes
- To identify events that are impacting the organisms living in the pond.
- To identify organisms’ needs for survival.
Description
Prompt students to recount the events up to this point in the instructional sequence (e.g., algae overgrowth as a result of nutrient overload, algae blocking light from producers). After the class has generated a list of events, ask students to think back about the needs of consumers and producers. Facilitate a discussion about how these events are affecting organisms’ ability to meet their needs in the pond, highlighting differences between consumers (including decomposers) and producers. Record the suggestions for potential impacts.
Questions to Ask Students
- Think about the ways that you have changed/added to your diagram over time. What have we noticed happening in the pond?
- What have we added to our models? Why?
- In what ways did the increased growth of algae impact other producers’ needs?
- What do producers supply?
- What do decomposers use as they feed on the dead algae?
- How does the decomposers’ use of oxygen relate to the needs of the other organisms?
- What do consumers need to survive?
- How do producers’ needs differ from consumers’ needs?
- How are the consumers’ and producers’ needs being met in this environment?
Student Thinking
- Students may not recognize non-living factors as part of an ecosystem or believe that organisms are not affected by these abiotic factors. In the case of the pond, students may find it difficult to understand how the decreased levels of oxygen would affect the organisms.
- Additionally, students may view abiotic factors as unchanging. In this case, they may have difficulty understanding that the oxygen levels will change based on the level of decomposer activity.
- At the other extreme, students suggest that abiotic factors affect all organisms equally. In the case of the pond, students may think that the fertilizer is universally toxic to all organisms.
- Students may not recognize natural, biodegradable, or non-visible entities as pollutants. Therefore, students may find it difficult to see the nutrients entering the water as a “pollutant.”
Implementation Tips
- Keep the list of potential impacts as a starting point for the next student experience. Sample impacts generated by students may include:
- nutrients from fertilizer allow the algae to grow very quickly
- algae growth causes the water to become cloudy and blocks sunlight to producers
- decomposers use a lot of the oxygen in the pond as they consume the dead algae
- mayfly larvae do not have enough oxygen and begin to die
- without mayfly larvae to consume, the minnows begin to die
- without mayfly larvae or minnows to consume, the perch begin to die
Crosscutting Concepts
Cause and Effect In this experience, students are asked to consider the impacts of events at Sunrise Farm Pond. By defining these individual causal relationships, students are building the foundation for solving the mystery, which requires sequencing the impacts of multiple events.
- It may be helpful to depict how organisms in the class-created food web can be categorized as consumers and producers. This representation may help students to see how these organisms share common needs. (See example below.)
- Although students may mention several environmental conditions (e.g., temperature, shelter), or interactions among organisms (e.g., protection, defense strategies), it is most important to focus on the oxygen and the effects of depleted oxygen levels on the perch’s food sources to determine the cause of the dead fish (see example below).
