26 Eutrophication-S - POGIL assignment-Eutrophication ... - Free Printable

The image you've uploaded is a worksheet titled "Eutrophication", focusing on how aquatic ecosystems change over time, particularly through the process of eutrophication. It includes a diagram labeled Model 1 – Biological Oxygen Demand, showing a small lake ecosystem with fish, plants, decomposers, and sunlight.

Below are the answers to the questions in Question 1, along with an explanation for each:

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1. Consider the small lake in Model 1.

#### a. What organisms in the lake require oxygen to survive?
✔ Answer: *Fish* (and decomposers)

🔹 Explanation:
Fish need dissolved oxygen in the water to breathe through their gills. Decomposers (like bacteria and fungi) also require oxygen to break down dead organic matter. While not explicitly mentioned in your answer, decomposers are also aerobic organisms that consume oxygen. So, both fish and decomposers require oxygen.

> ✔ Correct answer: Fish and decomposers

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#### b. What organisms in the lake produce oxygen that dissolves in the water?
✔ Answer: *Plants*

🔹 Explanation:
Aquatic plants (such as algae and submerged vegetation) perform photosynthesis using sunlight, carbon dioxide, and water to produce glucose and oxygen as a byproduct. This oxygen dissolves into the water and becomes available for fish and other organisms. The sun's energy is shown in the diagram driving this process.

> ✔ Correct answer: Plants (specifically photosynthetic organisms like algae and aquatic plants)

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#### c. What characteristics of this lake make it “healthy”?
✔ Answer: *Has fish, plants, and decomposers*

🔹 Explanation:
A healthy lake ecosystem has:
- Producers (plants) – to generate oxygen and food via photosynthesis.
- Consumers (fish) – indicating sufficient oxygen and food sources.
- Decomposers – to recycle nutrients from dead organisms.
- A balance between oxygen production and consumption.
- Clear signs of biological activity without excessive algal growth or dead zones.

This balance suggests stable nutrient cycling, adequate dissolved oxygen, and biodiversity, all hallmarks of a healthy aquatic ecosystem.

> ✔ Your answer is correct and well-reasoned! You could enhance it slightly by mentioning balanced oxygen levels and presence of diverse life forms.

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🌱 Summary of Key Concepts:

- Oxygen demand: Organisms like fish and decomposers consume oxygen.
- Oxygen supply: Produced by photosynthesis in plants and algae.
- Healthy lake: Has balanced populations, sufficient oxygen, and functioning food web.
- This model sets up the idea that if too much nutrient input (e.g., from fertilizers) occurs, it can lead to eutrophication — excessive plant growth → algal blooms → death of plants → decomposition → oxygen depletion → fish kills.

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Let me know if you'd like help answering the next set of questions (likely about eutrophication stages or human impacts)!