At a city aquarium, a new tropical tank was installed to house a variety of fish, snails, and aquatic plants. The tank mimicked natural conditions: it had a light cycle, steady temperature, and regular feeding schedules. For the first week, the animals thrived. But within ten days, aquarium staff noticed the fish were gasping at the surface and several snails were unresponsive at the bottom. Water testing revealed dangerously low oxygen levels.

The tank had more than enough aquatic plants, which the staff assumed would maintain oxygen levels through photosynthesis. The lights were on for 12 hours per day, and no new chemicals had been added. Staff cleaned the filters and tested for common issues like pH or ammonia spikes, but results came back normal. Something else was causing the oxygen to drop.

After consulting with a marine biologist, staff began investigating cell processes. Samples were taken from water, plant tissues, and even slime on the rocks. Under a microscope, they found an unusual overgrowth of algae and bacteria. These organisms were not only multiplying rapidly, but they were also consuming oxygen faster than the plants could replace it. The expert explained that all living organisms, including plants, use oxygen during cellular respiration to break down sugars and produce energy.

The team realized they had overlooked one important detail: at night, when the tank lights were off, photosynthesis stopped, but cellular respiration continued. The algae bloom and decomposing waste from uneaten food increased the demand for oxygen overnight. The result was a dangerously low oxygen level by morning; too little for some of the animals to survive.

Directions

1) Homeostasis – How the body normally operates. For example, our body is usually 98.6 degrees F. If we have a fever, our body is out of homeostasis. 

2) Dynamic equilibrium – the body working to keep the body in homeostasis. 

3) Negative Feedback Mechanism – When the body responds to unnormal conditions so it can go back to homeostasis. 

Directions: Create a comic strip that represents a specific negative feedback loop. Use one of the negative feedback loops below or come up with your own. Research the negative feedback loop in order to make the comic. 

The comic must:

1) Be creative and colorful. 

2) Explain how the body is out of homeostasis (normal conditions). 

3) Explain how the body is trying to bring it back to normal conditions using negative feedback.