A bottle ecosystem is a small sealed terrarium that lets you observe how living and nonliving parts of an ecosystem interact. Inside the bottle, plants, soil, water, air, and decomposers form a miniature system that can change over days and weeks. This project matters because it makes invisible cycles, such as water movement and nutrient recycling, easier to see.
By tracking changes for 4 weeks, students can connect observations to real ecosystem processes.
Key Facts
- Photosynthesis: carbon dioxide + water + light energy -> glucose + oxygen.
- Cellular respiration: glucose + oxygen -> carbon dioxide + water + energy.
- In a sealed bottle, water cycles by evaporation, condensation, and dripping back into the soil.
- Plants need light, water, carbon dioxide, nutrients, and space to grow.
- A fair test changes only one independent variable at a time, such as water amount, light level, or plant species.
- Percent change = ((final value - initial value) / initial value) x 100%.
Vocabulary
- Terrarium
- A terrarium is a clear container that holds plants, soil, and water to model a small ecosystem.
- Ecosystem
- An ecosystem is a community of living organisms interacting with each other and with nonliving parts of their environment.
- Condensation
- Condensation is the change of water vapor into liquid droplets when it cools on a surface.
- Decomposer
- A decomposer is an organism, such as a fungus or bacterium, that breaks down dead material and returns nutrients to the soil.
- Variable
- A variable is a factor in an experiment that can be changed, measured, or kept the same.
Common Mistakes to Avoid
- Adding too much water, which can flood the soil and reduce the oxygen available to roots and decomposers.
- Changing several variables at once, which makes it impossible to know whether water amount, light, plant species, or another factor caused the result.
- Placing the bottle in harsh direct sunlight, which can overheat the sealed system and cook the plants instead of helping them grow.
- Opening the bottle repeatedly, which breaks the sealed-system model and changes the water, air, and microorganism balance inside.
Practice Questions
- 1 A student adds 60 mL of water to one bottle and 90 mL to another identical bottle. How many more milliliters of water does the second bottle receive, and what percent more water is that compared with the first bottle?
- 2 A plant in a bottle terrarium is 8 cm tall on day 1 and 11 cm tall on day 28. What is the plant's growth in centimeters, and what is the percent change in height?
- 3 Two sealed bottle ecosystems are built the same way, but one is placed near a bright window and the other is placed in dim light. Explain how light level could affect plant growth, condensation, and oxygen production over 4 weeks.