jarEcosystem in a Jar

Purpose: In this lab you will observe the interaction of a snail and a water plant in a closed environment. The use of an indicator will allow you to observe the presence of oxygen and carbon dioxide in the environment.

See Teacher Notes for tips



Experiment Set-Up

Each container will have water plus 4 drops of BTB,. Use the chart to set up your 8 containers. Label each container with the number and letter (example 2B) -

Label Set 1 - placed under strong light Set 2 - placed in the dark
A nothing (control) - nothing (control) -\
B snail snail
C elodea stem with leaves elodea stem with leaves
D snail + elodea snail + elodea -\


Create a data table to record color changes in each of the containers. You will take data each day for three days. Also include a section of your data to analyze the health of the organisms.


1. Describe what happened in the experiment and propose an explanation for your observations.

2. Explain why some of the jars changed colors while others did not.

3. Describe how plants and animals are dependent on each other.

4. Make a prediction about what would happen in each the jars if they were left closed for a week.