Question

Open the Gizmo called "Plants and Snails" and hit "Launch

HYPOTHESIS
Before testing, PREDICT with the lights on how the oxygen and carbon dioxide levels might change in the tubes below.
State your hypothesis by adding a statement into the blank using the words Drop, Increase or Little Change. Be sure to hit enter after you type in your response. Pick your prediction for each test tube.
Test Tube A: If we add a snail to the test tube, then the O2 levels will
and CO2 levels will
.
Test Tube B: If we add an elodea plant to the test tube, then the O2 levels will
and CO2 levels will
.
Test Tube C: If we add an elodea and a snail to the test tube, then the O2 levels will
and CO2 levels will
.

Answer 1

Test Tube A: If we add a snail to the test tube, then the O2 levels will Drop and CO2 levels will Increase.
Reason: The snail respires (uses O2, releases CO2).

Test Tube B: If we add an elodea plant to the test tube, then the O2 levels will Increase and CO2 levels will Drop.
Reason: In light, the plant photosynthesizes (produces O2, consumes CO2).

Test Tube C: If we add an elodea and a snail to the test tube, then the O2 levels will Little Change and CO2 levels will Little Change.
Reason: The plant and snail can offset each other (plant makes O2 and uses CO2 while the snail uses O2 and makes CO2), so levels may stay about the same.