1. Explore: To investigate the question, measure the oxygen concentration and go fishing in several ponds. (To fish, drag the Fishing pole into the pond, click Play, and wait several hours.) Observe the oxygen concentration and the numbers and types of fish you catch.
2. Form hypothesis: How does oxygen concentration affect the fish that live in a pond?
3. Predict: If you fish in four ponds, will more fish be caught in the two ponds with the lowest oxygen concentrations, or the two ponds with the highest oxygen concentrations? Explain.
4. Test: Investigate four ponds. For each pond, measure the dissolved oxygen concentration at 6:00 AM. Fish for six hours and record how many catfish and trout you catch in each pond. (Hint: To find a pond with relatively high levels of dissolved oxygen, click No farms.)

Oxygen (6:00 AM) Number of catfish Number of trout
Pond 1
Pond 2
Pond 3
Pond 4