Biology 101

Exercise 1:

Dissolved oxygen is oxygen that is trapped in a fluid, such as water. Since virtually every living organism requires oxygen to survive, it is a necessary component of water systems such as streams, lakes and rivers in order to support aquatic life. The dissolved oxygen is measure in units of ppm—or parts per million. Examine the data in Table 2 showing the amount of dissolved oxygen present and the number of fish observed in the body of water the sample was taken from; finally, answer the questions below.

Table 2: Water quality vs. fish population

Dissolved Oxygen (ppm) | 0 | 2 | 4 | 6 | 8 | 10 | 12 | 14 | 16 | 18 |

Number of Fish Observed | 0 | 1 | 3 | 10 | 12 | 13 | 15 | 10 | 12 | 13 |

1. Based on the information in Table 2, what patterns do you observe?

The number of fish observed increases as the units of ppm of dissolved oxygen in the water increases.

2. Develop a hypothesis relating to the amount of dissolved oxygen measured in the water sample and the number of fish observed in the body of water.

If the amount of dissolved oxygen in the water is increased, there will be more fish observed because oxygen is necessary for fish to live.

3. What would your experimental approach be to test this hypothesis?

Make 10 aquariums with different units (ppm) of dissolved oxygen (0ppm, 2ppm, …, 18 ppm) with the water from the same river and conditions the exact same as the river. Put all the aquarium in one room. Place 100 minnows from the same river in each tank. Take daily count on the number of fish in each aquarium. Proceed for 10 days, and remove dead fish from each aquarium.

4. What are the independent and dependent variables?

Independent Variable: Amount of dissolved oxygen

Dependent Variable: Number of fish observed

5. What would be your control?

Control variables: same temperature, body of water, amount of light, amount of fish food

6. What type of graph would be appropriate for this data set?...