Dissolved oxygen is oxygen that is trapped in a fluid, such as water. Since many living organisms requiresoxygen to survive, it is a necessary component of water systems such as streams, lakes and rivers in order tosupport aquatic life. The dissolved oxygen is measured in units of parts per million (ppm). Examine the data inTable 4 showing the amount of dissolved oxygen present and the number of fish observed in the body of waterthe sample was taken from; finally, answer the questions below.
Table 4: Water Quality vs. Fish Population
Dissolved Oxygen(PPM) 0 2 4 6 8 10 12 14 16 18
Number of Fish Observation 0 1 3 10 12 13 15 10 12 13
1. What patterns do you observe based on the information in Table 4?
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.
3. What would your experimental approach be to test this hypothesis?
4. What would be the independent and dependent variables?
5. What would be your control?
6. What type of graph would be appropriate for this data set? Why?
7. Graph the data from Table 4: Water Quality vs. Fish Population (found at the beginning of this exercise).
8. Interpret the data from the graph made in Question 7.
Exercise 2: Experimental Variables
Determine the variables tested in the each of the following experiments. If applicable, determine and identify any positive or negative controls.
1. A study is being done to test the affects of habitat space on the size of fish populations. Different sized aquariums are set up with six goldfish in each one. Over a period of six months, the fish are fed the same type and amount of food. The aquariums are equally maintained and cleaned throughout the experiment. The temperature of the water is kept constant. At the end of the experiment the number of surviving fish as surveyed.
A. Independent Variable:
B. Dependent Variable:
C. Controlled Variables/Constants:
D. Experimental Controls/Control Groups:
2. To determine if the type of agar affects bacterial growth, a scientist cultures E. coli on four different types of agar. Five petri dishes are set up to collect results:
• One with nutrient agar and E. coli
• One with mannitol-salt agar and E. coli
• One with MacConkey agar and E. coli
• One with LB agar and E. coli
• One with nutrient agar but NO E. coli
All of the petri dishes received the same volume of agar, and were the same shape and size. During the experiment, the temperature at which the petri dishes were stored, and at the air quality remained the same. After one week the amount of bacterial growth was measured.
A. Independent Variable:
B. Dependent Variable:
C. Controlled Variables/Constants:
D. Experimental Controls/Control Groups:
Exercise 3: Testable Observations
Determine which of the following observations are testable. For those that are testable:
• Determine if the observation is qualitative or quantitative
• Write a hypothesis and null hypothesis
• What would be your experimental approach?
• What are the dependent and independent variables?
• What are your controls - both positive and negative?
• How will you collect your data?
• How will you present your data (charts, graphs, types)?
• How will you analyze your data?
Observations
1. A plant grows three inches faster per day when placed on a window sill than it does when placed on a on a coffee table in the middle of the living room.
2. The teller at the bank with brown hair and brown eyes is taller than the other tellers.
3. When Sally eats healthy foods and exercises regularly, her blood pressure is 10 points lower than when she does not exercise and eats fatty foods.
4. The Italian restaurant across the street closes at 9 pm but the one two blocks away closes at 10 pm.
5. For the past two days, the clouds have come out at 3 pm and it has started raining at 3:15 pm.
6. George did not sleep at all the night following the start of daylight savings.