A researcher investigated the effect of different concentrations of glucose on the fermentation rate of yeast (*Saccharomyces cerevisiae*). Five test tubes were prepared, each containing of a yeast suspension and a specific concentration of glucose dissolved in distilled water. The tubes were maintained at for minutes. The volume of carbon dioxide () gas produced in each tube was measured to determine the rate of fermentation. The experimental setups are shown in the table below:
| Tube | Yeast Suspension () | Glucose Concentration () | Distilled Water () | Temperature () |
|---|---|---|---|---|
| 1 | 10 | 0 | 10 | 30 |
| 2 | 10 | 2 | 10 | 30 |
| 3 | 10 | 5 | 10 | 30 |
| 4 | 10 | 10 | 10 | 30 |
| 5 | 10 | 20 | 10 | 30 |
Which of the following tubes served as the control group to establish the baseline level of gas production in the absence of glucose?
- Tube 1, because it contains glucose, allowing the researcher to measure gas production in the absence of the independent variable.Answer
- BTube 3, because it contains a moderate glucose concentration of to represent typical environmental conditions.
- CTube 5, because it contains the highest glucose concentration of to show the maximum possible fermentation rate.
- DNone of the tubes, because a true control group would require a tube with glucose and water but no yeast suspension.
Answer
Tube 1, because it contains glucose, allowing the researcher to measure gas production in the absence of the independent variable.
The correct answer identifies the tube containing glucose. In an experiment, the control group is the baseline condition where the independent variable (in this case, glucose concentration) is absent, allowing researchers to isolate the effects of the independent variable.
Step-by-Step Solution
Key Concept
Determining Control Groups and Baseline Conditions
Estimated Time:1m 0s