A group of students conducted a baseline experiment to measure the rate of transpiration in tomato plants under still-air conditions at a constant temperature of and relative humidity. They measured transpiration by recording the mass loss of a plant over time using a digital scale.
Suppose the students want to modify this experiment to investigate the specific, independent effect of wind speed on transpiration rate using a variable-speed fan and an anemometer (wind gauge). To ensure a valid follow-up experiment, in what order should the students perform the following procedural steps?
- 1Place the plant in a chamber with the temperature and relative humidity fixed at and to control these variables.
- 2Use the anemometer to calibrate the fan settings to establish three distinct, constant wind speeds.
- 3Position the plant on a digital scale in the path of the fan operating at one of the calibrated wind speeds.
- 4Record the plant's mass at regular intervals over to determine the transpiration rate for that wind speed.
Answer
The correct sequence starts with establishing control variables (temperature and relative humidity), followed by calibrating the wind speeds using the anemometer, placing the plant on the scale in the wind path, and finally recording the plant's mass loss over time.
The correct order begins with establishing the control variables (temperature and relative humidity) at their baseline levels to isolate the effect of wind speed. Next, the new independent variable must be calibrated by measuring the fan settings with the anemometer. Once calibrated, the plant is positioned on the scale in front of the fan. Finally, the dependent variable (mass loss over time) is measured to determine the transpiration rate.
Step-by-Step Solution
Key Concept
Designing follow-up experiments requires isolating the new independent variable by holding all other variables constant at baseline levels, calibrating the independent variable, setting up the test subject, and then measuring the dependent variable.