Date and Analysis (Biology)

Question

A team of students wants to study the effect of temperature on bacterial growth. They put the dishes in different places: an incubator (37°C), a lab room (21°C), a refrigerator (10°C) and a freezer (0°C). Bacterial growth is measured by estimating the percentage of each dish that is covered by bacteria at the end of a 3-day growth period.

1. What type of graph would be used to present these data? Explain why. 
2. Identify your independent and dependent variables
3. Identify your controls

Answer 1

Hi Gabriel,

It is important to focus on the research question which will lead you to answers for all three questions.

Question is : What is the effect of temperature on bacterial growth? Experiment to answer this question involves changing the temperature (manipulating this variable) and measuring growth of bacteria in 3 days (measuring/observe this variable).

I will answer question 2 first

2) Independent variable is the variable you deliberately manipulate because you are investigating the effect of this variable so here, temperature is the independent variable. The dependent variable is the variable you measure because you are monitoring the effect of independent variable on this variable. So here bacterial growth.

1) Now for question 1, you always put independent variable on the x axis and dependent variable on the y-axis. Both axes are numbers so it makes sense to make a line graph to show the effect of temperature on bacterial growth.

3) Controls are variables you want to keep the same in your experiment such that the experiment only looks at the effect of temperature and nothing else. So you would want to control variables such as type of bacteria, time left to grow, humidity, oxygen content etc. in all the groups even though they are in different temperatures.

If you are interested in learning more about these concepts with other examples, I would be happy to schedule a tutoring session with you.