Biology // Scientific Method
Name______________________________________ Pd _____
1. You are testing a new drug that supposedly stops sneezing in people allergic to grass. What is
the dependent variable?
A student noticed that when a dog is cut, the dog periodically licks his wounds. After a few days,
the wound begins to heal without ever showing signs of infection. The following steps outline the
student’s line of reasoning:
A. I wonder why the dog’s wounds don’t get infected.
2. You want to see if playing music makes plants grow taller. What is the independent variable in
this experiment?
3. An entomologist wants to determine if changes in temperature determine how often crickets
chirp. What is the dependent variable?
4. You want to measure the effect of different amounts of oxygen on the rate of yeast growth.
What is the dependent variable?
5. You think that a certain part of your brain is important in memory. To test this, you will
remove this part of the brain from rats and see if they remember how to get through a maze.
What is the independent variable in this experiment?
6. Orchids were studied to determine if the amount of humidity affected the flowering. What is
the independent variable in this experiment?
Questions 7– 10 refer to the following experiment: Suzy Q wants to know how different colors of
light affect the growth of plants. She believes that plants can survive best in white light. She buys
5 ferns of the same species, which are all the same age and height. She places one in white light,
one in blue light, one in green light, one in red light, and one in the closet. All the ferns are
served with Miracle-Grow and given 20 mL of water once a day for 2 weeks. After 2 weeks, suzy
observes the plants and collects measurement data.
B. If the dog’s saliva is present, then the growth of infection-causing bacteria will be
prevented.
C. I’ll obtain a bacterial culture and grow the same kind of bacteria in two identical
culture dishes. Once the bacteria start growing, I’ll add dog saliva to only ONE of the
dishes and leave the other alone. I’ll cover both dishes, and then observe what
happens for one week.
D. Even after adding the dog saliva to one of the dishes, the bacteria continued to
grow in BOTH dishes over the course of the week. However, the growth of bacteria in
the dish treated with dog saliva was slower than the untreated dish.
E. I think I’ll try something else; I’ll start with two identical culture dishes, and use the
same type of bacteria in each dish, but this time I’ll treat one dish with dog saliva
BEFORE I add the bacteria. I’ll observe what happens for one week.
11. What part of the scientific method is illustrated in step A?
12. What part of the scientific method is illustrated in step B?
13. What part of the scientific method is illustrated in step C?
14. What is the independent variable in the student’s experiment?
7. What measurements could Suzy make to determine how different colors of light affect the
growth of plants?
15. What is the dependent variable in the student’s experiment?
8. What is the independent variable in this experiment?
16. What is the control in this experimental design?
9. What is the dependent variable?
17. Why were both dishes covered?
10. What are the control variables?