Question

Two students are planning an experiment that will test how planaria (aquatic flatworms) respond to different environments. They will conduct two investigations—one that tests the worms’ responses to different water temperatures and one that tests the worms’ responses to different levels of acidity. Student 1 wants to buy two groups of flatworms and use a different group for each investigation. Student 2 thinks the same group of worms should be used for both investigations. Do you think either student’s method would give more accurate results? Why or why not? Explain your response.

Answer 1

Answer:

The Student 1's method would bring more accurate results.

Explanation:

Student 1 wishes to use 3 healthy worm groups. The first group goes to environments with different water temperatures and the second group goes to an environment with different levels of acidity. As both groups had the same level of health it is possible to compare well the difference of influence of each environment on these worms. In addition, the third group was not placed in any different environment, so it remains healthy, so when compared to groups 1 and 2, it will be possible to know the different influences that the environment provided to healthy worms.

On the other hand, Student 2's method would use a single group for all environments and this would not show reliable results because the worm would accumulate effects from all the environments in which it entered.

Answer 2

Student 1’s methods would be more accurate, because the student would control more factors. Only one variable at a time (either temperature or acidity) would be tested on each group of worms. On the other hand, Student 2 is testing both factors on all the worms, which could make the results unclear.