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.

Answer 1

Student 2 is right.

Constant variables

In research investigations, some variables should be kept constant across various experimental groups in order for the outcome of the investigation to be valid.

For example, in order to test how flatworms respond to different environments, one variable that should be kept constant is the flatworms. The flatworms to be used must be of the same species, sex, age, etc.

The investigator can then go ahead to divide the flatworms into two or more groups and then subject them to different environments. Other variables should also be kept constant in order to determine the effects that are only specific to the different environments only.

More on constant variables can be found here: brainly.com/question/474060

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