Question

In the same science fair, Tina asks the question “Does caffeine increase the heart rate of an earthworm?” In Test 1, she measures the heart rate by looking at the earthworm under a microscope, the earthworm has a heart rate of 50 bpm (beats per minute). In Test 2, she places a few drops of caffeine on the earthworm’s skin and measures the rate again. In this test, the heart rate is 68 bpm.

List three controlled variables in this experiment.

Answer 1

Controlled variables are:

- amount of caffeine she adds

- earth worm (in natural state)

- how much caffeine is actually absorbed by the worm

Step-by-step explanation:

Answer 2

Independent variable- effect of caffeine

Dependent variable- heart rate

Hypothesis- If a stimulant such as caffeine is administered to earthworm, then its heart rate increases. The experiment is based on the research question; "Does caffeine increase the heart rate of an earthworm?" We can see from this research question that the independent variable is the effect of caffeine and the response it produces is a change in the heart rate (the dependent variable)

This now leads us to a hypothesis that states thus; 'If a stimulant such as caffeine is administered to earthworm, then its heart rate increases.'

Controlled variables are:

- amount of caffeine she adds

- earth worm (in natural state)

- how much caffeine is actually absorbed by the worm