All living organisms, including invertebrates, can respond to the stimuli in their environment. In this assignment, you will plan an investigation to study the response mechanism of an invertebrate (e.g. earthworm) to an external stimulus (e.g. light, sound, touch). In your investigation, you must reveal the usual response of the invertebrate to the stimulus, and then modify (change) it to study how the response might change.
An earthworm was used as an example of an invertebrate in the description of this activity because it is generally easy to obtain. However, you may choose to plan your procedure using another invertebrate and a different external stimulus.
Your task is to plan and conduct a simple experiment to test how an invertebrate responds to a change in stimulus using common household items found around you. As an inquiry-based activity, you need to design your own experiment, including the following:
- Determine an appropriate ‘Testable Question’.
- Propose a reasonable hypothesis based on your ‘Testable Question’.
- Develop a procedure based on your ‘Testable Question’.
In this experiment, you may want to investigate the response of an earthworm to a stimulus. You must first reveal the usual response of the earthworm to the stimulus before you change it to investigate its response.
As an example, you may be interested in how an earthworm will respond to the salinity of the soil. Before you change the salinity, you must first determine what the normal salinity is in the soil around you. This is your control that you can use to compare the response when you adjust (increase or decrease) the salinity in your planned investigation.
It is important to understand the baseline (or usual) response to the stimuli before you change it in your experiment.
Step 1: Planning Your Experiment
- Determine the testable question you wish to investigate. Ensure that your testable question can be answered using quantifiable data and not simply qualitative observations.
- Once you have decided on your testable question, propose a reasonable hypothesis for the experiment you plan to conduct. Your hypothesis should explain how the change in your independent variable will affect your dependent variable. As previously stated, the change in your dependent variable should be quantifiable.
- Develop the procedure for the experiment you intend to conduct to test your hypothesis. Your procedure should be specific and detailed, allowing another scientist to recreate your experiment using the exact steps you used in your investigation. Write the steps of the procedure in the past tense.