Teach lesson
Planarians in motion: water and sugar
Students use the Planarians remote lab to predict, count line crossings, and compare movement in pond water and sugar water.
First time activating Teach? You can run one class session at no cost. Students join with a class code.
New to LabsLand? Create your teacher account
Learning Outcomes
Apply one simple, consistent rule to count complete line crossings in the lab view.
Record two line-crossing counts, one in pond water and one in sugar water, using the same rule and the same amount of time.
Compare the two counts and choose a conclusion that does not go beyond what was observed.
Student activity preview
Activity Content
Preview only. In a class session, students can fill in responses and submit their work to the teacher.
Look before you measure
5 min
Planarians are small flatworms that live in water. They have soft bodies, broad heads, and two small dark spots that sense light, called eyespots. Although their nervous system is much simpler than ours, they can find their way around and move through their environment.
In this activity, you will observe recordings of real planarians. You will compare their movement in pond water and sugar water. The question is: will they make about the same number of line crossings in both conditions? You will count the crossings and decide what you can say from just two observations.
Observe with respect
The recordings show living organisms. Describe only the movement you can observe. A crossing count cannot tell us what a planarian feels or predict effects in people.
Challenge 1 · Before you observe: what do you think will happen? Each dot represents one line crossing.
Challenge 2 · The counting rule: the picture is enlarged. In which scene would you add 1?
The rule will always be the same: add 1 only when the head passes completely from one side of a line to the other. Touching the line and turning back does not count.
Observe and count
16 min
Before you begin, look at the grid. Always use the same rule: add 1 when the planarian's head passes completely from one side of any grid line to the other. Touching a line and turning back does not count. Use the head as your reference point in both conditions.
Open the Planarians lab
Open the lab from this block. Under Solution, choose Pond Water.
Select
Start experiment. The recording and timer will start, and the counter will be at 0.Each time you see a complete crossing, select
Count uponce.Stop counting when the first timer value reaches 00:01:00. The display shows time as
00:00:00 / 00:05:00. If you pressedCount uponce too many, selectCount downonce to subtract 1.Resetclears the whole count: do not use it to correct just one mistake.Write down the number. Select
Restart experiment, choose Sugar, and then selectStart experimentagain.Apply the same rule until 00:01:00. Return to Teach and complete your table with both counts. You do not need to calculate crossings per minute.
My two observations
Record the pond-water count in the ‘Pond’ row and the sugar-water count in the ‘Sugar’ row. The 60-second times are already filled in. For each row, enter only the counter value when the elapsed time reaches 00:01:00.
| Condition | Time s | Total |
|---|---|---|
Compare your results
4 min
Look at the two numbers in your table. Your conclusion should describe these two observations, even if another person or group gets different numbers.
In your table, the number of crossings in sugar water was…
Look at your two numbers. Which sentence best matches what you observed?
Before you finish, think back to your prediction. Being right was not the important part: what matters is comparing it with what you observed.
Turn this preview into a live class session
Activate LabsLand Teach to use this lesson with your students. The first time you activate Teach, you can run one class session at no cost.
New to LabsLand? Create your teacher account