BIOL 3270 – Zoology
Fall 2021
Lab Assignment 2
Answer the following questions by typing your answers directly into the document below each question. This
assignment is due in the dropbox by Monday September 27 at 2:00PM. An assignment turned in at 2:01PM is
considered late and will incur a late penalty as outlined in the syllabus.
1. Do planaria response the same way when egg yolk and liver were added? Does the response occur more
quickly with one food source over the other? Provide evidence for your conclusion. (5 pts.)
Yes, planaria respond in the same way to egg yolk as they do to liver. They also do not appear to respond more quickly
to one stimuli over the other, as both stimuli trigger their chemoreceptors (located in their auricles) in the same way.
After these receptors have been stimulated, the planaria does not adjust their response depending on which food is
supplied, but instead reacts in an instinctive and stereotyped manner towards the food.
2. How did your planaria respond to light shined at its anterior end vs. from the side? Why does it respond
this way? (5 pts.)
When the light was shined on the anterior end of the planaria, they reacted by moving away into an area with less light
(ie under the shaded part of the petri dish). This is because the eyespots, which are sensitive to light, are present. At the
anterior end of the planaria, and so they detected the light stimuli and reacted accordingly. Conversely, the planaria did
not react when the light was shined on its side. As they do not possess any light deteccting organs on the sides of their
body, they were unaware of the changes in light stimuli occurring, and so they had no reason to respond to the stimulus.
3. After shining and poking the planaria 100 times, what was the response when you shined the light but did
not poke the planaria? Does this demonstrate learning in your view? How many flahses of light are required for the
flatowrm to stop reacting to the uncoupled stimulus? (5 pts.)
The planaria had learnt that when the light was shone, it would be followed by a poke. It had then conditioned itself to
respond to the light by curling up in an attempt to protect itself from the expected stimuli that followed. This did
demonstrate learning to me, as it showed that the planaria was able to recognize that a light being shone meant
imminent poking, and so it learned to respond before the stimulus was actually applied. It took the planaria between 20-
30 solitary flashes before it learned to stop reacting to a stimulus that was no longer present.
Fall 2021
Lab Assignment 2
Answer the following questions by typing your answers directly into the document below each question. This
assignment is due in the dropbox by Monday September 27 at 2:00PM. An assignment turned in at 2:01PM is
considered late and will incur a late penalty as outlined in the syllabus.
1. Do planaria response the same way when egg yolk and liver were added? Does the response occur more
quickly with one food source over the other? Provide evidence for your conclusion. (5 pts.)
Yes, planaria respond in the same way to egg yolk as they do to liver. They also do not appear to respond more quickly
to one stimuli over the other, as both stimuli trigger their chemoreceptors (located in their auricles) in the same way.
After these receptors have been stimulated, the planaria does not adjust their response depending on which food is
supplied, but instead reacts in an instinctive and stereotyped manner towards the food.
2. How did your planaria respond to light shined at its anterior end vs. from the side? Why does it respond
this way? (5 pts.)
When the light was shined on the anterior end of the planaria, they reacted by moving away into an area with less light
(ie under the shaded part of the petri dish). This is because the eyespots, which are sensitive to light, are present. At the
anterior end of the planaria, and so they detected the light stimuli and reacted accordingly. Conversely, the planaria did
not react when the light was shined on its side. As they do not possess any light deteccting organs on the sides of their
body, they were unaware of the changes in light stimuli occurring, and so they had no reason to respond to the stimulus.
3. After shining and poking the planaria 100 times, what was the response when you shined the light but did
not poke the planaria? Does this demonstrate learning in your view? How many flahses of light are required for the
flatowrm to stop reacting to the uncoupled stimulus? (5 pts.)
The planaria had learnt that when the light was shone, it would be followed by a poke. It had then conditioned itself to
respond to the light by curling up in an attempt to protect itself from the expected stimuli that followed. This did
demonstrate learning to me, as it showed that the planaria was able to recognize that a light being shone meant
imminent poking, and so it learned to respond before the stimulus was actually applied. It took the planaria between 20-
30 solitary flashes before it learned to stop reacting to a stimulus that was no longer present.
