Unit 9 Lab Report #1: A Pill Bug's Life

Tuck & Roll from A Bug's Life

Abstract

  For this lab, we are trying to find out what environment the terrestrial isopods (pill bugs) prefer to live by observing their behaviors. We collected 10 pill bugs and put them in a choice chamber, where two circular spaces of the same size are joined together. During the lab, the two sides of the chamber will be different from each other in only one aspect, while other conditions of two sides remain constant. By counting the number of pill bugs on the two sides and analyzing the data, we can find out which environment is more favorable to pill bugs.

Introduction

  To understand the purpose of this lab, one must first understand the definition of animal behaviors. The behavior is an animal's response to sensory input, and a behavior requires communication between animals through symbolic or chemical signals. In many cases, there are usually two types of explanations and questions for the behaviors. A proximate explanation or question relates to how the behavior occurs, and a ultimate explanation or question relates to why the behaviors occurs. Take an example of bird song, a proximate question for that behavior would be "How does the bird sing?", and an ultimate question would be "What is the purpose of bird song in nature?" 
  There are two categories for animal behaviors. The first category is innate behaviors, and it's categorized into reflexes and instincts. The reflex behaviors are the body's automatic responses to a stimulus, and they follow a neural pathway called the simple reflex arc. The arc often involves a sensory neuron, an association neuron and a motor neuron. The process of arc starts when the sensory neuron detects a stimulus, and the association neuron synapses with other neuron in order to send information to other parts of the body. Finally, the motor neuron responds to the stimulus in an effector cell, and the behavior occurs. The instinctive behavior is also the body's response to a given stimulus, but it's different from reflex because the behavior is not automatic, since the sensory neuron sends the impulse directly to the brain, and the brain have to respond to stimulus with account of the specific situation. 

Taxis movement - birds migrating to the south

  Orientation behaviors, a category for instinctive behaviors, are series of coordinated movements that are triggered by external stimuli. These behaviors include kinesis and taxis movements. The kinesis movement is an indirect motion in response to stimulus, and the pace of the motion is directly proportional to the intensity of the stimulus. An example of kinesis behaviors would be cockroaches scatter in random directions when there is a bright light shining upon them. The taxis movement, in contrast, is a specifically directed motion toward or away from the stimulus. An example of taxis movements would be the birds migrating to the south. The proximate cause of the migration would be the bird's ability to find directions with polarity in the Earth's magnetic field, and the ultimate cause of it could be the search for abundant food resources. 

Fixed action pattern - greylag goose rolling nearby eggs

  Some innate behaviors (especially instincts) followed fixed action patterns, which are stereotypical behaviors triggered by a sign stimulus in the surrounding environment, and completed once they begin. An example of fixed action patterns would be greylag goose, which continues to roll nearby eggs into the nest, even after the eggs are taken away. 

Imprinting behaviors - young geese mimicking their mother's actions

  The second category is learned behaviors, which include imprinting, classical conditioning, operant conditioning, habituation and insights. The imprinting behavior occurs when young animals go through a critical period when they follow the actions of parent animals. The example for imprinting behaviors would be young geese, which they follow the actions of their parents. A proximate cause for their imprinting behaviors may be that during their early development stage, the mothers of young geese choose to move away from the young geese and call them to begin the learning routine. The ultimate cause of those imprinting behaviors may be that young geese mimic the actions of their mothers to learn necessary skills, and survive in their habitat. 

Ivan Pavlov's experiment of classical conditioning

An alternative interpretation of the Pavlov experiment... by THE DOG

  The classical and operant conditioning are very similar learning behaviors for animals. Classical conditioning, also known as associative conditioning, is a behavior that the animal learns to link two unrelated stimuli together. A "classic" experiment on classical conditioning (haha) was done by Ivan Pavlov, a Russian Nobel-prize-winning scientist. In the experiment, the dog had no reaction to the tuning fork and drooled when the food is provided before the conditioning. During the conditioning, Pavlov provided food to the dog after he rang the tuning fork. After the conditioning is over, the dog would drool when it hears the tuning fork. The experiment successfully proved that animals can learn through conditioning or reoccurring events.   

The Skinner experiment on operant conditioning

  The operant conditioning is quite similar to classical conditioning. However, the behavior is also known as the trial-and-error conditioning because the animal receive rewards or punishment to learn the behaviors. An experiment was done by psychologist B. F. Skinner. In the experiment, Skinner taught the rat to press the lever by associating the action with the food reward. In contrast, he also taught another rat not to press the lever by electrifying the lever, and using it as a punishment. 
  Therefore, by observing the actions of the pill bugs moving to two sides of the chamber, we can determine whether their movements are innate or learned behaviors, thus discover which side of environment is more suitable for pill bugs. Finally, our question for the lab is "Do the pill bugs prefer the lighted environment or the dark environment?"

Hypothesis

  To answer the question, the independent variable of our lab should be the difference of light exposure on two sides of the chamber, and the dependent variable would be the number of pill bugs on each side. The constants in our lab would be the same size of two circles of the chamber, the total number of pill bugs, temperature and pH level. 
  In general, we hypothesized that if the pill bugs are put in two environments with different lighting, then the pill bugs will choose the dark environment, because dark environment has a higher humidity level than the lighted environment, which is necessary for pill bugs' survival in their habitat. 

Materials

1. two choice chambers
2. two pieces of filter paper
3. 10 pill bugs
4. a lamp
5. a paint brush
6. data sheet
7. timer

Procedure

the 10 pill bugs we collected in the 1st choice chamber

• At first, we put the 10 pill bugs we collected in one choice chamber. 
• Later, we placed two pieces of filter paper on both sides of the other choice chamber.
• Then, we moved the bugs to the choice chamber with filter papers with the paint brush.
• We turned on the lamp and put the left side of the chamber under the light.
• Later on, we covered the right side of the chamber with the first chamber we used, in order to block the light. 

This is what the setup looks like...

• Using the timer, we counted the number on each side of the choice chamber every 30 seconds. We stopped recording after 5 minutes of data.
• We turned off the lamp, moved the pill bugs into the stock chamber, and cleaned the choice chamber to finish the lab. 

Data
  

Click on the data to enlarge

Conclusion

  From our collected data, we can see that despite the trend of pill bugs moving toward the lighted side in the first and third minute, there were always more pill bugs on the dark side than those on lighted side, which proved our hypothesis correct. Thus, we concluded that the pill bugs are more comfortable living in dark environment than living in lighted environment. One mistake in our lab was that the difference between two sides of the chamber on the independent variable (lighting) is not apparent, since some pill bugs on the dark side of the chamber began crawling under the filter paper at 2 minutes after the lab started. 

Citation

    Magliore, Kim. The Princeton Review: Cracking the AP Biology Exam 2014. N.p.: Princeton Review, 2013. Print.

- Andy Liu '15