Laboratory Activity

Observing Behaviors: Pillbug Behavior

Unit I: Cell Structure and Function

Time Allotment: 45 -50 minutes

PASS Objectives:

Content Standarad (CS): 6.2 Responses to external stimuli can result from interactions with the organism’s own species and others, as well as environmental changes; these responses either can be innate or learned. Broad patterns of behavior exhibited by animals have changed over time to ensure reproductive success.

Process Standard 1-6

EOI Item Specifications

Emphasis: Species display complex behaviors that ensure reproductive success.

Content Limits: Evaluate the types of complex behavioral adaptations displayed by species to ensure

reproductive success. Complex behaviors may include migration, hibernation, schooling, territoriality,

mating rituals, feeding, etc. Concepts include innate and learned behavior, and how specific behaviors

affect reproductive success.

Introduction:

Animals exhibit a variety of behaviors, both learned and innate, that promote their survival and reproductive success in a variety of ways. Many behaviors have both genetic and learned components. Scientists study behavior and other aspects of organisms through observation and controlled experiments.Orientation behaviors place the animal in its most favorable environment. In taxis the animal moves toward or away from a stimulus. Taxis is often exhibited when the stimulus is light, heat, moisture, sound or chemicals. Kinesisis a movement that is random and does not result in orientation with respect to a stimulus. If an organism responds to bright light by moving away, that is taxis. If the animal responds to bright light by random movements in all directions, that is kinesis.

Pill bugs are terrestrial isopods that belong to the Phylum Arthropoda, Class Crustacea, which also includes shrimp and crabs. Most members of this group respire through gills.

Learner Objectives:

The student will be able to:

  • Write a hypothesis to predict the environment the pill bug will prefer(Do this before data collection begins)
  • Design and execute a controlled experiment to test a hypothesis about habitat choice by pill bugs
  • Make detailed observations of the organism’s behavior and included a detailed sketch
  • Describe the distribution of organism’s in a resource gradient
  • Determine if the observed behavior of movement is a kinesis or taxis

Materials:

(Based on class of 30 working in groups of 2)

  • 150 pill bugs (20 per group handed out in a stock Petri dish)
  • 60 plastic Petri dishes (4 per group) (Notch the bottoms of the four Petri dish bottoms and tape two together to make two choice chambers, Lids are used to prevent pill bug escape)
  • 60 filter papers cut to fit bottoms of Petri dishes (4per group)
  • 15 empty Petri dishes (one per group to place a sample of pill bugs in for observations)
  • 15 small containers of water with eye droppers
  • 15 soft brushes
  • magnifying lens

Procedure:

  1. Transfer 5 to 10 pill bugs from the stock culture Petri dishinto the empty Petri dish and observe for 10 minutes. Record observations on their general appearance, movements and interactions as they move about the Petri dish. Notice if they seem to prefer one area over another, if they keep moving, settle down, or move sporadically. Note any behaviors that involve 2 or more pill bugs. Try not to disturb
  2. Use a magnifying lens to see details of the organism. Draw a detailed sketch of one of the pill bugs. Return pill bugs to stock culture Petri dish.
  3. Now place filter paper into the bottoms of the 4 Petri dishes (two choice chambers). Be sure filter paper fits tightly to bottom of chamber so that the pill bugs can not crawl under the paper.
  4. Wet the filter paper for both sides of one choice chamber.Use an eye dropper to moisten the paper, it should be wet but without standing water. In the second choice chamber, wet one side leaving the other side dry.
  5. Set up a data table to record number of pill bugs on each side of the two choice chambers at 30 second time intervals.
  6. Use a soft brush to transfer 10 pill bugs into each of the two choice chambers. Place 5 pill bugs on each side of the choice chamber,(left and right sides). Cover the chambers.
  7. Count how many pillbugs are on each side of the choice chamber every 30 seconds for 10 minutes and record data. Continue to record even if they all move to one side or stop moving.
  8. Return pill bugs to the stock culture Petri dish.
  9. Graph both the number of pill bugs in the choice chamber that was divided into a wet side and dry side. Independent variable is placed on the X-axis and the dependent variable on the y-axis. Two lines will be drawn one showing number of pill bugs on the wet side and one showing the number of pill bugs on the dry side for each time interval.

Data Analysis, Conclusions, and Questions

  1. Write a hypothesis that predicts the environment the pill bugs will prefer.
  2. Identify the independent variable, dependent variable, and the chamber that was the control group and the chamber that was the experimental group?
  3. Were your results quantitative, qualitative or both? Explain your reasoning.
  4. Did the pill bugs show a preference for one environment over the other? Which environment? Give the data that supports this conclusion.
  5. Was the pill bug response to moisture best classified as kinesis or taxis? Explain your response.
  6. Where there any design problems with the experiment? If so, what was the problem and how might it be corrected.

References:

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