The Scientific Method Isopod Lab
65 points
PLEASE DO NOT WRITE ON THIS HANDOUT. RECORD ALL DATA IN YOUR NOTEBOOK. INCLUDE HEADINGS, TITLES AND LABELS. WRITE THE QUESTIONS AND THEIR ANSWERS.
Objectives:
· Observe various aspects of a terrestrial isopod
· Design and conduct an investigation examining the responses of isopods to various environmental factors
Isopod Handling and Rearing
Raise isopods in a clear shoebox or similar, the bottom should be covered with soil or sand and kept moist (use a mister). An old piece of bark, and leaf litter should cover the soil. Isopods can be fed carrots, raw potatoes or apples (alternately fish flakes can be used as food). Moldy food or soil should be removed. Females can carry up to 200 eggs in a brood pouch underneath her abdomen and will remain in the pouch for about three weeks - they look the same as adults, only smaller.
Background Information
Terrestrial isopods are land dwelling crustaceans, commonly known as sowbugs or pillbugs (or rollypollys). They are related to lobsters, crabs, and shrimp and terrestrial isopods breathe with gills. While they look similar, sow bugs are different from pill bugs. Pill bugs will curl into a ball when threatened whereas sow bugs will attempt to flee. Since your isopods are caught from the wild, make sure you are using the same type for your experiments.
Ethology is the study of animal behavior. Many behaviors involve movement of the animal within its environment. In this exercise, you will investigate some innate (instincts) behaviors of isopods.
Orientation is a process by which animals position themselves with respect to spatial features of their environments. Taxis involves the turning of an animal's body relative to a stimulus - either toward or away. Kinesis is a random turning or movement of an animal in relation to a stimulus. Kinesis can be random, but its still a response to a stimulus – such as when a fly crawls faster or in circles in response to food placed nearby.
Isopod Observations & Sketch
Observe the animal as it explores its environment (Petri dish or lab table). Use a hand lens or microscope to examine details of the animal and make a scientific sketch.*
1. How do they seem to sense their environment? (1 pt)
2. Write 4 observations of them. (2 pts)
3. What are some stimuli they seem to respond to? (2 pts)
(Try seeing how they react to a pencil, a piece of paper over part of the Petri dish or air blown on them)
* Scientific Sketching
When you make a sketch of an animal, don't just draw an oval with a few squiggly legs - you are expected to do a scientific illustration similar to the sketch of an earthworm below.
Here are some tips for making an accurate sketch:
· Determine the relative proportions (length, width, height as well as lengths of body parts)
· Include the number of body segments, legs, antennae or any other appendages visible
· Label the anterior, posterior, dorsal and ventral sides
The Behavior Chamber
For the experiments you design, you will need to create a chamber to test the isopod’s reactions. Each basic chamber will consist of two sides, each side having a different environment, plus a tube that connects the chambers so that the isopods can move from one place to the other. You will be given the following materials, but the design of your chamber is up to you.
Materials – isopods, paper towels, plastic cups, straws, plastic bowls (or other things your teacher might provide for you). The same chamber can be used for multiple experiments.
Part A - Orientation of Isopods in Response to Moisture (25 points)
You will determine if isopods prefer a moist or a dry environment. To do this, you will set up your behavior chamber so that you have one side moist and one side dry (using paper towels). The dry side will be the control group and the moist side will be the variable that you are testing. By letting the isopods move about freely and counting how many are on each side, you can infer that they prefer whichever side they are on the most.
PLEASE DO NOT WRITE ON THIS HANDOUT. RECORD ALL DATA IN YOUR NOTEBOOK. INCLUDE HEADINGS, TITLES AND LABELS. WRITE THE QUESTIONS AND THEIR ANSWERS.
Problem: Write the problem that you are testing in the form of a question. (2 pts)
Hypothesis: Write a hypothesis in your notebook. Use the “If…, then….” format. (2 pts)
Procedure: Set up your behavior chamber as explained above. Transfer 4 isopods to each side of the chamber. Count and record the number of animals on each side of the chamber every 30 seconds for ten minutes, using a table like the one below.
DATA TABLE (8 points): Construct a Data Table like the one below in your notebook to record your data.
Time (min:sec) / # in Wet / # in Dry / Other Notes0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:50
4:00
4:30
5:00
5:30
6:00
6:30
7:00
7:30
8:00
8:30
9:00
9:30
10:00
Analysis Questions: Write the answers in complete sentences in your notebook.
1. What was the independent variable in this experiment? What was the dependent variable? What was the control group? (2 pts)
2. Create a histogram of your data in your notebook. Put time on the x-axis and number of isopods on the y-axis. (5 pts)
3. Based on your observations, do isopods prefer a moist or dry environment? Did this support or refute your hypothesis? (2 pts)
4. Suggest a reason why this behavior might be advantageous to an isopod. (2 pts)
5. Experimental Error is an error during an experiment in detection or measurement due to inadequate technique or the uneven application of measuring techniques. Describe at least two types of experimental error in this experiment. (2 pts)
Part B - Student Designed Experiment – As a group, select ONE of the following factors to investigate. You may have to bring in your own materials. See the teacher for more info. (30 points)
Factor / Materials (suggested)Temperature / cold pack, warm pack
Light / lamps, flashlights, dark construction paper, aluminum foil
pH / low pH (HCl), high pH (NaOH)
Substrate (surface) / soil, sand, sandpaper, bark, paper, cedar chips, gravel
Odor / Ammonia, acetone
Food / apple, potato, fish food, lunchmeat, etc.
Other Organisms / mealworms, crickets, earthworms
Problem: Write the problem that you are testing in the form of a question. (2 pts)
Hypothesis: Write a hypothesis in your notebook. Use the “If…, then….” format. (2 pts)
Procedure: Write your own procedure for the experiment. Make sure it makes sense! (5 pts)
Data Table: (8 points): Construct a Data Table like the one below in your notebook to record your data.
Fill in the top row with your chamber conditions (the factor you chose to test).
Time (min:sec) / CONTROL / Other Notes0:00
0:30
1:00
1:30
2:00
2:30
3:00
3:50
4:00
4:30
5:00
5:30
6:00
6:30
7:00
7:30
8:00
8:30
9:00
9:30
10:00
Analysis Questions: Write the answers in complete sentences in your notebook.
1. What was the independent variable in this experiment? What was the dependent variable? What was the control group? (2 pts)
2. Create a histogram of your data in your notebook. Put time on the x-axis and number of isopods on the y-axis. (5 pts)
3. Based on your data, write a conclusion paragraph explaining what happened in the experiment. Include whether you support or refute your hypothesis. Give a plausible reason why you think the isopods behaved the way they did. Include sources of experimental error. (6 pts)