Week of September 12, 2022
Unity Lab 3 Activity
Overview
Today, you will:
● Develop a hypothesis about planarian behavior
● Design a controlled, independent samples experiment
● Design and set up a controlled, paired samples experiment
● Collect data from your paired samples experiment
● You will keep this packet for your records, and use it to complete an assignment due next week
SET UP AN EXPERIMENT ON PLANARIA BEHAVIOR (PART 1): HYPOTHESIS AND PREDICTION
Scientists use their own observations, existing data, and logic to develop testable hypotheses about the
world. They then test these hypotheses, and based on the results of their tests, either support their
hypotheses, or reject them, and develop new hypotheses.
CHEMOTAXIS: EXISTING SCIENTIFIC DATA
● Chemotaxis is the movement of an organism in a
direction corresponding to a gradient of
increasing or decreasing concentration of a
particular substance.
● Planaria have two auricles (earlike projections) at
the base of the head, which are sensitive to
touch and the presence of certain chemicals.
● Planaria eat living or dead small animals that
they suck up with their muscular mouths. Food
passes from the mouth through the pharynx into
the gastrovascular cavity where it is digested by
the cells lining the cavity. Then its nutrients
diffuse to the rest of the planaria. Egg is
provided in this lab, if you wish to test movement towards a food source.
o An example of an experiment that tests chemotaxis towards egg is testing the amount of
time it takes for each planarian to swim to the region of a plate that contains a food
molecule
YOUR OBSERVATIONS
Put down any existing observations of planaria behavior that is informing your hypothesis
YOUR HYPOTHESIS
Using existing data, and your logic, come up with a hypothesis about planaria behavior. Remember,
hypotheses have explanatory power.
Page 1
YOUR PREDICTION
Based on your hypothesis, write a prediction. Get this prediction ok’d by your instructor or teaching aide.
2. DESIGN A CONTROLLED, INDEPENDENT SAMPLES EXPERIMENT
DEVELOP A PROTOCOL TO TEST YOUR PREDICTION
Some things to consider before you develop your protocol.
● This is an experiment, so there has to be a control.
● This is a paired samples experiment.
● An easy way to test planaria movement is by putting a piece of graph paper under the petri dish, and
counting the number of squares the planaria swim past in the allotted time.
● You can only observe 1 organism at a time well, so you will most likely do trials of your experiment, 1
organism at a time.
● Planaria put in new environments can act strange until they settle down. Give each planarian 1
minute of acclimation time before you start your data collection.
● You have available to you
o Petri dishes
o Graph paper
o Stop watches
o Egg yolk
o About 20 planaria
● IMPORTANT: Because of the nature of the assignment you will do this week, you need to collect
DISTANCE or TIME based data (for example, how many squares does the planarian pass through to
get to a particular square on the grid; or how long does it take a planarian to reach a square or
group of squares?)
BRIEFLY DESCRIBE YOUR PROTOCOL
Get this protocol ok’d by your instructor or teaching aide.
1.
2.
3.
4.
5.
6.
2. Now describe how you would change your protocol to make it an INDEPENDENT SAMPLES
EXPERIMENT
RECORD DATA FROM YOUR PLANARIA EXPERIMENT (PAIRED SAMPLES)
*Data is used in your assignment*
Planaria
Control
Movement
Planaria
with Egg
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
10
10
Movement
REFERENCES
University of California Museum of Paleontology (UCMP) a. Understanding Science. “What is science?”
Copyright 2020, Accessed 14 May 2020. Internet. Available from:
https://undsci.berkeley.edu/article/whatisscience_01.
REVISION HISTORY: RJS 2020; SY 2021 & 2022