NS 1021: Introduction to Biology: Organisms and the Environment

Lab: Hypothesis Testing: “Quattro variegatus” Predation

revised from Investigating Biology: A Laboratory Resource Manual, 4th ed.
by Donald P. French

Introduction

After a question has been asked about an observation, a scientist develops a hypothesis, an educated guess, about the question based on background knowledge, previous observation, or previous scientific work. Frequently, more than one hypothesis is formed, each of which might explain the observed phenomena. Once hypotheses have been formed, they must be tested. The scientist develops a procedure which has the possibility of showing a single hypothesis to be incorrect, or distinguishing between several hypotheses. For example, in the previous lab, the hypothesis that sunflower growth is stunted by road salt could have been shown to be incorrect by the experiment of growing sunflowers with various amounts of road salt.

In this lab you will be given a question and a hypothesis. You must develop one or more alternative hypotheses, then design an experiment which will distinguish between those hypotheses.

The Scenario

“Quattro variegatus” is a four sided, dorso-ventrally compressed species with disruptive coloration which lives communally in a highly patterned environment. Its only known predator is a large, bipedal, ambidextrous, mammal with binocular color vision.

A scientist observing this species notes that the largest Q. variegatus are disappearing at an alarming rate. After observing predation techniques and examining the stomach contents of the predator, she finds that the larger individuals are eaten more frequently than the smaller ones. When she samples populations, she does not find equal numbers of all sizes. Her hypothesis is that larger individuals are eaten more frequently than smaller ones because they are more readily seen. Is she correct?

Procedure

With your partner, develop one or more alternative hypotheses to explain the given observations.

Design an experiment which will distinguish between your hypotheses (including the one of the scientist above).

Carry out your experiment:

Collect data
Analyze your data: does your data support the scientist’s hypothesis, or one of your alternative hypotheses?

What would be your next step?

If you have time, carry out your proposed next step.

Lab Report

Title: a few words which suggest the purpose of the lab.
Minus 1 point if no title

Introduction: What is the purpose of this lab? (hint: it is not just to learn something about an imaginary organism) Summarize, in your own words, the scenario. Include the given hypothesis.
2 pts.

Hypotheses: State your alternative hypothesis or hypotheses.
2 points

Experiment: Describe your experimental procedure and why you designed it that way. Include any preliminary observations you made which led to your experimental design.
3 points

Data: report your data in an organized fashion which allows the reader to understand your results. This may be in the form of a table, graph, or simple list.
2 points

Conclusions: Is the scientist’s hypothesis correct? Why or why not? Is one of your hypotheses more likely to be correct? Why or why not?
3 points

Next steps: What would you as a scientist do next? Include any subsequent hypotheses you formed after doing your experiment.
2 points

Metacognitive Analysis: What aspects of this lab increased your understanding of the scientific process? Were any parts of this lab confusing or unhelpful? What would you change?
1 point