Pre-Lab: Dichotomous Keys
Problem Can you construct a dichotomous key that can be used to identify organisms?
Materials reference materials
Lab Manual Chapter 18 Lab
Skills Focus Observe, Classify, Compare and Contrast, Sequence
Connect to the Given the enormous variety of life on Earth, not even experts can identify every organism they observe. Both experts and amateurs use dichotomous keys to identify organisms. These keys are based on the appearance of organisms. A key is a series of paired statements. Readers select the statement that best describes an organism at each step until the organism is identified and named. In this lab, you will practice using a dichotomous key. Then you will construct your own key for a group of organisms.
Review Why do biologists prefer to identify an organism by its scientific name?
Compare and Contrast Explain how the way modern biologists group species into larger categories is different from the system that Linnaeus used.
Review How many choices does a dichotomous key provide at each step?
Preview the procedure in the lab manual.
Observe Name three different physical traits that are used in the shark dichotomous key.
Classify Do all the sharks you will try to identify belong to the same genus? Explain your answer.
Apply Concepts After you make a list of physical traits that you can use in your dichotomous key, how will you decide which trait to pick for the first step?
Visit Chapter 18 online to test yourself on chapter content and to find activities to help you learn.
Untamed Science Video Hop on board with the Untamed Science crew to find out how organisms are classified.
Art in Motion View a short animation that explains how to use a dichotomous key.
Art Review How well do you know the characteristics of the three domains? Test yourself in this activity.
InterActive Art Build your understanding of cladograms with this animation.
Data Analysis Investigate the problems involved in finding a mate for Lonesome George—the sole living member of his Galápagos tortoise species.