Episode Two Debriefing: Teacher Guide
THE KEY TO IT ALL
In this activity, the student will learn why scientists
classify living things and create a classification key.
Background
Taxonomy is the science in which living things are named and classified in an orderly
manner according to how they are related. The modern system of classification is based
on the work of an 18th century Swedish scientist, Carl Linnaeus. Linnaeus divided all
living things into two broad categories (taxa) called kingdoms. He based these categories
on the characteristics that the living things shared.
Linnaeus’ system also assigned each organism a two-part Latin scientific name. The first
part of the name is the genus to which the organism belongs, and the second part is the
species name. For example, the scientific name of humans is Homo sapiens. The reason
for using scientific rather than common names is that common names can be a source of
confusion. They vary by region; therefore, one organism may have several common
names. Furthermore, two different organisms can have the same common name.
To identify an organism, scientists often use a dichotomous taxonomic or classification
key. In Episode Two of “A Plaguing Problem,” a botanical taxonomic was used to
identify the mystery plant as Papaver somniferum. A dichotomous key is made up of
pairs of descriptions. By deciding which description in the pair pertains to the specimen,
the user is then led to another pair of descriptions or to the name of the organism.
Sample Key Section
1. If the flower has one ovary---------------------------------------Go to 2
1. If the flower has more than one ovary----------------Rosa bracteata
2. If the flower has four stamens-----------------------------------Go to 3
2. If the flower has more than four stamens----------------------Go to 4
The Reconstructors
16
Ancient Alarm Activity 2.3
Episode Two Debriefing: Teacher Guide
Learning Objectives
The student will:
• Know why scientists classify living things.
• Create a dichotomous classification key.
Materials
•
•
The Key to It All Student Activity Sheet
bags with at least five small, related objects
Procedure
1.
Prior to class make up bags containing at least five related objects. Suggested
objects are an assortment of buttons, small hardware (nuts, screws, nails, etc),
writing instruments.
2.
Select a number of students to come to the head of the class. Divide this group
of students into two groups based on a physical characteristic such as gender or
eye color.
3.
Have the class guess which characteristic you used to separate the students into
groups. Relate this student classification exercise to the science of taxonomy.
4.
Describe the purpose of a dichotomous classification key. Use the objects and
the key on the Potent Plants Student Activity Sheet to explain how a key works.
Prompt students to come up with other traits that could have been used to make
the key. Examples are color (solid black versus black border) and presence or
absence of writing on the object.
5.
Inform students that Beta needs them to create a dichotomous key of some
objects at ORB. Divide the class into pairs of students. Give each pair a bag of
objects, and have the students come up with a classification key which includes
each item. The students should then record their key on the student activity
sheet.
Extension Activities
•
•
•
•
Science: Investigate how DNA is used in modern classification.
Geography: Research how the common names of several American plants vary by
region.
History: Research the history of taxonomy.
Visual Arts: Create a phylogenetic tree of the plant kingdom as a mobile.
The Reconstructors
17
Ancient Alarm Activity 2.3
Episode Two Debriefing: Teacher Guide
Standards
National Science Education Standards, Grades 5-8
•
Science Content Standard A: All students should develop abilities necessary to do
scientific inquiry.
Books
•
•
Campbell, N. A. 1993. Biology. Redwood City: Benjamin/Cummings Publishing
Company.
National Research Council. National Science Education Standards.
Washington, DC: National Academy Press, 1996.
Web Site
Carl Linnaeus: The father of modern plant and animal classification
http://www.linnean.org
The Reconstructors
18
Ancient Alarm Activity 2.3
Episode Two Debriefing: Student Activity Sheet
THE KEY TO IT ALL
A taxonomic or classification key notes
similarities and differences between objects.
Beta wants you to create a dichotomous
classification key of some objects from ORB.
Materials
•
bag of objects.
Procedure
1. Review with the class the dichotomous classification key to the objects below:
Help
1. If the object has three sides………………………..…..Triangle
1. If the object has more than three sides…….……...……Go to 2
2. If the object has four sides …………………………….Go to 3
2. If the object has more than four sides………………….Go to 4
3. If the object’s sides are the same length.…………..……Square
3. If the object’s sides are different lengths………….…Rectangle
4. If the object has eight sides…………………………....Octagon
4. If the object has more than eight sides………………….….Star
The Reconstructors
19
Ancient Alarm Activity 2.3
Episode Two Debriefing: Student Activity Sheet
Name:
Class:
Date
The Key to It All
Procedure (cont.)
2. Make a dichotomous classification key of your bag of objects. Give the key a title.
Write the key in the space below the title.
Title: Dichotomous Classification Key of _____________________ (type of objects).
The Reconstructors
20
Ancient Alarm Activity 2.3