Name:
Hope
Date:
Student Exploration: Dichotomous Keys
Directions: Follow the instructions to go through the simulation. Respond to the questions and
prompts in the orange boxes.
Vocabulary: dichotomous key, genus, organism, scientific name, species, traits
Prior Knowledge Question (Do this BEFORE using the Gizmo.)
Jerome is walking through a park when he sees the spider shown at left. How could
Jerome find out what type of spider it is?
He could look at the characteristics of the spider.
Gizmo Warm-up
In the field, scientists often have to identify an unfamiliar organism (living
thing). A reliable way to identify organisms is to use a dichotomous key.
A dichotomous key is a series of paired statements or questions that lead
to the identification of an organism.
The Dichotomous Keys Gizmo allows you to use five different dichotomous
keys to identify a variety of organisms. To begin, make sure California
Albatrosses and Organism A are selected.
1. Read the two statements at lower right. Which of the two statements most closely matches the
characteristics of the bird pictured?
the large areas of the bird's body is covered in feathers
2. Select that statement and click Next. Continue until you have correctly identified the albatross. If you
change your mind about a choice, you can click the Back button. If you incorrectly identify the albatross,
you can click the Start Over button and try again.
A. What is the name of the albatross?
Short-tailed albatross
B. The scientific name is shown in italics. Scientific names have two parts: the genus name and the
species name. What is the scientific name of this albatross?
Phoebastria albatrus
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Activity A:
Use a
dichotomous key
Get the Gizmo ready:
● Make sure the California Albatrosses key is
selected.
● Select Organism B.
Introduction: As you saw on the previous page, a dichotomous key can help you identify an organism using
its characteristics, or traits. The keys in this Gizmo use only physical traits, such as feather color, to identify
organisms. In some cases, behavioral traits are used in dichotomous keys. For example, some frog species
can be identified by their croaks.
Goal: Use a dichotomous key to identify albatross species found in California.
1. Compare: Take a close look at organism B.
A. How does organism B differ from organism A?
This bird's body is mostly covered in grey or black feathers, with light-coloured feet.
B. What physical traits do you think can be used to help identify organism B?
The colour of its feathers, the shape and colour of its beak, and the colour of its feet
2. Identify: Use the Gizmo to identify organism B. Then, identify the other albatrosses included in the
California Albatrosses key. Complete the table below.
California Albatrosses
Organism
Common name
Scientific name
A
Short-tailed albatross
Phoebastria albatrus
B
Light MantledAlbatross
Phoebetria palpebrata
C
Shy albatross
Thalassarche Cauta
D
Wandering albatross
Diomedea Exulans
E
Laysan albatross
phoebastria immutabilis
F
Black-footed albatross
Phoebastria nigripes
3. Think and discuss: What do you think are some limitations of dichotomous keys?
One of the disadvantages, I believe, is the traits that they provide can be used to identify
the organism, which can lead to confusion. only physical traits are used
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Activity B:
Identification
practice
Get the Gizmo ready:
● Select the Canadian Rockies Buttercups key.
● Select Organism A.
Introduction: Dichotomous keys are written for small, specific groups of organisms. For example, each
dichotomous key in this Gizmo is used to identify six to eight related species found within a geographic region.
Goal: Identify a variety of organisms using dichotomous keys.
1. Practice: Use the Gizmo’s dichotomous key to identify all the buttercups.
Organism
Canadian Rockies Buttercups
Common name
Scientific name
A
Meadow Buttercup
Ranunculus acris
B
White Water Crowfoot
Ranunculus aquatilis
C
Alkali Buttercup
Ranunculus cymbalaria
D
Alpine Buttercup
Ranunculus eschscholtzii
E
Macoun’s Buttercup
Ranunculus macounii
F
Dwarf Buttercup
Ranunculus pygmaeus
2. Analyze: Which traits were used to identify the flowers, and which of these traits did you think were most
useful?
Colors, Leaf shapes, and stem sizes.
3. Practice: Select the Texas Venomous Snakes key. Use the Gizmo’s dichotomous key to identify all the
snakes.
Texas Venomous Snakes
Organism
Common name
Scientific name
A
Western diamond back rattle snake
Crotalusatrox
B
Scarlet king snake
Lampropeltis elaspsiodes
C
Copperhead
Agkistrodon contortrix
D
Western massasauga rattlesnake
Sistrurus canteriatus
E
Cotton mouth
Agkistrodon piscovorus
F
Timber rattlesnake
Crotalus horridus
G
Coral snake
Micrusus tener
4. Reflect: Why is it important to be able to tell a scarlet kingsnake apart from a coral snake?
Because they are so similar, and to avoid confusion, the scarlet king snake is considered to
be harmless.
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5. Practice: Select the Virginia Evergreens key. Use the Gizmo’s dichotomous key to identify all the trees.
Virginia Evergreens
Organism
Common name
Scientific name
A
Northern White Cedar
Thujaoccidentalis
B
Loblolly Pine
Pinus taeda
C
Norway Spruce
Picea abies
D
Eastern Hemlock
Tsugacanadensis
E
Dawn Redwood
metasequoiaglyptostroboides
F
Bald Cypress
Taxodium distichum
G
Eastern White Pine
Pinus Strobus
H
Virginia Pine
Pinus Virginiana
6. Practice: Select the Florida Cartilaginous Fishes key. Use the Gizmo’s dichotomous key to identify all the
fishes.
Florida Cartilaginous Fishes
Organism
Common name
Scientific name
A
Blacktip Shark
Carcharhinus lilmbatus
B
Carcharhinus lilmbatus
Dasyatis americana
C
scalloped Hammerhead
sphyma lewini
D
Sandbar Shark
Carecharhinus plumbeus
E
Shortfin Mako
Isurus oxyrinchus
F
Bonnethead Shark
Sphyma tiburo
G
Atlantic Stingray
Dasyatis sabina
H
Clearnose Skate
Raja eglanteria
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Activity C:
Get the Gizmo ready:
Make your own
dichotomous key
● Select the California Albatrosses key.
Goal: Make a dichotomous key.
1. Observe: Now that you’ve learned how to use a dichotomous key, you get to practice making your own.
We’ll start with four organisms you’ve already seen:
Short-tailed albatross
Shy albatross
Wandering albatross
Laysan albatross
A. What is one trait that could be used to separate these albatrosses into two groups of two birds
each? (Hint: Look at the colors and patterns on their plumage and beaks.)
Solid black feathers, white and black mixed feathers.
B. Use this trait to write statement set #1 in the table below. The statements should be mutually
exclusive. In other words, either the albatross has that trait or it doesn’t.
C. Observe the albatrosses described by statement #1a. Identify one trait that could be used to
differentiate these organisms and use it to write statement set #2. Repeat this step for the
albatrosses described by statement #1b.
Set
1
2
3
Statements
Identity of Organism
a. yellow head
Go to #2
b. yellow tip beak
Go to #3
a. white feathers
Short-tailed albatross
b. gray tip beak
Laysan albatross
a. spotted feathers
b. pink foot
Shy albatross
Wandering albatross
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