Yakima WATERS Mini Lesson
Classification of Life: Using a Dichotomous Key
Targets and Assessment
WA Science Standards Addressed:
 Science 9-11 LS3E
 Science 9-11 LS3D
 Science 9-12 INQA
Lesson Parameters
Content Area: Biology
Overview: Life forms are classified into groups based on
similarities and differences. Students must work together to
organize a list of phyla characteristics and apply them to a
cladogram and create a dichotomous key to the animal
kingdom.
Grade Level: 9-11
Assessments:
 Group assessment: points awarded for each of the
20 characteristics that are correctly applied to the
appropriate cladogram arm (out of 20 points) with
opportunity for bonus point if teacher can use
students’ key to identify a mystery phylum.
Suggested Time: ~55 minutes
Special Materials:
 Poster board or white board
 Lists of animal phyla characteristics
Learning Outcomes:
Knowledge: Students will apply characteristics to design a dichotomous key and use it to solve a mystery phylum
Skill: Students will be able to construct a useable dichotomous key to the animal kingdom.
Science Concept Background:
Biological classification is the traditional grouping and categorizing of living organisms according to shared physical characteristics.
All living things can be sorted into groups of progressively finer levels of resolution, and all organisms within a group are related in
some way. More recently, molecular data has lead to the revision of many traditional groupings to reflect the Darwinian principle of
common decent, creating monophyletic groupings.
6-8 LS3G
Evidence for evolution includes similarities among anatomical and cell structures, and patterns of development
make it possible to infer degree of relatedness among organisms.
6-8 APPD
The process of design begins by defining a problem and identifying criteria for a successful solution and
brainstorming to arrive at potential solutions.
6-8 APPE
Scientists and often work together to generate creative solutions to problems and decide which ones are most
promising.
6-8 APPF
Solutions must be tested and results are used to modify the design.
Materials:
Flip chart or whiteboard and overhead document camera
Procedure:
Reflect on the dichotomous key lesson with key to aliens (below). As a class key out alien #20 using document camera (5 minutes).
Ask students to list the things that are common to all living things aloud while instructor writes these things down on flip chart/white
board which should include (5 minutes):
 DNA
 Cells
 Obtain and use energy
 Reproduce
 Grow
 Maintain homeostasis
 Interact and adapt to environment
Have students break into groups of 3-4 and provide them with a list of characteristics (underlined key phrases in animal kingdom key
below) that they are to match with phylum branches using their poster/white board. They can use their notes and computers and
even ask instructor “how many do I have right” during the lesson (15-20 minutes). Each group will then construct a key modeled
after alien key (20 minutes) Instructor will then go to each group with a pre-selected phylum in mind and see if the group can
discover the phylum using their key and asking instructor key questions at each split of their key (5 minutes).
Key questions:
What characteristics are used to group animals into phyla?
How can these characteristic be used to create a dichotomous key?
How can a dichotomous key be used to identify an unknown animal?
Extension(s):
Have students add classes (that were addressed as beasts) and class characteristics to their cladogram.
Teaching Tips:
Some student may just want to keep rearranging characteristics and asking instructor how many they have right. If students abuse
this resource there may need to be a limit on the number of times they can ask.
Supplements:
Tree of Life: Web Project Retrieved November 16, 2009 from http://tolweb.org/tree/phylogeny.html
Dichotomous Key for the Animal Kingdom. Retrieved November 16, 2009 from
http://home.bresnan.net/~jabbas2/LessonPlans/Chap18/AnimalKey2006.pdf
Alien Dichotomous Keys
1.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
a. The creature has a large wide head...................go to 2
b. The creature has a small narrow head...............go to 11
2.
a. It has 3 eyes ......................................................go to 3
b. It has 2 eyes .....................................................go to 7
3.
a. There is a star in the middle of its chest...........go to 4
b. There is no star in the middle of its chest ........go to 6
4.
a. The creature has hair spikes ............................Broadus hairus
b. The creature has no hair spikes........................go to 5
5.
a. The bottom of the creature is arch-shaped .......Broadus archus
b. The bottom of the creature is M-shaped ..........Broadus emmus
6.
a. The creature has an arch-shaped bottom ..........Broadus plainus
b. The creature has an M-shaped bottom..............Broadus tritops
7.
a. The creature has hairy spikes ...........................go to 8
b. The creature has no spikes................................go to 10
8.
a. There is a star in the middle of its body ...........Broadus hairystarus
b. The is no star in the middle of its body ............go to 9
9.
a. The creature has an arch shaped bottom ..........Broadus hairyemmus
b. The creature has an M shaped bottum .............Broadus kiferus
10. a. The body is symmetrical .................................Broadus walter
b. The body is not symmetrical............................Broadus anderson
11. a. The creatrue has no antennae ..........................go to 12
b. The creature has antennae ..............................go to 14
12. a. There are spikes on the face ...........................Narrowus wolfus
b. There are no spikes on the face ......................go to 13
13. a. The creature has no spike anywhere ...............Narrowus blankus
b. There are spikes on the right leg ....................Narrowus starboardus
14. a. The creature has 2 eyes...................................go to 15
b. The creature has 1 eye....................................Narrowus cyclops
15. a. The creature has a mouth................................go to 16
b. The creature has no mouth..............................go to 17
16. a. There are spikes on the left leg ......................Narrowus portus
b. There are no spikes at all ...............................Narrowus plainus
17. a. The creature has spikes ..................................go to 18
b. The creature has no spikes ............................Narrowus georginia
18. a. There are spikes on the head ........................go to 19
b. There are spikes on the right leg....................Narrowus montanian
19. a. There are spikes covering the face ..................Narrowus beardus
b. There are spikes only on the outside edge of head ...Narrowus fuzzus
Animal Phylum Key
la. The animal is very simple with a body that is quite porous, it is aquatic and a filter
feeder, internal skeleton made of spongin, carbonate or silicate spicules.......................................................... Phylum Porifera
lb The animal is not like the statement in la ........................................................................................................................ go to 2a
2a. The animal is strictly aquatic with tentacles and stinging cells, radial symmetry is present.............................Phylum Cnidaria
2b. The animal is not like the statement in 2a .................................................................................................................... go to 3a
3a. The animal is worm-like but not snake-like ................................................................................................................... go to 4a
3b. The animal is not worm-like .......................................................................................................................................... go to 6a
4a. The animal appears as a flattened worm, it is triploblastic; acoelomate, it has a
mouth but no anus; it has a two way digestive tract .............................................................................. Phylum Platyhelminthes
4b. The animal is not like the statement in 4a ..................................................................................................................... go to 5a
5a. The animal is a smooth-bodied worm; triploblastic, body cavity is a pseudocoelom;
it has a complete digestive tract with mouth and anus ................................................................................... Phylum Nematoda
5b. The animal is a segmented worm with a true body cavity called a coelom; it has a
complete digestive tract with one way traffic, both mouth and anus are present ............................................. Phylum Annelida
6a. The animal lives in salt water; its body is typically five-part radial symmetry; it moves
with many tube feet ............................................................................................................................... Phylum Echinodermata
6b. The animal is not like the statement in 6a ...................................................................................................................... go to 7a
7a. The animal has a soft body usually with some type of shell or tentacles with suction cups; muscular foot; adults have
bilateral symmetry............................................................................................................................................ Phylum Mollusca
7b. The animal is not like the statement 7a ......................................................................................................................... go to 8a
8a. The animal has an exoskeleton made of chitin; the legs are jointed; open circulatory
system is present .......................................................................................................................................... Phylum Arthropoda
8b. The animal has or had a notochord and gill slits when it was developing as an embryo;
an endoskeleton is usually present; a dorsal nerve cord originates from a head
region .............................................................................................................................................................. Phylum Chordata
Author: Michelle Lester, Yakima WATERS Project, CWU, Fall 2009