Levasseur
Using and Making a Biological Key
Classification is a way of separating a large group of closely related organisms into smaller subgroups.
Classification makes everyday life easier by putting organisms in a useful system. Classification helps us to
group the organisms we live with every day. Classification also lets us have a system for reference and will
continue to help as we study the organisms around us. The scientific names of organisms are based on the
classification systems of living organisms. To classify an organism, scientists often use a taxonomic key that
lists specific characteristics, such as structure and behavior, in such a way that an organism can be identified.
Essential Question: Will you be able to organize a list of 14 sharks using a taxonomic key?
Hypothesis: If I follow the taxonomic key, I will be able to identify the 14 pictured sharks.
Materials: Ruler, Shark data sheet, taxonomic key, paper, pencil
Procedure:
1. Use the figure below as a guide to the shark parts used in the taxonomic key on the next page.
2. Read sentences 1A and 1B of the key then study Shark 1 on your data sheet. Follow the directions in
the sentences and continue until you determine the family name of the Shark.
3. Continue this process for each shark on the data sheet until you have identified the family for all of
them.
Taxonomic Key – Sharks
1. A. Body kite-like in shape when viewed from the top………………………………………………………….…..Go to #12
B. Body not kite-like in shape…………………………………………………………………………………………………….Go to #2
2. A. Pelvic fin absent and nose is saw-like…………………………………………………………..…..Family Pristiophoridae
B. Pelvic fin is present………………………………………………………………………………………………………….……Go to #3
3. A. Six gill slits………………………………………………………………………………………..…………………Family Hexanchidae
B. Five gill slits…………………………………………………………………………………………………………………………..Go to #4
4. A. Only one dorsal fin………………………………………………………………………………….….……..Family Scyliorhinidae
B. Two dorsal fins…………………………………………………………………………………………….………………………..Go to #5
5. A. Mouth positioned at front of head rather than along the underside…………....Family Rhinocodontidae
B. Mouth along underside of head………………………………………………………………………………….….……..Go to #6
6. A. Head expanded on side with eyes at the ends of the expansion……………………………..Family Sphyrnidae
B. Head not expanded…………………………………………………………………………………………….…………………Go to #7
7. A. Top half of caudal fin is exactly the same size and shape as bottom half………….…………Family Isuridae
B. Top half of caudal fin is different in size and shape than bottom half…………………………………...Go to #8
8. A. First dorsal fin is very long, almost half the total length of the body………….…..Family Pseudotriakidae
B. First dorsal fin regular length………………………………………………………………………………………..………Go to #9
9. A. Caudal fin is very long, almost as long as the entire body………………………………………...Family Alopiidae
B. Caudal fin regular length………………………………………………………………….………………………………….Go to #10
10. A. A long needlelike point on end of nose………………………………….…….……………Family Scapanorhynchidae
B. Nose without a long point…………………………………………………………………..……………………………….Go to #11
11. A. Anal fin absent……………………………………………………………………………………..…………………..Family Squalidae
B. Anal fin present…………………………………………………………………………………………….….Family Carcharhinidae
12. A. Small dorsal fin present near tip of tail…………………………………………………………………………Family Rajidae
B. No dorsal fin present near tip of tail……………………………………………………..………………………….….Go to #13
13. A. Front of animal has two hornlike appendages…..…………………………………………….………Family Mobulidae
B. No hornlike appendages………………………………………….……………………………………………..Family Dasyatidae
Analysis:
1.
2.
3.
4.
5.
What is a taxonomic key and how is it used?
List four different characteristics or traits that were used in the shark key.
What main trait could be used to separate shark #4 from shark #8?
What main trait could be used to separate shark #4 from shark #7?
What main trait could be used to separate shark #5 from shark #12?
6. Make your own taxonomic key for the leaves below following the same format as for the sharks and
birds. Design the key to classify each leaf family.
A
F
B
G
C
H
D
I
E
J
7. Prepare your own key for the four birds pictured below. Use the same format as was used for the
sharks. Your key should correctly use traits to lead to each individual bird family.
Conclusion:
Use your rubric.