Using a Classification Key Lab

Using a Classification Key Lab

Discussion Suppose you find a large colorful wildflower while walking through the woods.

Chances are the flower has already been named and classified, but how can you learn its identify? As an aid to help others identify unknown organisms, biologists have developed classification keys.

Many classification keys have been developed to help identify wildflowers and many other kinds of plants and animals. Although these keys many vary in purpose and complexity, they have certain features in common. These classification keys are often called dichotomous keys. The word dichotomous comes form the word dichotomy , meaning "two opposite parts or categories." A dichotomous classification key presents the user with two opposite statements about some trait of an organism. By choosing the statement that best describes the unknown organism, the user is led to further pairs of statements. By going from one set of statements to another, the name of the organism or its classification group is finally determined. In this investigation you will use a classification key to identify several organisms.

Problem How can a classification key be used to identify organisms?

Directions Use the dichotomous key in figure #1 to determine scientific and common name

of each salamander in figure #2. Make sure that you write the scientific name and the common name of the salamanders the appropriate lines of the answer key.

Key to the Salamanders:

1 a Hind limbs absent

Siren intermedia

Siren

b Hind limbs present

Go to 2

2 a External gills present in adults

Neciturus macrolestus Mud puppy

b External gills absent in adults

Go to 3

3 a Large size (over 7 cm long)

Go to 4

b Small size (under 7 cm long)

Go to 5

4

a

Body background black, large white spots irregular Ambystoma in shape and size completely covering body & tail tigrinum

Tiger salamander

b

Body background black, small, round, white spots in Ambystoma

a row along each side fro eye to tip of tail

maculatum

Spotted Salamander

5 a Body background black with white spots

Go to 6

b

Body background light color with dark spots and or lines on body

Go to 7

6

a

Small white spots on a black background in a row along each side from head to tip of tail

Ambystoma Jefferson jeffersonianum salamander

b Small white spots on a scattered throughout a

black background from head to tip of tail

Plethodon glutinosus

Slimy salamander

7

a

Large irregular black spots on a light background extending from head to tip of tail

Ambystoma opacum

Marbled salamander

b No large irregular black spots on a light background

Go to 8

8

a

Round spots scattered along back and sides of body, tail flattened like a tadpole

Triturus viridescens

Newt

b

Without round spots and tail not flattened like a tadpole

Go to 9

Two dark lines bordering a broad, light mid-dorsal Eurycea

9 a stripe with a narrow median dark line extending

bislineata

from the head onto the tail

Two-lined salamander

b Without two dark lines running the length of the

body

Go to 10

A light stripe running the length of the body and Plethodon

10 a bordered by dark pigment extending downward on cinereus

Redbacked

the sides

salamander

b A light stripe extending the length of the body, a Hemideclylium Four-toed

marked constriction at the base of the tail

scutatum

salamander

Figure #2 Pictures of Unknown Salamanders

Using a Classification Key Write the scientific and common names of each salamander in Figure 1 on the line that corresponds to its number.

1. ________________________________________________ 2. ________________________________________________ 3. ________________________________________________ 4. ________________________________________________ 5. ________________________________________________ 6. ________________________________________________ 7. ________________________________________________ 8. ________________________________________________ 9. ________________________________________________ 10. ________________________________________________ 11. ________________________________________________

Question and Analysis 1. As you used the classification key to identify the salamanders, did you go from general to specific characteristics or from specific to general characteristics?

2. What two groupings do the scientific names of the salamanders represent?

3. Do you think that there may be some closely related species of organisms that cannot be identified with a classification key? Explain your answer.

4. Why do you think biological classification keys always present two, rather than some other number, of choices at each step?

5. What types of problems would scientists have today if Carolus Linnaeus had not developed his classification and naming system of organisms?

6. Explain what is meant by the statement, "Classification systems are the inventions of humans; diversity is the product of evolution."

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