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Cladistics is one way scientists classify organisms.
A cladogram shows the nature of evolutionary
relationships that may have occurred, similar to
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family tree. You will make a cladogram in this activity.
Procedure
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Part
0uestions
Write your answers 0n a separate sheet of paper.
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Display your set of hardware organisms and match
each one to the organisms listed on your Hardware
)rganism Key actiuity sheet. Make sure you have all
the organisms Iisted.
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Classify your hardware organisms into groups. 0n
a
separate sheet of paper, make a record of your
classifications, Iisting the letter for each organism you
have classified. Then list the common characteristics of
each of your groups.
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Part Il
You
will now use a different method to classify your
organisms. Follow the instructions onlhe Cladogram
Easrcs activity sheet 1o create your cladogram.
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After you have created and revised a r:ough draft of
your cladogram, create a final version to share with the
cl a ss.
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When you have completed your cladogram, answer
the questions.
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Compare your cladogram with others in the class. Will
all correct cladograms be the same? Why or why not?
Compare cladistics with the more traditional taxonomy
that you did in the Part I of the lesson. How do they
differ? What are the advantages and disadvantages of
each method?
Hardware Organism KeY
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ln cladistics, similar characteristics that come from
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To make a cladogram, scientists
comm0n ancestor are used t0 divide organisms into
groups. A cladogram
will begin
first collect data
on
the features of all the organisms they hope to classify.
by grouping organisms
This data is then analr4ed to determine which character-
based on a characteristic displayed by all the members
istics were present in what could have been a common
of the group. Subsequently, the larger group, or clade,
ancestor and which might have been developed in
will contain increasingly smaller groups (clades) that
share the traits of the clades before them. but also
later times. Use the following instructions to make
a
cladogram for your set of hardware organisms.
exhibit distinct changes as the organism evolves.
The example that follows represents a cladogram.
Procedure
@ tvtake your cladogram
0n a separate sheet of paper.
Lay out your organisms on a work surface. List all the
characteristics you see for each object and make
a
table of all the traits.
@ Wnicfr
characteristic do all the objects have in
common? This is referred to as a primitive, or original,
characteristic. lt is of little value in analyzing the
relationships within a group since all members possess
this characteristic.
@ Again look at the data to determine
hair
I d e ri v ed ch ara
common
characteristics that only a portion of the group
cte ri st i c )
has. These are referred
to as derived, or advanced,
characteristics. They are usually more advanced
limbs
( d e riv e
features that were added to the primitive features
d c h ara cteri sti c )
found earlier. The largest group of these derived
characteristics
laws
( de r i v e
will
be the first to branch from the
main trunk of the cladogram. Name the derived
d c h a ra cte risti c )
characteristic and list all the objects that have that
characteristic. Your drawing of the cladogram at
this point should look similar to the following:
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Sample Cladogram
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(pri m it ive cha ra cteristi c)
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characteristic
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Look for further characteristics
that are common to only
a portion of the group and add these to the cladogram
until the graups can be sorted no further.
Source: Science al a 0istance-*Professor John Blamire
{M.brmklyn.cuny.edu/bclahp/CLAS/CLAS.Clad.html
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