How do you find similar
heritable characteristics?
Phylogenetic mapping will help you
answer our initial question: are birds
and dinosaurs related?
Created by K. Snyder as part of a project for
Seminars in Science Class: The Link
between Birds and Dinosaurs
What is phylogenetic mapping?
• It is a way to
at organisms that focuses on
patterns of similarity among heritable characteristics.
• These characteristics include such things as bone
structure, muscle anatomy, color patterns, intrinsic
behavior, and DNA sequence.
• Remember, we need to keep our goal in mind as we
do this. Do we see similarities between dinosaurs and
birds?
• Let’s look at an example
– Think back to our study of the members of Kingdom
Animalia
– We’ll limit our focus on the characteristic of “limb
structure.”
Vertebrate Tetrapods
• Every animal in the group we have selected is
a vertebrate and also a tetrapod.
– A tetrapod is a vertebrate who possesses limbs
equipped with hands and feet. (tetra = 4, pod =
foot)
• Of the following organisms, which reproduce
by means of an egg with an amnion?
– Salamanders, crocodilians, lizards, humans, and
birds.
– We will find out using by creating a cladogram.
Compare these two organism based
on their limb structure
Shark
Lizard (Komodo Dragon)
Compare these two skeletons.
• Are these vertebrates?
• Do they have tails?
• How many limbs do they have?
• The lizard is a tetrapod, and the shark is
not.
Now, compare crocodiles and birds
Crocodile
• How many limbs does each vertebrate
have?
• These are both tetrapods, as is the lizard
on the previous slide.
Bird
This is a cladogram & provides another way of
looking at the information we have been discussing
We next look at
amniotic eggs.
We looked at
limbs.
Let’s recap
• In the example, we were reminded that all
vertebrates possess a backbone, or endoskeleton.
• Not all, however, possess limbs.
• Of those who possess limbs (four limbs to be
exact), only some reproduce by means of an
amniotic egg.
• What does this show? That birds, crocodiles,
lizards, and humans are more closely related to
each other than they are to salamanders and
sharks.
Why is that important?
• We are trying to determine if birds and dinosaurs
are related.
• We need to look at the heritable features of
dinosaurs, and where they fit on the cladogram
we just viewed.
• Ask yourselves these questions:
–
–
–
–
Are they vertebrates?
How many limbs do they have?
Are they amniotes?
Is there fossil evidence of their nesting behavior?
Where do we go from here?
• More specific focus on characteristics to hone in
the cladogram.
–
–
–
–
–
–
–
–
Shape of the neck and vertebrae that comprise this
Body position and orientation
Pelvic structure and orientation
Tail structure
“hand” and “foot” structure”
Behaviors
Feathers
…..
References
• Dingus, L. Rowe, T. The Mistaken Extinction.
New York: W. H. Freeman, 1998.