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NOVA
pogen
NOVALABS
The Evolution Lab
MISSION 2
Eating dinosaurs for dinner: Has anyone ever told you that dinosaurs aren't extinct? It's true! They aren't. But how
can that be? There are no T. rexes at the zoo, or Triceratopses roaming the plains. This level holds the
key to
understanding where today's dinosaurs are hiding-on our farms, in
the trees, and on our
dinner plates. Answer
questions 3-5 below before you move on to the next level, "One small step."
3. What is another name for the wishbone?
a
Furcula
b. Lucky bone
c. Shoulder blade
d. Sternum
4. Today, it's widely accepted that all of the two-legged meat-eating dinosaurs known as theropods-
Including T. rex and Albertosaurus-had at least very simple fuzzy
feathers covering their bodies.
According to the tree
you built, what distinguishes the feathers
of modern birds and Archaeopteryx
from the feathers of
other theropods?
a. Barbs
b.
Fibers
c. Filaments
d. Shafts
5. A clade is a fancy word for any group in a phylogenetic
tree that includes an ancestor
and all of its descendants.
A simplified dinosaur
tree is to the right.
Imagine that you have a pair of scissors and can cut the tree.
You can tell a
group is a clade because it would only take one
"snip" to make the
group "fall off" the tree. Five different clades
have been marked on the tree with brackets.
The clade marked 1 is clade Aves-the birds.
The clade marked 2 is clade Theropoda-the theropods.
Clades 2 and 3 are the two major groups of
dinosaurs-clade Saurischia and clade Ornithischia.
Finally, clade 5 is clade Dinosauria-the dinosaurs.
a. Mark on the tree using numbers 2-4 where you can "snip" off each clade. Numbers 1 and 5 have
been done for you.
b. Triceratops belongs to two of the marked clades on this tree: 4 and 5. This means that Triceratops
is both an
ornithischian (clade 4) and a dinosaur (clade 5). Which clades do birds belong to?
c. Use your answer to part b to explain why birds are dinosaurs.
NOVA PBS Learning Media WGBH
Biogen
Foundation
6