David Alcazar
Daniel Lazo
Maria Villagomez
July 28, 2011
Science Topic and Research
Bone Structure in Modern and Prehistoric Animals
During the two and a half weeks, we investigated why prehistoric and modern animal
structures were engineered a certain way. We answered three specific questions for three
animals. While investigating, we looked at fossils with Mark Goodwin and looked at bones such
as mammoth femurs and triceratops horns. Then, we visited The Lawrence Hall of Science
which encases a dinosaur exhibit. We also figured out how a TEM works and what we can see
with it. From all of this we discovered some ideas and facts about why a certain animal like a
mammoth, giraffe, and triceratops is shaped a certain way.
For our final report of Topics in Science Research, we each chose individual questions
having to do with different bones in the body in different species. We covered several new topics
such as looking through a Transmitting Electron Micrscope (TEM) microscope, how an animal
handles its weight without having its bone buckle, and how to apply the aspect ratio to real
modern day animals such as the giraffe. Daniel has always been very interested in dinosaurs so
he decided to research dinosaurs that had intriguing bone structure, specifically horns. Daniel
knew that Triceratops had interesting horns because they would change angle when going
through different stages of maturity. Daniel wanted to know why the bones would move in the
way that they did so his question was: Why do Triceratops' horns curve into 3 different stages
during their lives, and is there any reason for them to change angle? David had always been
interested in animals during the ice age and how they adapted to their environment. Therefore
David chose to look at the Woolly Mammoth. David wanted to know how the bones of a Woolly
Mammoth could sustain its massive weight. David's question is: Do the bones of a Woolly
Mammoth mineralize at the same rate as it's body grows. Maria wanted to research a modern
animal so she chose to look at the giraffe. Maria's question was: How do the legs of a giraffe
support the weight and the high speeds they can reach.
For David's question he had to look at the composition of a Woolly Mammoth bone.
The main factor that I focused on was how Mammoths were capable of keeping their body's up
without their bones buckling. I researched and found that Mammoths must make their bones
extremely stiff and strong so that they can hold their exponentially growing body. One action
that takes place in the Mammoth bone is the disappearance of the marrow cavity. Since the
marrow cavity is hollow and makes the bone less dense, the Mammoth will mineralize the cavity
and make it solid. This will make the overall bone much stronger. Not only will it make the bone
stronger and more dense, the bone will grow 2x faster than before since Mammoth bones are also
very low when it comes to their aspect ratio. Aspect ratio is the ratio from the length to the width
of the bone. If that ratio is low then it indicates that strength was extremely important when it
came to holding up the massive weight of the animal. When changes in the bone take place the
crystals also reorient making them better for holding more weight. With the reorientation of the
bone, the osteons act like pressure filled tubes that make the bone stiffer increasing the capability
for the mammoth to hold its own weight.
To focus on David's question on whether the bones of mammoth mineralize at the
same rate as it grows, he needed dimensions for a large bone that sustained a lot of pressure. An
article on Mammoths was found that had the dimensions of a Woolly Mammoth Humerus. With
this information he could fine the standing compression stress on the bone. David was interested
in math so he decided to calculate it on his own. The formula for stress is: force(newtons)/area.
Finding the cross sectional area was simple because the width, or diameter, of the bone was
already provided. To find the cross sectional area you apply the formula of Pi*(r)^2. The width
is 28.3 cm so the radius would be 14.15. When you square 14.15 you get 200.2225 cm. When
multiplied by 3.14 (Pi) you end up with 628.69865 cm^2 or 6.286965 m^2 as your cross
sectional area. To find the force in Newtons you need to find the mass which is the weight in
kg*acceleration due to gravity (9.8 meters per second). Woolly Mammoths can grow to weigh
up to 16,000 pounds. This translates to 7257.477 kg. Multiply the weight by 9.8 m^2 and you get
71123.284. Then you divide 71123.284 (force in Newtons) by 6.286965 (cross sectional area),
and you get 11312 N/m^2. Do the same with the juvenile Humerus, but this time use the
dimensions of 31.5 cm in length and 14.6 cm in width. After doing the same calculations as
above you end up with the overall standing compression stress of 292.272 N/m^2.
To answer David's question he needed to see how much the elephant's weight
increased compared to how much the stress increased from childhood to maturity. The weight of
a juvenile Woolly Mammoth is about 110 pounds. While the weight of an adult Woolly
Mammoth is 16,000 pounds. The percentage increase in weight is 14545.45% from a juvenile
Mammoth to and adult. When comparing the stress, which is 11312 N/m^2 and 292.272 N/m^2,
the percentage increase is 3870.37%. These two percentages do not correlate with each other at
all showing that the Humerus must have changed while becoming an adult. The bone became
more stiff by mineralizing the marrow cavity which makes the Humerus much thicker and
stronger. This would relieve stress on the bone helping the Mammoth carry its massive weight.
The question Maria had was, How do the legs of a giraffe support their weight and high
speeds? and that made Maria realize how nature is an engineer. Since giraffes are not as ancient
they were not as explained where there was fossils of triceratops and mammoths. As Maria read
articles and listened in class Maria learned that a giraffe can run with its whole weight without
buckling. Giraffes are sprinters, slender, and quick. They do not run fast distances. She also
learned that a giraffes speed is about 32 mph and that a weight of a adult giraffe is approximately
3000 pounds while a baby giraffe weighs about 110 pounds Their bones have a lot of density.
Maria got to compare a Giraffe to a African buffalo. While comparing both of the animals Maria
found out that giraffes have higher mineral density and wider in cross mid section than a
buffalo’s. Its high aspect ratio is susceptible to buckling and bending. That is how it does not
break when it runs really fast with all the weight.
Having an interest for dinosaur since a child, Daniel choice a question on recent studies
of the three-horned lizard, Triceratops. After watching a television marathon on dinosaurs
before SMASH started, he wanted to know how and why were Triceratops’ horns changed
shape as it grew older and bigger. Before starting his study, Daniel thought the horns of the
Triceratops were used for fighting others of its kind during mating season, like deers and other
modern horned animals. He also thought the horns were made of keratin, the material that forms
a person’s hair and nails. When we visited the UC Museum of Paleontology, we were able
to tour with Mark Goodwin, an esteemed paleontologist that is currently studying the fossils
of triceratops and pachycephalosaur. His current research hypothesized that triceratops was
unlikely to use its horns for battle.
Having an interest for dinosaur since a child, Daniel choice a question on recent studies
of the three-horned lizard, Triceratops. After watching a television marathon on dinosaurs
before SMASH started, he wanted to know how and why were Triceratops’ horns changed
shape as it grew older and bigger. Before starting his study, Daniel thought the horns of the
Triceratops were used for fighting others of its kind during mating season, like deers and other
modern horned animals. He also thought the horns were made of keratin, the material that forms
a person’s hair and nails. When we visited the UC Museum of Paleontology, we were able to
tour with Mark Goodwin, an esteemed paleontologist that is currently studying the fossils of
triceratops and pachycephalosaur.
His current research hypothesized that triceratops was unlikely to use its horns for battle.
The horn would likely break if pressure is applied because one-third of the horn is hollow,
meaning filled with soft tissue or marrow. Using horns for defense and mating is mostly used
by mammals, such as deer and rams. Since dinosaurs are more genetically related to birds than
reptiles or mammals, the horn would have been used for distinguishing age and gender, like
for the hornbill and cassowary. The hornbill and cassowary have horn-like structures, called
casque, fused to their skull that change shape as it grows. As a juvenile, the triceratops' horns are
diminutive and straight. When growing into as a subadult, the horns start to curve backwards, but
the horns curve forward when a full grown adult. The change in horn orientation is tremendously
uncommon in most horns because triceratops horns are not actually a horn. The horns are
protrusions of epiparietal skull bone, or extensions fused to the the skull.
Though most bone is made of keratin, the triceratops horn is made of metaplastic bone.
Metaplastic bone rapidly grows while minimizing weight since it is used as an “ornament”
rather than a functional bone. The osteoblasts, cells responsible for bone formation, are absent
within metaplastic bone. In place of the osteoblasts are fibroblasts, cells critical for healing,
or remodeling, wounds. Cause of the change in cell types, the bone remains immature and
porous, never hardening into solid bone when close to adulthood. Having a close relation with
triceratops, the cassowary shares the characteristic of bone immaturity in its casque, being only
80% full grown when an adult. Metaplastic bone gave triceratops visual communication of age
and gender without giving extra weight to its enormous cranium.
Visiting Mark Goodwin and individually researching about the triceratops, Daniel better
understood the reason for a triceratops to have its so-called “horns.” Without the evidence of a
triceratops currently alive, Daniel concluded that the triceratops had transforming horns to have
visible identification of age and gender amongst its species. He also found out that metaplastic
bone was the material that caused the triceratops' horns to reorient. Overall, current research
could solve the true mystery of why and how a triceratops' horn reorientates.
Overall, this project has opened our eyes of what is actually underneath our skin, bones.
We have been studying this natural material for five weeks by using different microscopes,
reading science articles, and talking to well-known scientists. For David, he realized that woolly
mammoth bones adapt to the mammoth’s physical needs, such as weight of its body and hair. In
Maria’s research, she learned that giraffes’ leg bones are built to maintain high speeds, even with
its weight of 3,000 pounds. Daniel discovered that the triceratops’ horns are not made for
fighting as portrayed in children’s movies, but are actually made for visual communication to
determine its age and gender. Thanks to our mentor Elizabeth Boatman, we understand the
aspects and characteristics of bones.