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NOVA scienceNOW: T. Rex Blood?

Viewing Ideas

Before Watching

1. Play a game to help students understand the field of paleontology. To help students better understand what paleontology is and what paleontologists do, play a question-answer game. Ask the class the questions below. Should a question stump them, invite them to make an educated guess. If they are unable to answer the question, read the answer aloud. The answer to each question provides a clue for subsequent questions. So even if students lack the prior knowledge for answering a particular question, they can use answers from earlier questions to construct reasonable responses to later ones. Make sure they understand that this activity is meant to be a fun way to review terminology and concepts using a challenge that draws on good listening, quick thinking, and logic.

   • What is a fossil? (A fossil is any trace of a past life form. Fossils can be made of wood, bone, or shell. Soft tissues and tracks and trails can also be preserved as fossils.)

   • What is paleontology? (Paleontology is the study of fossils.)

   • How might an untrained person still make important contributions to paleontology? (Amateurs have made many important contributions to paleontology by finding and/or analyzing fossils.)

   • What personal characteristics might help a fossil hunter in his or her work? (Typical characteristics include: having an interest in fossils; being curious about the past; having the desire and ability to visit collecting sites; being attentive to detail; and possessing an analytic mind, a creative imagination, and a willingness to be persistent.)

   • What might a paleontologist be interested in learning about extinct organisms? (Paleontologists are interested in how organisms from the past functioned, behaved, and/or interacted. They also want to learn how characteristics of extinct organisms may relate to organisms alive today.)

   • Paleontology draws on many disciplines of study. How many can you name? (Biology, geology, ecology, anthropology, archaeology, climatology, and computer science)

   • Where do paleontologists conduct their work? (Paleontologists work both in the field collecting fossils and in the lab analyzing them.)

   • What kinds of technology would be useful in a paleontologist's work? (Paleontologists use imaging systems, modeling software, DNA-sequencers, and chemical-analysis tools.)

   • What can a paleontologist understand about the past by studying fossils? (Paleontologists develop understandings about how different types of organisms originated and died out since life first arose on Earth. They study fossils in an attempt to reconstruct our planet's history and to gain insight into life on Earth.)

2. Examine the anatomy of bones. The dinosaur skeletons and bones one typically sees on display—brownish fossils that preserve the bones' details—are fossilized through a process called replacement fossilization. In this type of fossilization, the living material is gradually replaced with minerals, such as iron or calcite. This turns the bone into rock. Paleontologists used to think that bones preserved this way always became solid rock. But when Mary Schweitzer and her team removed the minerals from the 68-million-year-old Tyrannosaurus rex femur, she discovered a soft, elastic bone material that contained evidence of possible blood vessels, red blood cells, and bone-forming cells.

   To have students understand that bone is more than just a solid, inert material like rock, ask them what kind of evidence could suggest that bone is a living tissue. (Bones heal when broken; they grow; we can feel pain and pressure in bones because they have nerves; they are supplied with blood; some bones produce material required by the body, such as red blood cells.) Next, bring in several beef bones for the class to observe. They are available as stew bones from the grocery store and come on Styrofoam trays wrapped in clear plastic. Ask the butcher to cut some in cross section along the long axis and others in cross section along the short axis. Refrigerate until class time. Keeping the packages closed, distribute them to student groups. Tell students that bone is made of minerals, mainly calcium and phosphorus, and contains living tissues, including blood vessels and cells that maintain and make new bone cells. Have students use a magnifying glass to note the different parts, tissues, and textures and identify where the blood vessels are located. (In the center) Ask students why blood vessels are important to the health of the bone. (They carry oxygen and nutrients to the cells; they carry away waste; and they transport materials produced inside some kinds of bones, such as the femur.) If appropriate for your class, consider having students extract DNA from the marrow inside the bones.

   As an extension, remove the hard mineral part from a set of bones: About a week before showing the segment to your class, soak chicken bones in vinegar. Because they are thin, wing bones and drumsticks work well. First, boil the bones and remove as much tissue as possible. Then, place the bones in containers of vinegar. Change the vinegar daily. On the day of the activity, bring in chicken bones that have been washed clean but not soaked in vinegar. Give students gloves to wear and have them feel the bones and note differences between the vinegar-soaked and the untreated bones. (The soaked bones are pliable. Vinegar dissolves away most of the calcium phosphate, leaving the stretchy material, elastin, and collagen protein fibers.) Tell students that the material that remains after soaking is similar to what Mary Schweitzer and her assistant found after they removed minerals from part of the dinosaur femur.

After Watching

1. Discuss how biological material typically decays. The recycling of nutrients is at the core of many important ecological cycles. In general, if life forms such as fungi and bacteria can make use of a material as a source of nutrients and energy, they will degrade that material over time. Since the "rotting" of organic materials is a natural process, have students list different ways we preserve our foods. Have them discuss just how these preservation methods slow or stop decay.

   • Vacuum packing or immersing food in oil excludes oxygen, thereby slowing or stopping growth of bacteria and fungus.

   • Sterilizing, boiling, and pickling kill most bacteria.

   • Refrigeration and freezing slow or stop growth of bacteria and fungus.

   • Drying, salting, or storing food in sugar-rich preserves and syrups creates a dehydrating environment, which slows or stops growth of bacteria and fungus.

   Identify which of these preservation methods is most like the one that preserved the Tyrannosaurus rex femur featured in the segment. (Vacuum packing and dehydration)

2. Develop a timeline showing when dinosaurs roamed and when humans arose. Many people mistakenly think that dinosaurs and humans coexisted. In fact, about 40 million years passed between the last dinosaur and the first hominid. It took another 25 million for modern humans to arise. Considered another way, if one were to measure Earth's age as a single 24-hour day, each minute would represent just over three million years. The golden age of dinosaurs would start a little before 11 pm and end around 11:39 pm. The first human civilizations would appear less than a second before midnight.

   To help students develop a better understanding of just how long ago dinosaurs lived and how long the soft tissue inside the Tyrannosaurus rex bones had to endure, have them sequence the appearance of different kinds of organisms in the fossil record. Before class, write out on a piece of paper the entries in the ten cells below that are listed in the column farthest to the right (i.e., Life Forms That Arose). Place them out of sequence on your paper so students cannot tell which came first, second, etc. Next, make enough photocopies of this sheet so that there is one sheet per three or four students. Then, on the board, copy the dates in the column labeled Years Ago. (If appropriate for your class, include the first three columns.) Give each group a sheet and ask them to match as best they can a set of organisms with a time period. Finally, as a class, discuss the correct pairings or provide students with a copy of the Table below. Emphasize the vast amount of time between when dinosaurs roamed Earth and the advent of humans. Point out that mammals appeared as early as the Triassic (248-213 mya) but that they only began to diversify after the dinosaurs disappeared. Discuss why paleontologists doubted the claim that Mary Schweitzer had recovered soft tissue from the Tyrannosaurus rex leg bone.

   
   

   The appearance of different life forms in the geologic record

   Era	Period	Epoch	Years Ago	Life Forms That Arose
   Mesozoic	Triassic		248-213 mya	First turtles, cycads, lizards, dinosaurs, and mammals
   	Jurassic		213-145 mya	First squids, frogs, birds, and salamanders
   	Cretaceous		145-65 mya	First flowering plants, snakes, and modern fish. Considered the heyday of the dinosaurs—the golden age of dinosaurs
   Cenozoic	Tertiary	Paleocene	65-55.5 mya	Major asteroid impact near the Yucatan peninsula. Diversification of mammals
   		Eocene	55.5-33.7 mya	First marine and large terrestrial animals, including horses, whales, monkeys
   		Oligocene	33.7-23.8 mya	First grasses, apes, and anthropoids
   		Miocene	23.8-5.3 mya	First hominids
   		Pliocene	5.3-1.8 mya	First Australopithecines
   	Quaternary	Pleistocene	1.8 mya-8,000 ya	Mammoths, mastodons, and Neanderthals
   		Holocene	8,000 ya-present	First modern human beings

   
   

3. Discuss the role technology plays in making new discoveries. Thanks to technology, paleontologists have an array of tools that let them see things in new ways. For example, imaging technology enables scientists to look at the minute features in a dinosaur skeleton, and modeling technology gives them insight into how dinosaurs moved. Point out that when technology reveals new information or provides a new perspective, the resulting insights can lead to new questions. Find out what new questions students were able to ask after they examined something under a microscope, such as onion cells. What did the technology (i.e., the microscope) reveal, and what questions could they now ask that were impossible to ask before they saw the onion skin in great detail? Make a list of questions raised by or mentioned in the segment that students think were inspired by technology-related insights.

4. Research how ancient swamps became arid deserts. Today, the places in Madagascar and Montana where the fossils mentioned in the segment were found are both arid. But when dinosaurs roamed, these regions were much wetter. The landscape changes in response to changes in climate. And climate can vary in response to such changes as the position of continents (i.e., plate tectonics), atmospheric composition (i.e., levels of carbon dioxide), the size of the polar cap (i.e., Earth's ability to reflect sunlight), and the intensity of sunlight (i.e., sunspot activity). The Tyrannosaurus rex and the Madagascar dinosaurs mentioned in the segment lived during the Cretaceous period, 145-65 million years ago. Ask teams to research how and why swamps could have eventually become deserts. What kinds of dinosaurs lived in what today is North America? What kinds of dinosaurs lived in your state or region? What was the climate in your area like during the Cenozoic? What kinds of fossilization would this climate have promoted?

Web Sites

NOVA scienceNOW
www.pbs.org/nova/sciencenow/3411/01.html
Offers T. rex-related resources, including a look inside dinosaur bones, streamed video, and an Ask the Expert" area where site visitors can questions to paleontologist Mary Schweitzer.

Anatomy of Living Bone
teachhealthk-12.uthscsa.edu/curriculum/bones/bone03-livingbone.htm
Includes a coloring sheet, lessons, and activities about bones.

NC State Paleontologist Discovers Soft Tissue in Dinosaur Bones
www.ncsu.edu/news/press_release/05_03/075.htm
Describes Dr. Mary Schweitzer's discovery of soft tissue in a fossilized dinosaur femur.>

SUE at the Field Museum
www.fieldmuseum.org/sue/kids.html
Presents SUE, the world's largest, best preserved Tyrannosaurus rex fossil.

Books

Eyewitness Fossil
by Paul Taylor. Dorling Kindersley, 2000.
Includes information about how fossils form and introduces different kinds of fossils.

T-Rex To Go: Build Your Own from Chicken Bones
by Chris McGowan (writer) and Julian Murdock (illustrator). Harper Perennial Books, 2006.
Provides instructions for building a chicken-sized model of Tyrannosaurus rex.