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NOVA scienceNOW: T. rex

Viewing Ideas

Before Watching

  1. Compare Tyrannosaurus rex's weight with the weights of familiar objects. At maturity, Tyrannosaurus rex (T. rex) weighed about 12,000 pounds. To give students a feel for this large weight, have them compare T. rex's weight to familiar objects, such as a 2,000-pound compact car or a 100-pound student. For example, one T. rex equals six compact cars or 120 hundred-pound students. As an extension, assign teams one or more of the following animals—blue whale (largest on record is 390,000 pounds), elephant (12,000 pounds), hippopotamus (7,500 pounds*), white rhinoceros (4,000 pounds*), giraffe (2,500 pounds*), great white shark (4,500 pounds*), ox (1,400 pounds*), Clydesdale horse (1,700 pounds*), and cow (1,300 pounds*). Have them compare T. rex's weight with the weight of their animal (e.g., one T. rex equals three white rhinoceroses, which is a one to three (1:3) ratio). Have teams share their ratios in a discussion or by creating a poster. Visit NOVA scienceNOW's Growing Up T. rex to have students interpret a graph comparing T. rex's body mass to its age. Ask why it is impossible for a land animal to grow to the size of a blue whale. (On land, an animal's skeleton must support its full body weight. As weight increases, bone mass increases exponentially. Beyond a certain weight, the bones become so massive that the body functions poorly. In contrast, water's buoyant force helps support the bodies of many aquatic animals, such as whales. Thus, some aquatic animals grow to large size without greatly straining their skeletons.)

    * Approximate weight for an adult male.

  2. Illustrate what Earth looked like when T. rex was alive. Dinosaurs lived during the Mesozoic era, which lasted 160 million years. They inhabited every continent and a wide variety of environments. Have student teams draw pictures illustrating what North America's climate and surface were like during the three different periods of the Mesozoic Era—the Triassic (225-190 million years ago), Jurassic (190-136 million years ago), and Cretaceous (136-65 million years ago). Have them research when T. rex lived. (During the Cretaceous period) As an extension, ask teams to research the kinds of dinosaurs that lived in what today is the United States. What kinds of dinosaurs lived in their state or region? Have teams share their findings and make a time line showing when each kind of dinosaur lived.

After Watching

  1. Calculate how much weight T. rex gained per day during its growth spurt. A full-grown T. rex weighed about 12,000 pounds and stood about 15 feet high, making it one of the largest creatures in Earth's history. To reach this size, T. rex gained about 10,000 pounds from its 14th to its 18th year. Ask students to calculate the weight T. rex gained (on average) per day during this tremendous five-year growth spurt. (About 5.5 pounds)

  2. Determine an organism's age by counting annual growth rings. Paleontologist Dr. Greg Erickson found that he could determine the age of T. rex by counting the growth rings in its rib bones. Many plants and animals have markings that show annual growth, such as trees (rings), turtles (lines on the plates of the shell), mollusks (lines on the shells), and fish (lines on scales and the otolith bone). By counting the rings or lines, one can estimate the age of the animals. Have students visit the sites listed in the Resource section to find images of growth-related markings and determine annual growth in these organisms by counting the markings.

  3. Articulate questions inspired by the T. rex segment. Scientist Dr. Peter Mackovicky stated that insight into a process or phenomenon leads to new questions. For example, a better understanding of T. rex's growth and life span has raised a new set of questions about dinosaur size, growth patterns, life span, and relation to modern birds. Ask students to think of some questions related to the segment. Make a list on the board. Which ones would students be interested in investigating?

  4. Consider the role technology plays in making new discoveries. Thanks to technology, paleontologists—people who study dinosaurs and fossils of other plants and animals—have an array of tools that let them see things in new ways. Using advanced technology enables scientists to look at the minute features in a dinosaur skeleton, understand what dinosaurs ate, and model how dinosaurs moved. Point out that when technology allows people to see things from a fresh perspective, the resulting information can lead to new questions. Ask what new questions students were able to ask after they examined something under a microscope, such as onion cells. What did they learn by using the technology (i.e., the microscope), and what questions could they now ask that were impossible to ask before seeing the onion skin in great detail? What kinds of questions mentioned in the segment do students think were inspired by technology-related insights? Invite a parent or guest who works in the field of medical technology to share his or her work and be part of this discussion.

Links and Books

Web Sites

Clams & Mussels

Includes photographs and descriptions of many bivalves.

Davidson College Box Turtle Study

Includes close-up photographs of growth rings on turtle shells.

Introduction to Aging Fish: What Are Otoliths?
Describes otoliths in fish and shows how they are used to determine age of fish.

Missouri's Two Box Turtles
Shows how to use growth rings to determine the age of a box turtle.

Razor Clam
Provides information on razor clams, including determining age using growth rings.

Researcher Gives First-ever CAT Scans to Dinosaur Skulls
Describes how CAT scans are used to provide data on dinosaur skulls.

Ultimate Tree-Ring Pages!
Provides photographs of tree rings from several different kinds of trees.

Where did dinosaurs live?
Displays the earth during the Triassic, Jurassic, and Cretaceous Periods.


Hamilton, Jill, editor. Eyewitness Visual Dictionary: Prehistoric Life. New York: Dorling Kindersley, 1995.
Includes a geologic time line of Earth's history and information on T. rex and other dinosaurs.

Page, Martin, editor. Eyewitness Visual Dictionary: Animals. New York: Dorling Kindersley, 1991.
Includes information on the size and weight of large animals and on animal classification.

Teacher's Guide
NOVA scienceNOW: T. rex

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