Weigh a Dinosaur
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This page first made public: Jul 1, 2009
I also use a variety of this in an honors freshman dinosaurs seminar. In that class I make it more of a writing assignment—they have to provide a true laboratory "write-up" replete with "materials and methods" (what did the measure and how) and compare it to a published compendium of dinosaur body mass estimates, analyze their results, provide sources of error, and so on.
If time allows, it is useful to have students compare different models of the same dinosaur. It is relatively easy to acquire multiple version of common dinosaurs such as Triceratops, T. rex, Stegosaurus, and various sauropods.
Skills and concepts that students must have mastered
How the activity is situated in the course
Content/concepts goals for this activity
Importance of careful measurement
Higher order thinking skills goals for this activity
Develop an understanding that a lot of work can go into a simple observation such as "a tyrannosaur weighed 4-6 tons."
Other skills goals for this activity
Description of the activity/assignment
Students then determine how much water their model displaces. NOTE: Most textbooks show this happening with a beaker. Beakers are no where near accurate enough to use, and many dinosaurs dont fit in them anyway. You need either extremely large graduated cylinders (unlikely) or else large containers in a sink. What works best is to have students fill a container to overflowing (in the sink, obviously), then gently dunk their dinosaur, causing the vessel to overflow, then retrieve their dinosaur. THEN you can use a graduated cylinder to refill the container and measure the amount of water displaced.
Once students have a scale and a volume, the can cube the former and multiply it by the latter to yield an estimate of the volume of the actual dinosaur. Multiplying this by a density estimate provides an estimated mass. I have them bracket it by taking 0.9kg/L and 1.05kg/L for "light" and "heavy." Feathered theropods are even lighter---I have them use 0.8 g/L for the light estimate. They then record their result (I am trying to generate a spreadsheet of these measurements over the years) and compare it to a published estimate. I should probably base their grade on the ratio of their estimate to the "actual" (if light, reversed if heavy) but generally just try to "police" the work---if they are way off, they need to go back and find what arithmetic error led to the problem.
In the introductory classes this is a simple 1-sheet worksheet (front and back). For the honors students, they take the assignment home and write it up.
PS. I let the anthropology majors play with models of Pleistocene megafauna instead.
Determining whether students have met the goals
Download teaching materials and tips
- Activity Description/Assignment:
- Instructors Notes:
- Solution Set:
Lucas, S. G., 2004, Dinosaurs: The textbook: Boston, McGraw Hill, 280 p. (more recent versions available).
Martin, A. J., 2006, Introduction to the study of dinosaurs: Malden, Blackwell Publishing, 560 p.
Peczkis, J., 1994, Implications of body-mass estimates for dinosaurs: Journal of Vertebrate Paleontology, v. 14, no. 4, p. 520-533.