Labs 2 and 4 have been adapted from material presented by Dr. Robert Bakker at the 1993 NSTA convention . Lab 3 was developed in response to an article on the work of Dr. Neill Alexander which appeared in Discover magazine (October, 1990).
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Type of Activity:
Background Information:What question does this activity help students to answer?
This activity actually consists of a series of four separate laboratory investigations. These labs are intended to help students explore specific aspects of dinosaur biology, to develop reasoning/investigative skills, and to understand the relationships between animal anatomical form and function.
Notes for teachers:
1) The relationship of cranial volume to size of cerebrum and behavioral complexity
Required of students:
Preparation time needed:
Additional teacher preparation time may be needed to familiarize oneself with evolutionary biology and dinosaur paleontology. A general knowledge of dinosaurs is sufficient. You don't have to be a dino expert to get results from these labs.
Class time needed:
Abstract of ActivityThis activity is actually a series of four separate, but related, laboratory sessions dealing with the biology of dinosaurs. I use the labs in my vertebrate zoology class. They could be utilized in any biology class for the teaching of investigative lab skills and/or the studying of animal form and function.
Laboratory 1 investigates the relative cranial capacity of dinosaurs. In this lab, students must work in teams to devise a way to measure the relative cranial capacity of two simulated dinosaur skulls. Lab 2 involves a comparative study of the musculature and skeletal anatomy of both a dinosaur and a bird forelimb. This lab serves as a review/reinforcement of our previous discussion of homology. Lab 3 introduces students to the idea that we can determine information about extinct forms through experimentation. In this lab we use model dinosaurs to estimate the weights of the living forms. In Lab 4 we combine the techniques of measuring, calculating, and graphing in order to devise a system which will allow us to estimate the running speeds of dinosaurs.
1) Mammal skulls which serve as simulated dinosaur skulls for Lab 1. One opossum skull and one house cat (or raccoon) skull per student group. These can be obtained from commercial sources such as Carolina Biological Supply. Other sources may include local game officials or university science departments. Material such as sand, or table salt, and a graduated cylinder for measuring cranial volume should be available.
Laboratory 1 - Determining the Cranial Capacity of Dinosaur SkullsIn this lab we want to: 1) consider what information we might gather from the fossilized remains of dinosaurs and 2) create a situation in which the students must try to decide for themselves how to best collect this information.
More readily available mammal skulls are used to simulate dinosaur skulls and we pretend that we have found two new dinosaur fossils. One (simulated by an opossum skull) has a small cranial cavity. The other (simulated by a cat or raccoon skull) appears to have a much large brain case.
The student's job (working in pairs) is to deduce a way in which they can actually measure (in cubic centimeters) the size of each "dinosaur's" brain case. The teacher may offer suggestions as to the relative merits of the methods they have devised, or allow them to work independently. Most students first try to simply measure the outside dimensions of the skull as though it were a box. Others may use string to achieve more accuracy. The best method is to fill the skull with a material such as fine sand (interior passages may be plugged with small tufts of cotton) and then measure the sand by pouring it out into a graduated cylinder. If one allows for individuality, the different measuring techniques can be compared for accuracy at the end of the lab for evaluation purposes.
The lab may be extended by having a follow-up discussion on vertebrate brain regions and functions and what we might conclude about the relative behavioral complexity of the two "dinosaurs" based on cerebral size. In the lab, we usually pretend that our small-brained dino is a herbivore, such as Stegosaurus, while the large-brained specimen is a carnivore (remember theVelociraptor in "Jurassic Park"). We then pursue the question of why the habits of carnivores might necessitate a higher degree of intelligence (stalking, ambushing, cooperative pack-hunting behavior for example).
Laboratory 2 - Comparative Anatomy of Dinosaur and Bird ForelimbsPrior to this lab, students have been exposed to the principles of evolution and have an understanding of homologous organs and how they are used as evidence for evolution and determination of phylogenetic relationships.
In this lab, we examine the forelimbs of a dinosaur and a bird. Students are asked to evaluate the degree of similarity and comment on the relationship of the two groups.
First, we examine the front limb of Allosaurus. This is done by projecting a 2x2 transparency of a museum specimen onto the chalkboard. Students will reproduce this image onto their drawing paper. Using reference books, students must then label the individual bones comprising the Allosaurus forelimb. Other dinosaurs such as T. rex or other theropods could be used.
After becoming familiar with the dinosaur's anatomy, we proceed to the bird forelimb by using a chicken wing. Initially we locate, draw, and label the major muscle groups of the wing in order to identify the various motions these muscles impart to the limb. Next we remove the muscles so that the bones of the wing are exposed. These are also drawn, identified, and labeled.
The drawings are a necessity. Without them, students have a tendency to make only brief, superficial observations. Lab drawings focus their observations and attention to the detail which is an important part of accurate anatomical analysis.
This lab extends our previous discussion of evolution and homology and provides hands-on reinforcement of the concepts as well. Evaluation is done in two ways. First, the accuracy of the lab drawings is taken into account. Disparity in artistic ability is considered. The final evaluation, however, is based on an essay response by the students. In this essay, the students present their opinion of the debate over the relationship of dinosaurs and birds. Based upon what they have observed in the lab, they are instructed to consider such questions as: Are the forelimbs of dinosaurs and birds homologous? Is the anatomical structure of the two similar enough to warrant putting them into a class of their own - the Dinosauria? Students are asked to give specific anatomical evidence and use appropriate anatomical terminology within their essay.
This is a complex subject and potentially a sensitive one as well. Teachers must assess their student's ability to intellectually and philosophically consider these questions. This lab can lead to some highly interesting debate and interplay among students or it can be limited to a more basic study of functional anatomy.
Laboratory 3 - Estimating the Weight of Living DinosaursLab 3 offers the opportunity for students to develop measuring and calculating skills while learning that these can be applied to animals which are actually extinct and thus not available for direct observation.
During this lab students obtain volume estimates of dinosaurs by lowering accurate models into water and noting the volume which is displaced. For small models, one may use large graduated beakers for measuring. For larger models, a measuring chamber may be made by pouring known amounts of water into a plastic specimen bucket and marking the graduations with a water-proof laundry pen on the inside of the container.
Models (we use Brontosaurus, Tyrannosaurus, Parasaurolophus, and Stegosaurus) are lowered into the water by means of a string tied around the neck. The amount of water displaced is then recorded. Using reference books, we then find the length of the dinosaur. Next the length of the model is determined (both figures in inches). The relative size of the model is determined by dividing the length of the real dinosaur by the length of the model. This gives us a fractional size for the model which can then be plugged into a formula for determining mass.
For simplification we assume that a gram of living tissue (0.95 g) actually weighs the same as l cc of water (l g). The final mass calculations are made using the following formula:
This formula is adapted from Dolph, Dolph, and Dolph.1995 (Horsing Around. The Hoosier Science Teacher. Vol. 21(2): 56-59).
For assessment and evaluation purposes the students are asked to calculate the weights of the dinosaurs in kilograms (the figure derived by using the formula), pounds, and tons. This simply gives them some practice in metric-English conversion.
Laboratory 4 - Devising a System for Estimating the Running Speeds of DinosaursLaboratory 4 is intended to do two things. First, it relates animal form (limb structure) to animal function (running ability). Second, it gives students an opportunity to observe, measure, graph data, and predict outcomes from these data.
Students will need to be made aware that the ratio of the length of the lower leg and ankle to thigh length has been used as an index of running speed in animals (Bakker, 1986). As a general rule, the greater the lower leg to thigh ratio, the faster the animal can run. Using this as a premise, students devise a system for estimating dinosaur running speed based on leg measurements.
The lab begins by projecting 2x2 transparencies onto a screen at the front of the room. These are pictures of mammals of various running speed abilities. Students take turns going to the screen and measuring the lower leg/ankle length and thigh length of the mammals. These are recorded and they then divide the lower leg/ankle length by the thigh length to get ratio for comparative purposes.
Next, students look up the running speeds of these mammals in a reference (Bourliere's The Natural History of Mammals is a good source).
The next step is to plot the lower leg - thigh ratios of the mammals against their running speeds on graph paper. Onto this graph a line of best-fit is applied. Students now have a tool for predicting dinosaur running speeds. Given a series of dinosaurs, they should be able to measure their lower leg -thigh lengths, determine the ratios (reference books or teacher-supplied diagrams of dinosaur limbs are needed), and locate the ratio on the graph. By moving across to the line of best-fit, and then proceeding downward vertically to the running speed, the estimated speed of the dinosaur in question can be determined.
You may evaluate the lab by stopping at this point and seeing if the speed estimates the students derived were accurate based upon their graphic data. However, this is more an exercise in thinking. It is not without sources of error and offers opportunities for extension. Students will probably discover some apparent discrepancies in leg/speed ratios depending on what mammals you used in your initial measurements. They may point out (or you may make this part of the extension) that direct comparison of mammals and dinosaurs may not be valid. Are they anatomically alike? Metabolically alike? What about differences in range of limb motion and how it affects speed? How do joint angles affect speed? All these can be points for further discussion.