Teacher Background

INTRODUCTION

Understanding how scientists learn from fossils is an important concept for students. Students will use fossils of a Stegosaurus (ancient animal skeleton) and a horse (living animal skeleton) through the observation of skeletal drawings. After completing this learning experience students will be able to evaluate the importance of fossils and their knowledge of past life.

EDUCATIONAL OBJECTIVE

The student will analyze and interpret fossil evidence for individual organisms using a drawing of a Stegosaurus skeleton and a modern horse skeleton. The student will then produce either a written report or poster about their findings.

MATERIALS

The materials needed for this lesson are:

• One drawing of a horse skeleton for each student. Horse Skeleton in pdf
• One drawing of a Stegosaurus skeleton for each student Stegosaurus Skeleton in pdf
• Each group of students will need markers, crayons, or map pencils
• Three sheets of plain white paper for each student

TEACHER BACKGROUND

Fossilization is a rare event. The chances of a given individual being preserved in the fossil record are very small. Some organisms, however, have better chances than others because of the composition of their skeletons or where they lived. This also applies to the various parts of organisms. For example, plants and vertebrates (animals with bones) are made up of different parts that can separate after death. The different parts can be transported by currents to different locations and be preserved separately. A fossil toe bone might be found at one place and a fossil rib at another location. We could assume that they are from different animals when, in fact, they came from the same one.

Much information is lost in the fossilization process. Think, for example, of a vertebrate (such as ourselves). Much of what we consider important about our own biology is in the soft tissues, such as skin, hair, and internal organs. These characteristics would usually be unknown in the fossil state, because most of the time only bones and teeth are preserved (there are exceptional cases where soft parts are preserved). Bones and teeth are preserved together. This exercise is designed to get students to think about the quality of information that comes from the fossil record.

Any vertebrate animal can be used for this lesson. My suggestion is that at least one of them be a skeleton of an ancient animal. The skeleton of a mouse that you find in an owl pellet would make a great hands on skeleton also.

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Vocabulary:
Fossilization - the process of changing into a fossil

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Procedure:

1. The teacher will begin this lesson by having a short class discussion on fossils and fossil formation.
2. The student will list facts about a living animal. The skeleton of a horse is used here, but there are many other possibilities (e.g., cow, dog, cat, sheep). The list of facts on the horse might include, but not be limited to: large size, fast runner, eats grass, has grinding teeth, has long hair for a mane and tail, whinnies, is intelligent, is sociable with other horses, makes a good pet.
3. The teacher will ask the students the question, what would we know if this animal was extinct? Refer to the diagram of the horse skeleton and point out an important generalization of fossilization: most of the time, only the hard parts (bones and teeth) are preserved as fossils. Go through the list and ask the class what we would know about the horse if horses were extinct and all we had were fossilized bones and teeth of horses. We would know that it was a large animal and could probably make some good guesses about its weight. We would know that it had grinding teeth and therefore could probably guess that it ate some sort of tough vegetation like grass. The hooves would not be preserved, but the shape of the foot bones would be a good indicator that it had hooves. The skeleton would also be useful to tell us that it was a fast runner. But no details of the hair or skin would be known. Everything about social behavior and vocalization would also have to be guesses.
4. The teacher will ask the question, what do we know about fossilized animals? Pass out the diagram of the fossil Stegosaurus.
5. The students will interpret the stegosaurus in light of what they do know. The student will list facts about stegosaurus. The students can use the list they made in discussing the living animals. What paleontologists know comes from studying the hard anatomy, in this case bones and teeth. Anything else is a guess, although in most cases it is possible to base the guess on sound biological principles.

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Assessment/Learning Product(s):

Students will draw a picture of a made-up creature with adaptations for a special way of life. Examples: a fast flier that eats leaves from the tops of trees; a burrowing animal that digs holes so fast no other animal can catch it. Describe how this animal is special and how it accomplishes what it does. Could paleontologists find out about this way of life from the fossil record?