Students will understand what can be learned from fossils and in doing so, realize the difference between fact and theory (idea). They will also gain a general understanding of how fossils are formed.
This lesson is the first of a two-part series on fossils. Many children today can name a dinosaur on sight regardless of how lengthy the name. Students are extremely interested in the topic. These lessons will go beyond naming dinosaurs and give students a broad understanding of how we know about the great beasts. They will start to acquire knowledge of the fossil record in preparation for learning about evolution and natural selection–concepts they will study in high school.
Fossils 1: Fossils and Dinosaurs focuses on what we have learned and can learn from fossils. In the first part of the lesson, students will discuss what we know about horses. They will then do the same for a Stegosaurus. This comparison is subtle, but demonstrates what we know as fact and what we know as theory, and more importantly, what sort of proof scientists need for fact to exist. As students discuss the Stegosaurus, they will realize that fossils tell a story about the animal. They describe facts, i.e. how tall, how wide, what kind of teeth, and they describe ideas, i.e. what the dino may have eaten, how fast it may have moved due to its leg structure, and how it may have hunted. Once students have an understanding of how to extrapolate facts and ideas from fossils, they will do some of their own digging in the second part of this lesson to practice using the thinking skills they've obtained.
Another part of the lesson briefly covers how fossils are formed. This is general information and does not get into the specifics of mineralization. The purpose is to identify the conditions necessary for fossilization. They have gone over this information in the first part of the lesson, however this exercise allows them to construct their own "story board" imagining the circumstances for another animal to become fossilized. Students also learn that it is rare for a whole skeleton to be fossilized–more often, fossil diggers find bits and pieces.
Fossils 2: Uncovering the Facts explores what information can be discerned by comparing fossils to living organisms.
Print out the directions from Activity 1: Fossilization for youself. You may want to get an overhead projector to show the picture of the horse (part of the Fossilization activity) to the class as you discuss what is known about horses. Each student will need a copy of the picture of the Stegosaurus (part of the Fossilization activity).
Sue, the T. Rex on display at The Field Museum, is perhaps the most famous dinosaur fossil of our time. Your students may already know about Sue, and even if they do, this motivation exercise will get students excited about the lesson to come. Students should use their Fossils and Dinosaurs student esheet to go to All About Sue. Tell students to read through each of the tabs: Sue's Significance, Sues's Vital Stats, Sue's Senses, and Sue's World. They can record their answers to these questions on the Fossils and Dinosaurs student sheet:
- What do we know about Sue?
(This information will include statistics, like how big the skull is, how many bones there are, where it was found, etc. List all of these things on the board.)
- How do we know all of these things?
(Students will likely answer bones or fossils. If not, the unanswered question foreshadows the lesson to come.)
- What is the significance of finding Sue?
(It is the most complete T. Rex skeleton ever.)
- How do we know this?
(Students should know that this is apparent through prior knowledge of other fossils and a comparison of Sue to other T. Rex fossils.)
The following questions will help you gauge what students know about fossils in general before starting the lesson.
- What's a fossil?
(Many students will answer bones, which is fine, but ask them if things like dinosaur eggs, or even nests are considered fossils. Trace fossils include eggs, nests, tracks, coprolites, and impressions.)
- How do fossils form?
(Though students may be very familiar with dinosaurs, they may not know the process that preserves the bones. If students cannot answer the question, that's O.K. They will learn this in the lesson.)
- What can fossils tell us?
(Here, you can lead the students. Remind them of all the things we know about Sue.)
To get students thinking about the quality of information that comes from the fossil record, go to Fossilization and Adaptation: Activities in Paleontology and do Activity 1: Fossilization, from Berkeley's Museum of Paleontology. Print out the directions for yourself. You may want to get an overhead projector to show the picture of the horse to the class as you discuss what is known about horses. Each student will need a copy of the picture of the Stegosaurus (pictures of the horse and the Stegosaurus are online as part of the activity).
Here is a summary of the lesson:
- You will list facts about the horse and other living animals. List things on the board, such as: large size, fast runner, eats grass, has grinding teeth, has long hair for a mane and tail, whinnies, etc.
- Ask, "What would we know about this animal if it were extinct?" Discuss that only the hard parts (bones and teeth) are preserved as fossils. So, ask students to choose those things listed on the board that indicate what we would know about the horse if all we had were fossilized bones and teeth. Circle appropriate things on the board that are listed, then make a list of "guesses."
- Ask students, "What do we know about fossilized animals?" Pass out pictures of the stegosaurus and tell students to interpret it, with both facts and guesses.
- Have the class put muscles and skin on the dinosaur. Discuss how imagination comes into the interpretation of fossils.
You will have discussed fossilization with your students when doing the activity. Now, reemphasize the discussions and the activity. On the board, make two columns. Title one, "What we know about dinosaurs." The other should be titled, "What we have to guess."
Then pose these questions:
- How do we know what we know about dinos?
(Review what was just discussed about horses and the stegosaurus: that bones can tell the size of the animal, possibly if it was a fast runner, what kind of teeth it had. List these things in the appropriate column.)
- What are things that we have to guess about?
(While fossils may tell exactly what kind of teeth an animal has, we have to guess about what it might have eaten. Also bring up students' colorings of the stegosaurus. Point out that we have to guess about the color of dinosaurs because fossils do not tell us what color they were.)
Here are some more questions to lead students into expanding on the list:
- How do you think the dinosaurs acted?
(And how could we know about those things?)
- How did they treat their young?
(Fossil evidence of nests would give clues. Some paleontologists have found crushed eggs and the skeletons of baby dinos in a nest. They think this suggests that the babies hung out in the nest long enough to crush all the eggs, and maybe dinos cared for their young. Other nests show eggs that aren't crushed, perhaps suggesting that the babies left right away.)
- Did they lay eggs or give live birth?
(Fossil evidence of eggs would put this in the "know" column.)
- Could the dinos see well?
(Fossil evidence of the skull would give clues, but would we know for sure?)
- How did dinos communicate?
How do fossils form?
Now that students understand what can fossilize, ask them how it fossilizes. Students should use their esheet to visit Fossils from BrainPOP Jr. to learn more about how fossils are formed.
Discuss the main points of the process:
- An animal must get buried fairly quickly.
- Why must it be buried quickly? (If it doesn't it would get eaten by scavengers.)
- How might it be buried? (It could be buried by volcano or mudslide.)
- Water helps bury the animal in sediment. (The burial process is crucial. It is also why many animals do NOT get fossilized. Discuss the probability of these circumstances being just right.)
- Soft parts decay.
- Sediment presses down and sand hardens to rock forming a fossil.
Have students draw their own diagrams demonstrating the process of fossilization with whatever animal they like. They should describe these three things. Remind them that the water could sweep over an animal and bury it in a flash flood or severe storm. Also remind them that whole skeletons rarely form because things get carried away. They are not limited to three boxes.
Have students use their esheet explore these two sites before the final assignment:
- Fighting Dinos, from the American Museum of Natural History's Ology website, uses fossil evidence to tell the story of a deadly clash between two dinosaurs.
- Science of Sue, from The Field Museum site, describes what researchers have learned from studying Sue - the largest, most complete, and best preserved Tyrannosaurus rex ever discovered.
After students have explored these sites, tell them to pretend they are in the shoes of a paleontologist (a person who studies dinosaur fossils). Students can use their Junior Paleontologist student sheet to:
- Pretend they work in a museum and they have just finished piecing together a nearly complete dino.
- Describe the dinosaur, and tell a story about its life, based on the fossil find.
- Use what we know about living animals to come up with ideas about the dinosaurs.
- Back their ideas by what they have found in the fossils. (If it's a meat-eater, describe its teeth.)
- Be creative… some scientists can get really creative when describing how the dinosaurs lived. Remind them to use phrases like: "this dinosaur might have," or "the fossil evidence suggests."
Follow this lesson with the next one in the Fossils series: Fossils 2: Uncovering the Facts, in which students continue to explore what facts can be determined by studying fossils, while focusing on comparing the remains to living organisms.