I begin this lesson by asking students to answer the following question:
"With so many organisms that die everyday, why is it that only a small percentage of organisms that ever lived actually become fossils?"
I have students brainstorm answers with their lab tables and record their thoughts in their science journal. The quality of answers depends on the background knowledge of students. At this time in my district Earth Science has been overlooked for a number of years. Because of this, the background knowledge of my students is pretty spotty. After giving students a few minutes to brainstorm, I provide them with How Fossilization Creates Fossils from cK-12 that discusses the reasons why fossilization is so rare.
After students read through the article, I have them share their responses to the question and follow up by showing this video (it is the one from the article) if students did not have access to the digital version of the reading.
This is another appropriate video that builds on how fossils are created.
At this point students will begin to discover how to analyze skeletal remains to make inferences about an organism. I start by discussing with students that there is a lot of information about an animal is lost during the fossilization process.
I use the PowerPoint interpreting Horse and Dino Skeleton to guide students through this idea. First I ask students to create a list of everything they know about horses. Next, I have students create a list of the parts of the body that would not fossilize, such as skin, hair and internal organs. While showing students a drawing of a horse skeleton, I ask, “What would we know if this animal was extinct?” Students should use their initial list of facts as a starting point. As they progress, they should begin to recognize that there is a lot of information on their list that cannot be derived from fossilized bones and teeth (SP4 Analyzing and Interpreting Data - Analyze and interpret data to provide evidence for phenomena).
Repeat this using the picture of the skeletal stegosaurus. At the end of this activity, have students respond to the following question in their science log: “There are a lot of illustrations of dinosaurs. Do you think that these drawings represent what these dinosaurs actually looked like? Why or why not?”
To provide the students with practice, I ask them to explain how they think scientists determine the external features of these fossil remains and give them an example for practice (it is part of the Interpreting Horse and Dino Skeleton PowerPoint. Students are instructed to create an illustration that depicts what the actual animal (with its outer layer) looks like. Once students have drawn their interpretation, I have them complete the Description/Justification Chart to provide more information and practice inferring and justification. I am looking for students to use what they learned in previous lessons about comparing the fossil to something that is alive today and using it as a source of reference to guess about the ecosystem and the look of the creature. I am looking for logic, not necessarily accuracy at this point. This video explains how I use these resources with my students.
The following video provides an example of students discussing the stegosaurus skeleton to determine what type of food it eats. I would like to point out that it does not matter if they already know the answer because the focus is on how they use the fossil image to justify their answer.
Here is a little more detailed description on what happened following the students' work on interpreting a fossil.
I then explain to students that all of this fossil evidence makes up the fossil record and how we use this record to help us understand long-extinct species and their connections to modern day animals. WiseGEEK has an easy to understand explanation of what the fossil record is and how scientists use it to gain understanding.
The following videos give some insight into how the fossil record works to give us information on extinct organisms. I have several sets of preserved spiders around my classroom so the spider video is something my students can relate to very well. If you don't have any preserved spiders in your classroom I strongly suggest you invest in some. The students are fascinated by them and cannot stop looking at them even though they are equally disgusted by their presence. It is quite entertaining to witness! The human skull video shows how we can follow the migration patterns of organisms. Both videos need to be discussed with students to ensure understanding.
To conclude this lesson I have students complete a 3-2-1 exit slip where they write: