Students finish sorting their fossils from yesterday. I leave the sorting procedure up to the individual students other than strongly suggesting that they put fragments that are too small to categories together in a ""further analysis" or "DNA analysis possibly needed" pile.
Students are eager to put a name to their fossils and call on background knowledge that doesn't always apply when they are working at categorizing. Additionally, I watch for erroneous assumptions.
For example, one student was calling small pieces "twigs". Her explanation was, "I think this is a twig because it looks like a little branch." I agreed that is what it resembled. Then I asked, "What evidence do you have that this was a twig?" I suggested that she use that language in her written description. "This fossil looks like it is a twig because it's cylindrical and very thin." As I confer with students I continually emphasize the difference a few words can make when writing for science. Stating that the fossil is a twig is incorrect. Describing it as resembling a twig and explaining why can be helpful.
An example of a student who was making assumptions based on insufficient evidence is the boy who thought that "sharks" must be very common because he uncovered five of them on his fossil dig. It was reasonable of him to assume that they must be relatively common, or I would not be able afford to buy and let the class dig them up, but it is incorrect to think that an abundance of fossils in one locations definitively means that the animal species or group was common. I continually remind them that fossils are like all other areas of science. Researchers must collect reliable data in large quantities before they are able to make conclusive statements.
To that end, students were able to draw some conclusions about animal abundance in the next part of the lesson because they noticed some commonalities between the fossils from the Pliocene matrix from North Carolina (about 1.5 million years old) and the Devonian fossils from Morocco.
Here are a few of students' beginning observations.
We worked together as a class to be more specific about how they described what they had discovered. Here are some additional student observations:
One student observed, "There are similar looking shells in both the matrix from the Plicoence and the sand from the Devonian. They look almost exactly the same. It might be the same species or family. Because it was the Pliocence and the Devonian we can hypothesize that it is a very successful animal group. Also, we see similar shells right now, on our beaches."
Another student said, "I think I found a shark tooth in both the Devonian sand and the Pliocene matrix. I think that maybe they were successful because other animals they lived many years ago, (4.5 million), a long time ago (1 million), and if they are sharks, we still have some now."
An example of a student who made very specific comparisons said, "I found a fossil that is 1 millimeter big. My friend found a similar one that is 3 millimeters big. I noticed that the shell (I don’t know what it’s called yet) is circling like the Fibonacci sequence. The animal that lived in this shell is smaller than the shell. What even lived in it? What would something that small eat?"
In this piece of student work, the student demonstrates strong proficiency in both writing structure and content knowledge. He has a clear, descriptive topic sentence and specific details in the body of the paragraph that demonstrate high engagement with and understanding of the idea that fossils can provide information about the past.