Look for: In Observations to Evaluate Claims, look for…

In Observations to Evaluate Claims, look for students’ connections between their observations and the evidence the class recorded on the evidence chart as evidence we would expect to see to support each claim. Look and listen for student evaluation of the different claims in light of their observations from the video and images. Students should be able to describe or reference their drawings or written explanations on Observations to Evaluate Claims to describe how cells grow and split to make more cells to fill the gap. The size and shape of the old and new cells should remain the same. (The actual type of cell used in the drawing or description is not important here.)

If students struggle with evaluating the different claims, remind them that we are trying to figure out what is happening at the injury site to fill the gap. Ask them to describe what they observed the cells doing in the video and differences they see in the microscopic images of the whitefish and onion root. If necessary, have students replay the video and help them connect how their observations involve old cells splitting and filling the gap with new cells. Then have them return to the images and claims on the How Does Skin Fill the Gap? poster to assess which claims best describe what we observed and which ones don’t. Have students explain their reasoning.

Bring the class together and facilitate a brief discussion using the prompts below.

Suggested prompt

Sample student response

What are some things you noticed in the video?

• There seemed to be way more cells at the end than at the beginning.
• All the cells looked the same, they had a similar shape and size.
• The cells that were produced looked the same as the original cell after the split.

In Lesson 8, we watched a zoomed-out view of skin healing. Using what we figured out from this first video, what could be happening in the gap where the skin was injured?

• Maybe it means that more cells are being made and that these new cells are filling the gap.
• After the split, these new cells just sort of pull together or clump up to close the gap.

Were all the new cells being made at the same time?

• No, each cell split at different times.
• We would see some light up and split apart at different times than others.

What are some of your ideas for why the new cells aren’t all made at the same time?

Maybe because different parts of our body need cells at different times … like the gap in the foot needed more cells to close up and heal, but parts of the skin that weren’t injured don’t need to be making all those cells.

So if we want to figure out more about what is happening when new cells are being made from original cells, what might help us see this process?

• I think we need to look closer up at what is happening when new cells are made.
• Yeah, I agree. The cells in the video were so small and everything happened so fast it was hard to see exactly what was happening.