Viewing Plant & Animal Cells
Lesson 6 of 7
Objective: SWBAT prepare and observe cells from both a plant (onion) and animal (cheek).
Day #1 Making An Onion Skin Wet Mount Slide
"A video is worth a thousand words," refers to the notion that complex ideas can be conveyed in just a single image or a short, simple video. Try it with your students.
Before viewing the video:
I discuss that the process is broken down into a two day investigation. Day # 1 students will prepare and observe a plant (onion) cells and Day #2 students will prepare and observe animal (cheek) cells.
The video illustrates the steps to prepare a microscope slide and are a good visual for students that are unfamiliar with the equipment, tools, and vocabulary of this life science lesson. Important vocabulary words (Domain Specific Terms) for this lesson include: cell, organelle, nucleus, organism, microscope, and tissue. When working with new vocabulary:
I ask students to underline and/or highlight these terms as they read the instructions for the activity.
I post these terms on a word wall, interactive word wall or on the SMART Board or White Board.
After viewing the video:
To keep students accountable and guide my instruction, I use a formative assessment tool called an Admit Ticket. It is similar to an Exit Ticket but used at the start of the class period. The Admit Ticket contains the Sentence Frame "Now I know..." Sentence Frames are helpful in the writing process to ELL and Special Education students. I provide 2 minutes for students to write their Admit Ticket. Some answers I am looking for include:
- Now I know that in order to see cells of an onion you will need a very thin layer of skin.
- Now I know that in order to see an onion better you stain it with iodine.
- Now I know that the onion needs to be flat on the slide to see its cells better.
Then I ask students to verbally repeat the steps they have learned. Using popsicle sticks, I draw students into the discussion to review the important steps of this process.
Day #2 Cheek Cells Lab
Use the same process for viewing the video on Day #2
This lesson focuses on the DCI (Disciplinary Core Idea) LS 1. A. Structure and Function states that within cells, special structures are responsible for particular functions, and the cell membrane forms the boundary that controls what enters and leaves the cell. I ask students to make a connection between plant and animal cells and their special structures and particular functions.
The lesson also focuses on NGSS SP (#1) Ask Questions and Define Problems as I ask students to consider the questions "What do plant cells look like?" and "What do animal cells look like?"
The activity, categorized as Structured Inquiry, is inquiry guided by the teacher. I ask students to follow directions to come to a specific end point where they use a microscope to view and then draw, and label plant and animal cells. I also ask the class to write about and discuss the results when the inquiry is complete. I use analysis questions to guide the discussion such as "Predict what cell parts must be present but are too small to see with your microscope."
How did the cells differ?
Now, let's wrap it up. This provides opportunity to discuss what went right, what went wrong, and changes that could be made to the inquiry. This step is very important for students to "come full circle."
I have learned that you need to take students back to the question so they can think about the process. How did the cells differ? Take 1-2 minutes for students to process this question and wrap it up. Then, take 1-2 minutes to share answers with the class so students can hear other student thoughts. One important student response should be: The plant cell has walls and the animal cell doesn't.