Comparing Plants and Animals

According to cell theory, all living organisms are made of cells. Cells are the basic unit of structure and function of all living things. In this activity you will explore the similarities and differences between plant and animal cells.

Onion Cell

1. Prepare a wet mount slide of a small piece of onion skin. Add 1-2 drops of methylene blue or Lugol's iodine to the slide, then apply a coverslip.

2. Observe the cells and identify at least 3-4 cell structures.

3. Take a photo of the onion cell with the motic cam. Measure an average cell with the motic cam. Add a title, 3 labels, and a descriptive caption.

4. Add concentrated salt solution to the slide and observe changes. Take another photo with the motic cam and label at least 3 parts to show changes.
Add a title and a descriptive caption to describe changes.

Questions:
1. Describe the shape and arrangement of the onion cells.(2)

2. What happened to the cells when concentrated salt solution was added to the cells? (1) Why do you think this happened?(1)

3. What was the purpose of adding the methylene blue or Lugol's iodine to the slide?(1)

4. What question do you have about this activity that has not yet been answered?(1) Do research to answer the question or design and perform an experiment to answer the question.(2) Remember to cite your sources.

5. Explain what happens when salt water is added to an onion cell. You must use these words in your explanation: osmosis, diffusion, hypertonic, and hypotonic.


Elodea Cell

1. Prepare a wet mount slide of an elodea leaf. Remember to apply a cover slip. Move the slide around until you observe the elodea cells clearly. (Hint: Sometimes along the edge of the leaf the cells are more visible).
2. Observe and identify 2-3 structures.
3. Take a photo of an elodea cell with the motic cam. Measure an average cell with the motic cam. (Remember to measure the length, not the width).
Add at least 2 labels to the elodea cell.
4. Add concentrated salt solution to the slide and observe changes. Take another photo with the motic cam and label at least three structures to demonstrate changes that occurred.

Questions:
1. Compare and contrast the onion cell and the elodea cell.(2)

2. Did the elodea and the onion cells react similarly to the addition of salt water? Explain.(2)

3. What question do you still have about elodea or this lab activity?(1) Do research or design and perform an experiment to answer the question.(2)
Cite your sources.


Cheek Cell Lab

1. Obtain a flat toothpick and carefully scrape the inside of your cheeks. Add 1-2 drops of water to a slide, then add the cheek cells to the water by swirling the toothpick in the water. Add a drop of Lugol's iodine to the cell suspension. Carefully add a coverslip.
2. Observe the cells to identify 3-4 structures.
3. Take a photo of the cheek cell with the motic cam. Measure an average sized cell with the motic cam. Label at least 3 structures.
4. Finish by adding a title above your photo and a descriptive caption consisting of 1-2 sentences below the photo.


Questions:
1. Describe the shape and arrangement of the cheek cells.(2)

2. Compare and contrast the cheek, onion, and elodea cells.(6)

3. What question do you still have about this activity?(1) Do research to find the answer or design and perform an experiment to answer your question.(2)
Cite your research sources.

Assessment:

plant_and_animal_cells_checklist.png

Cell homework #3: How do the sizes of the onion, elodea and cheek cells compare to one another? Backup your statements with research with other sizes of cells (do not just restate the sizes, but create a comparison.) How do all the activities make a common statement about cells, parts, size...?
Need help with this question? Think about the following and answer: What do you notice that is different or similar between the different cells in lab (the parts that it contains, the sizes of the cells, etc.)? Research any other kind of cells that exist. What sizes are they? How does that compare to the sizes of the cells that are from the lab?

Does this help?
Cell homework #4: Discuss how size is estimated using a microscope manually in your own words.