Lab 2:  Cells

 

Together with your lab partner, you will be examining plant cells and animal cells using a compound light microscope.  The following outline is designed to take you through the steps of the scientific method, and proper lab procedures.  This is a formal assignment and will be collected.

 

 

Purpose:  ______________________________________________________

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Hypothesis: ____________________________________________________

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Materials: _________________                                  _________________

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Method:

1. Preparing a Wet Mount of  Onion Cells

 

1. Obtain (get) a small section (2 cm²)  of onion from the teacher
2. Using tweezers, remove a single layer from the inner side of the section of onion.  If the layer is not transparent try again. (It’s like peeling the backing off of a sticker)
3. Using tweezers, place the onion skin in the centre of a microscope slide.
4. Place two drops of water on the onion skin.
5. Cover it the skin with the slide cover.
6. Remove any air bubbles by gently tapping the slide with the eraser at the end of your pencil.
7. Examine the slide.  Note your observations.
8. Leave the cover slip down and place 1 drop of iodine at one edge of the cover slip.
9. Touch the opposite corner of the cover slip with a piece of paper towel.  (This will draw the stain across the slide under the cover slip.)

10.Examine the slide again.  Record your observations.

 

Choose a grouping of 4 cells.  In the space below, sketch the cells you see.  Label any structures you recognize (cell wall, nucleus, chloroplast, etc).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2. Making a Wet Mount of Human Cells

 

1. Using a popsicle stick, have one group member GENTLY scrape inside their mouth along their cheek.
2. Wipe the end of the popsicle stick into the centre of a clean slide.
3. Place two drops of water on the slide.
4. Cover it with the slide cover.
5. Remove any air bubbles by gently tapping the slide with the eraser at the end of your pencil.
6. Examine the slide.  Note your observations.
7. Leave the cover slip down and place 1 drop of iodine at one edge of the cover slip.
8. Touch the opposite corner of the cover slip with a piece of paper towel.  (This will draw the stain across the slide under the cover slip.)

10.Examine the slide again.  Record your observations.

 

Choose a grouping of 4 cells.  In the space below, sketch the cells you see.  Label any structures you recognize.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Conclusions:  (How are the two cell types different?)

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Application Questions:

           

 

1) Explain why the cells of the onion bulb do not appear to have any chloroplasts.  (Hint: Why would the function (job) of the bulb’s cells not need chloroplasts?)

 

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               Lab Write-Up Criteria                                       Level

All components of the scientific method have been completed and scientific terminology has been used.	1         2         3         4
Observations are accurate, complete and detailed.	1         2         3         4
Conclusions have been made based on the purpose and hypothesis stated in the lab.	1         2         3         4
Application questions are correct, show insight and demonstrate knowledge of cell structures.  Connections have been made.	1         2         3         4
Overall neatness – writing, diagrams and organization.	1         2         3         4

                                                                                   

     Overall Level: