Download Comparing Animal and Plant Cells

Back
Lesson
Print
Name
Class
Date
Exploration Lab
Comparing Animal and Plant Cells
OBJECTIVES
Examine the similarities and differences between the structure of cells in
animals and the structure of cells in plants.
PROCESS SKILLS
• hypothesizing
• classifying
• observing
MATERIALS
•
•
•
•
•
• dropper bottle of Lugol’s iodine
lab apron
solution
safety goggles
• prepared slides of human epithelial
compound light microscope
cells
forceps
• sprigs of Elodea
• prepared slides of three unknowns
microscope slides and coverslips
Background
1. In this investigation, you will use a compound light microscope to observe
cells from animals and plants. First, you will view a prepared slide of human
epithelial cells taken from the skin lining the mouth. Then, you will make your
own slide of a leaf from Elodea, a pond weed.
2. Based on your observations of human epithelial cells and Elodea leaf cells, you
will be asked to classify three slides of unknown cells as either animal or plant
cells.
3. Before you examine any cells, list the structural characteristics that distinguish animal cells from plant cells.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Modern Biology
25
Datasheets for In-Text Labs
Back
Lesson
Print
Name
Class
Date
Comparing Animal and Plant Cells continued
PART A: ANIMAL CELLS
1.
CAUTION Handle glass microscope slides carefully. Dispose of
broken glass separately in a container designated by your teacher.
2.
CAUTION Do not use electrical equipment with wet hands or
near water.
3. Examine a prepared slide of epithelial cells under low power. Locate cells
that are separate from each other, and place them in the center of the field of
view. Examine the cells under high power. Adjust the diaphragm to reduce the
light intensity and achieve greater clarity.
4. In the space below, make a drawing of two or three cells as they appear under
high power. Identify and label the plasma membrane, the cytoplasm, the
nuclear envelope, and the nucleus of one of the cells in your drawing.
PART B: PLANT CELLS
5. Carefully tear off a small leaf near the top of an Elodea sprig. Using forceps, place
the whole leaf in a drop of water on a slide. Place a coverslip on top of the leaf.
6. Observe the leaf under low power. The outermost part of the cell is the cell
wall. The many small, green organelles in the cells are chloroplasts.
7. Locate a cell that you can see clearly, and move the slide so that the cell is in
the center of the field of view. Examine this cell under high power, and use
the fine adjustment to bring the cell into focus.
8. Find an Elodea cell that is large enough to allow you to see the cell wall and
the chloroplasts clearly. Make a drawing of this cell in the space below. Label
the cell wall and at least one chloroplast in your drawing.
9. The chloroplasts may be moving in some of the cells. If you observe no movement, warm the slide in your hand or shine a bright lamp on it for a minute or
two. Then, reexamine the slide under high power, and look for the movement
of the cell’s contents. This movement is called cytoplasmic streaming.
10. Because the cell membrane is pressed against the cell wall, you may not see
it. Also, the abundance of chloroplasts may hide other organelles in the cells.
You can make the cell membrane, vacuole, nucleus, and nucleolus more
visible by making a stained wet-mount slide of Elodea.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Modern Biology
26
Datasheets for In-Text Labs
Back
Lesson
Print
Name
Class
Date
Comparing Animal and Plant Cells continued
11.
Put on a lab apron and safety goggles. Prepare a wet-mount slide
of Elodea as you did in step 4, but substitute Lugol’s iodine
solution for the water. Allow the iodine solution to diffuse throughout the leaf.
12. Observe the stained cells under low and high power. Make a drawing of
a stained Elodea in the space below. Label the central vacuole, nucleus,
nucleolus, chloroplasts, cell wall, and cell membrane if they are visible.
PART C: IDENTIFYING UNKNOWN CELLS
13. Record your observations of the unknown specimens in the data table.
Classification of Unknown Specimens
Unknown
Classification
(code number) (plant or animal)
Reasons for
classification
14. Obtain prepared slides of three unknown specimens from your teacher.
15. Observe each specimen under low and high power. In the data table, record
the code number assigned to each unknown, each specimen’s classification as
plant or animal, and your reasons for classifying each specimen.
16.
Clean up your materials, and wash your hands before leaving the lab.
Analysis and Conclusions
1. According to your observations in this investigation, list several ways that plant
and animal cells are structurally similar and several ways that they are different.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Modern Biology
27
Datasheets for In-Text Labs
Back
Lesson
Print
Name
Class
Date
Comparing Animal and Plant Cells continued
2. What do you think might be the function of cytoplasmic streaming in a plant
cell? Lugol’s iodine solution causes cytoplasmic streaming to stop. Why do
you think this happens?
3. Which organelles that you read about in this chapter did you not see in this
investigation? Why do you think you were unable to see these organelles in
your slides?
Further Inquiry
Use library resources to locate electron micrographs of cell structures that you
were unable to see with the compound light microscope.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Modern Biology
28
Datasheets for In-Text Labs