MODULE 1
Objective 1.2 Lesson B
Course
Advanced
Biotechnology
Unit
Biotech
Basics
Essential
Question
How do
scientists view
cells using a
light
microscope?
What are
model
organisms?
TEKS
130.364 1A-K,
5A-E, 9E
TAKS
Obj 1 2B, Obj
2 8C
Prior Student
Learning
Function of
the light
microscope/
types of cells
Introduction to the Microscope
Using the Light Microscope and Slide Preparation
Rationale
Most students have had some experience with a light microscope, but it was
probably brief. This is a good lab to introduce lab safety, protocols to follow in
class, lab expectations and a road map for becoming a better scientist. It also
emphasizes observation of finite details, a vital skill for any successful
scientist.
Objectives
Students will:
• Properly use a light microscope to view various types of cells.
• Prepare samples using wet mounts and gram staining.
• Identify bacterial cell types using an oil immersion lens.
• List similarities and differences between bacterial, animal and plant
cells.
• Discuss microscope applications and model organisms used in
biotechnology industry.
Engage
• Show students ways in which microscopes are useful in all
sectors of the biotechnology industry using the videos below.
Plant and animal applications have been selected to reinforce
comparisons between the types of cells.
1.
2.
3.
4.
Beating Stem Cells
In Vitro Germination
Cancer Cells in Action
Glowing Embryo
Key Points
• Refer to “How to Use the Compound Light Microscope”:
http://www.austincc.edu/biocr/1406/labv/microscope/index.html
Estimated
Time
1.5 hours
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Activity
1. Students complete the pre-lab section of Using the Microscope to
Survey Cells.
2. Review with students the correct way to use a bright field microscope.
3. Students should work in pairs and record observations and analysis
as they work through the lab activity.
4. Remind students the correct procedure to use when recording science
drawings:
5. Use pencil - you can erase and shade areas.
6. All drawings should include clear and proper labels (and be large
enough to view details). Drawings should be labeled with the specimen
name and magnification.
7. Labels should be written on the outside of the circle. The circle indicates
the viewing field as seen through the eyepiece. Specimens should be
drawn to scale - i.e., if your specimen takes up the whole viewing field,
make sure your drawing reflects that.
8. Complete Venn diagram assessment.
Assessment
• Results and analysis on student worksheets.
• Venn Diagram comparing plant/animal cells
Materials
• Lab: Using the Microscope to Survey Cells (Prepared slides can be
purchased from your science supply store. Elodea leaves and pond
water can be obtained from your local pet store.)
• Venn Diagram Rubric
Accommodations for Learning Differences
• Visit the Special Populations section of the CTE Career and
Technical Education Website: http://cte.unt.edu/special-pops.
National and State Education Standards
Science Standards
Texas College and Career Readiness Standards
I. C1, C2, C3, E1, E2
II. F1
III. B1, B2, B3
V. D1, E2
VI. A1, A2
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Using the Microscope to Survey Cells
PRE-LAB
Use the following websites to help you complete the pre-lab questions below:
• http://www.austincc.edu/biocr/1406/labm/ex3/prelab_3_8.htm.
• http://irtflash.austincc.edu/flvplayer/index.html?instructional/JLai&id=Microscope
1. Label the microscope parts in the figure below.
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2. Identify the part of the microscope being described below:
a. A series of lenses that focus light onto the specimen: ________________
b. The focus adjustment knob that should NEVER be used when the high power or oil
immersion objectives are in alignment: ________________________
c. Regulates the amount of light passing through the specimen: ______________
d. The lenses you look through: ______________________
e. The surface on which you place your slide: ________________
3. Are the statements below TRUE or FALSE? Correct statements that are false.
a. Always begin your observation of each slide with the low power or scanning objective in
viewing position.
b. If you cannot locate your specimen on low power, try switching to high power.
NEVER move the coarse adjustment knob when the high power or oil immersion objectives
are in viewing position.
c. When you are finished with your microscope, clean it off (use ONLY lens paper to clean
the lenses), rotate the high power objective into viewing position, raise the stage, and return
the microscope to the cabinet.
d. Clean the oculars and objectives of your microscope with special lens paper before each
use.
e. You may use paper towels to clean and dry the microscope slides.
Copyright © Texas Education Agency 2012. All rights reserved.
Lab: Using the Microscope to Survey Cells
Name: __________________
Industry Spotlight Video : Forensics and the Electron Microscope
• After viewing, record the main idea in a few sentences below.
I. Magnification
Each objective lens has several numbers engraved on its side. Usually, the first number indicates
the magnification of the objective while the second number indicates its numerical aperture (NA).
In the following Table, indicate which objectives are found on your microscope.
•
What happens to the length of the objectives as the magnification increases?
When you are viewing a fairly large specimen (easily visible with the naked eye) you can begin
with the scanning objective; otherwise, you should begin viewing each new slide with the low
power objective.
⇒NEVER BEGIN VIEWING A SLIDE WITH THE HIGH POWER OR OIL IMMERSION
OBJECTIVES!
Slowly rotate the nosepiece until you feel the low power objective click into place. The total
magnification of your microscope is calculated by multiplying the magnification of the ocular by the
magnification of the objective.
Ocular lens magnification X Objective lens magnification = Total Magnification
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Calculate the total magnification for each ocular/objective combination on your microscope:
Learn about the microscope stage on your microscope:
Place a clean microscope slide on the stage and fasten it securely between the stage clips or
clamps. If your microscope has a mechanical stage, 2 knobs located on the side or bottom of the
stage control movement of the slide. Try rotating each stage manipulator knob and note the
direction the slide moves.
Using the stage manipulator knobs, move the slide until the center is directly above the stage
aperture. If your microscope does not have a mechanical stage, you will have to move the slide by
hand until the center is directly above the stage aperture.
•
Does your microscope have a mechanical stage? _______________
•
Is the switch to turn on the illuminator a rheostat--that is, can you use it increase and
decrease the brightness of the light--or is it a simple on/off switch? _________
II. Diaphragm
•
Examine the diaphragm, what are the numbers written on it?
•
Which setting makes the specimen the lightest? _____The darkest? _____
III. Lenses and Knobs
•
Twist the ocular lens, does yours have a pointer?
•
Find out what happens to your viewing field if you do not have an objective fully clicked into
place. Record your observations:
_ What is the purpose of the pointer?
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Observe the action of the coarse focus and fine focus knobs:
With the low power objective in place, view the microscope from the side (do NOT look through the
ocular) and slowly rotate the coarse adjustment knob, being careful not to hit the slide with the
objective.
Depending on the type of microscope you are using, the focus knobs will raise and lower either the
stage or the body tube.
•
Which part of the microscope moves when you rotate the coarse adjustment?
________________________________________________________________________
Now rotate the fine adjustment knob.
•
How does the movement when rotating the fine focus knob compare to the movement you
observed when using the coarse focus knob?
________________________________________________________________________
With the dual-viewing microscopes, the person using the SIDE ocular should focus the image
using the coarse and fine adjustment knobs. Once these adjustments are made, the person using
the TOP ocular can make additional fine adjustments for his/her own eyesight by rotating the tube
that supports the top ocular.
IV. Viewing a Slide
Procedure:
1. Obtain a prepared E slide. Focus the slide first with the scanning objective, then click to
lower power and focus again. Finally, focus the slide under high power. Remember, at high
power, you should only use the fine adjustment knob.
2. Draw the E exactly as it appears in your viewing field for each magnification. The circles
below represent your viewing field. The E should take up as much space in the drawing as it
does in your viewing field while you're looking at it.
When Drawing Specimens:
1. Use pencil - you can erase and shade areas.
2. All drawings should include clear and proper labels (and be large enough to view details).
Drawings should be labeled with the specimen name and magnification.
3. Labels should be written on the outside of the circle. The circle indicates the viewing field as
seen through the eyepiece. Specimens should be drawn to scale - i.e., if your specimen takes up
the whole viewing field, make sure your drawing reflects that.
Copyright © Texas Education Agency 2012. All rights reserved.
Scanning
Low Power
High Power
Analysis:
1. How does the letter “e”, as seen through the microscope, differ from the way an
“e” normally appears?
2. When you move the slide to the left, in what direction does the letter “e” appear to
move? When you move it to the right? Up? Down?
3. How does the ink appear under the microscope compared to normal view?
4. Why does a specimen placed under the microscope have to be thin?
5. Why is it important to focus on low power first?
V. Depth Perception
Industry Spotlight: Beating Stem Cells
•
After viewing, record the main idea in a few sentences below:
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Procedure:
1. Obtain a prepared thread slide. You will only need to view it under scanning at this point. Your
task is to figure out which thread is on top, which is in the middle, and which is on bottom. You
should notice that as you focus the thread, different thread will come into focus at different times.
The one that comes into focus first should be the top thread.
What is the color order of your threads?
VI. Making a Wet Mount of a Slide: Elodea Leaf (Plant)
Industry Spotlight: In Vitro Germination
•
After viewing, record the main idea in a few sentences below:
Procedure:
1. Obtain an Elodea leaf. If your specimen is too thick, then the cover slip will wobble on top of the
sample like a see-saw, and you will not be able to view it under high power.
2. Place one drop of water directly over the specimen. If you put too much water, then the cover
slip will float on top of the water, and unwanted movement will make it difficult to draw the
specimen.
3. Place the cover slip at a 45-degree angle (approximately) with one edge touching the water
drop and then gently let go. Performed correctly, the cover slip will perfectly fall over the
specimen.
4. Draw the specimen as it appears in your viewing field under scanning, low and high power.
Scanning
Low Power
High Power
Low Power
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Analysis:
1. Was anything moving in your cell? Explain the source.
2. What structures were you able to identify in the plant cell? Be sure to label them in your
drawings.
VII. Staining a Specimen: Cheek Cell (Animal)
Industry Spotlight: Cancer Cells in Action
•
After viewing, record the main idea in a few sentences below:
Industry Spotlight: Glowing Embryo
•
After viewing, record the main idea in a few sentences below:
Procedure:
1. Place a small drop of Iodine onto a clean slide.
2. Using a toothpick, gently scrape the inside of you cheek.
3. Place the toothpick tip into the iodine and mix. The iodine stains the cells so you can see them.
4. Draw your specimen as it appears under low power. Use color pencils to show how the stain
appears. It may appear darker or lighter in spots. Use shading to show darker and lighter spots.
Copyright © Texas Education Agency 2012. All rights reserved.
Scanning
Low Power
High Power
Analysis:
1. Why did we add iodine to our cheek cells?
2. What structure in the cheek cell was stained the darkest?
3. What structures were you able to identify in the animal cell? Be sure to label your drawing,
VIII. Investigation of Pond Water and Microorganisms
Industry Spotlight: Algae Biofuels
•
After viewing, record the main idea in a few sentences below:
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Procedure:
1. Prepare a wet mount of pond water - a sample of pond water is provided in a jar. The best
specimens usually come from the bottom and probably will contain chunks of algae or other
debris that you can see with your naked eye. (Be careful that your slide isn't too thick.)
2. Use the microscope to focus on the slide - try different objectives; some may be better than
others for viewing the slide.
3. Make three separate drawings below at different areas of the slide and at different
magnifications. Label where appropriate.
4. Obtain preserved slides of various microorganisms and specimens. Draw your specimens,
and label with the name of the specimen and the magnification.
Scanning
Low Power
High Power
Scanning
Low Power
High Power
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IX. Observing Prepared Slides (Bacteria)
Procedure:
1.
2.
Obtain 3 bacterial slides from your teacher.
Draw and label your specimens below at the magnification that is most visible.
Specimen 1
Specimen 2
Specimen 3
Analysis:
1. List two (2) observations you made that could be used to determine this is a bacterial cell.
Copyright © Texas Education Agency 2012. All rights reserved.
Venn diagram: Create a Venn diagram of plant and animal cells. Remember, things that
are common between the two cells types go in the overlapping area. Things that are unique
go in the non-overlapping areas.
VENN DIAGRAM RUBRIC
Fair
Good
Lab Support
Poor
Good
All statements are
supported by the lab.
Statement Placements
Good
All statements noting
similarities are placed in
the center circle and all
statements that note
differences are placed in
the correct outer circle.
Number of Quality
Statements
Good
Student is able to make five
or more comparison
statements in each circle.
Fair
Most statements are
supported by the lab.
Fair
Most statements are
placed in the correct
circle, but student mixed up
a few statements.
Fair
Student is able to make
3-4 comparison statements
in each circle.
Poor
Few or none of the
statements are supported by
the lab.
Poor
Few statements are
placed in the correct
circle.
Poor
Student makes two or
few comparison
statements in each circle
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