unit 1 24-38

Biology (Science II)

Unit I: The Nature of Biology

Time Frame: 1 week and 3 days

Competencies

4. Know how to operate the compound microscope

4.1 Identify the parts of the compound microscope4.2 give uses of the compound microscope4.3 name the special tools in research and technology

Lesson 6. The Compound Microscope

I. Subject Matter: The Compound Microscope

Time Frame: 3 periods

References:

Suggested Textbook:

University of the Philippines Institute for Science and Mathematical Education Development. (1998). Sourcebook on practical work for teacher trainers: High school biology. (vol. 1). Quezon City: Author. pp. 107-109; p. 111 part E.

Rabago, L. M., Joaquin, C. C. & Lagunzad, C. B. (1999). Science and technology: Biology. Laboratory Manual and Workbook. Quezon City: SD Publications, Inc. pp. 116-121.

For Further Reading:

Campbell, N. A., Mitchelle, L. B. & Reece, J. B. Biology: Concepts and connections. (3rd ed.) Singapore: Pearson Education Asia.

Levine, J. S. & Miller, K. R., (1991). Biology: discovering life. Mass.: D. C. Heath.

Rabago, L. M., Joaquin, C. C. & Lagunzad, C. B. (1997). Science and technology: Biology. Quezon City: SD Publications.

II. Objectives:

1. Give a brief history on the invention and development of the microscope2. Identify parts and functions of the compound microscope3. Compare the images of objects seen by the unaided eye and through the

microscope

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4. Differentiate various types of compound microscopes from each other5. Recognize the importance of the microscope in the study of biology6. Handle and maintain the microscope properly7. Identify special tools in research and technology

III. Materials:

A. For Teaching

Illustrations or actual examples of the different types of compound microscopesEnlarged illustrations from references listed in “For Further Reading”

B. For Student Activities

Compound microscopes ½ sheet of white paperLens paper BallpenTissue paper Ruler

IV. Lesson Proper:

A. Recall

Instruct the students to do the following:“Close your eyes and try to remember the image of any object/specimen that you have first viewed under the microscope.”

Then, let one or two students describe what they have remembered. Refer to this description during the discussion on the differences in the image of an object seen by the unaided eye and under the microscope

B. Motivation

Show students the illustration of a specimen seen under the microscope below. Let them point out which one is viewed under the scanner and under the Low Power Objective (LPO). You may reward those who are able to identify them correctly with simple or inexpensive prize/s.

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Start the lesson proper with brief question and answer sort of discussion on the early beginnings and development of the microscope. Some students assigned to do advanced readings may share to the class about the different types of the compound microscope.

C.Activity

Check the workability of the microscopes before the activity. If the number of microscopes available is enough for 4 or 5 groups, let them do it by groups. Otherwise, a demonstration by some students will do. Each student though, should answer the developmental questions.

For Activity 6.2 emphasize the careful turning of the coarse or fine adjustment when using the HPO to prevent accidental crashing into the stage or glass slide when they do observations later.

D. Postlaboratory Discussion

Answers to Developmental Questions in Activity 6.1.

Question 1. How many objectives does your microscope have?Answer: Three, some may have four.

Question 2. Do they have the same length?Answer: No.

Question 3. How are the numbers related to the length of the objectives?Answer: The higher the number, the longer the objective.

Question 4. Which is the scanner? The low power objective (LPO)? The high power objective (HPO)?

Answer: The scanner is usually marked 4x; in some, these are marked 3x or 5x. the LPO is usually marked 10x; some maybe 12x, 15x or 20x. HPO is usually marked 40x; some 43x, 45x or 60x.

Question 5. Does it have the inscription 97x, 100x or OIO or the word “oil” on it?Answer: There is no oil immersion objective (OIO). (The answer is yes if

there is an OIO).

Question 6. In what direction must the coarse adjustment knob be moved to raise the body tube?

Answer: Upwards or counterclockwise.

Question 7. How do you know when the objective is in position?Answer: It clicks.

Question 8. What is the function of the mirror?Answer: It reflects light up the microscope.


Question 9. How do they differ?Answer: One side is concave, the other plane.

Question 10. Which mirror is best to use for natural light?Answer: Concave mirror.

Question 11. What do you think is the use of the diaphragm?Answer: It is used to regulate the amount of light passing through the

microscope.

Question 12. In what direction should you rotate the disc to do this?Answer: Clockwise

In step 8, note that the diaphragm can also be referred to as rotating disc diaphragm or iris diaphragm. The iris diaphragm has a lever which should be moved to the right to increase light or to the left to lessen light or to close it.

Take note that if an iris diaphragm is present in your microscope, the question after step 9 should be: in what direction should you turn the lever? And the answer should be to the left to lessen light or to close it.

For step 6 of Procedure C, if an iris diaphragm is present, it should read: Turn the lever to the left to close it.

Answers to Developmental Questions in Activity 6.2.

Question 1. How do the lines as seen under the microscope compare with the way you see them with the unaided eye?

Answer: As viewed, with the unaided eye, borders look like straight lines. Under the microscope, lines are bigger and irregular with holes and grooves.

Question 2. To which direction do you see the square move?Answer: It moves toward the opposite direction.

Question 3. Why do you have to watch from the side while the objective is being changed?

Answer: Objectives are of different lengths. This is done to prevent accidental crashing into the slide and breakage of objective lens and slide.

Question 4. Is the image still clear and well-focused?Answer: This will depend on whether the microscope is parfocal.

Question 5. Why should the fine adjustment be used only with the HPO?Answer: The fine adjustment moves slower (or shorter in terms of distance

as in stairs whose steps are closer to each other) than the coarse adjustment knob (as in stairs with steps a little farther away from each other).


Question 6. Do you see the full 1 mm square?Answer: No.

Question 7. Compare what you see with what you have observed under the HPO.

Answer: Under the scanner, the whole square can be seen. Under the LPO, only a small portion can be viewed while in the HPO, you may need to move the paper to see only a small portion of the line which has been enlarged and with the holes or irregularities of the line shown.

Question 8. Is the field of view using the HPO larger or smaller?Answer: It is smaller because only a small portion of the square is seen.

Question 9. Is the light brighter or darker under the HPO than it is under the LPO?

Answer: It is darker.

Question 10. If the magnifying power of the eyepiece is 5x and that of the LPO is 10x, how much is the object under them magnified?

Answer: 5x multiplied by 10x is equal to 50x.

Question 11. By how much is the object you are now viewing magnified?Answer: Answer depends on what eyepiece and objective are currently

used. If the eyepiece is 10x and scanner is 5x, then it is magnified 50x. If eyepiece is 10x and the objective used is 10x, then, it is magnified 100x (or 100 times).

Question 12. Can you now say that the microscope is an important tool in the study of biology? Explain.

Answer: Yes, the use of the microscope in biology enables one to see an enlarged view of objects/organisms for a thorough study of their structure and function. It also has the advantage of making one see organisms that are not visible using the unaided eye.

Then, point out some measures and practices to ensure efficient

and longer use of the microscope as enumerated below:

1. Check the microscope before and after use.. Report any missing or damaged part.

2. Use a clean tissue paper or soft cloth to clean the mechanical parts of the microscope.

3. Prevent liquids, especially acids and alcohol from coming in contact with any part of the microscope. Always use a cover slip in observing wet mounts.

4. Check for moisture (such as condensation of human breath) in the eyepiece. This may be due to prolonged observation of specimen. Wipe with tissue paper or soft cloth.


5. Avoid tilting the microscope while observing wet mounts. Select a chair with suitable height so that both forearms can be rested on the table during observation.

6. Never store microscopes in a chemical laboratory or any place where there are corrosive fumes. Make sure there are silica gel pack inside microscope boxes or storage cabinet to absorb moisture.

Discuss on more advanced tools for research and technology. Some of these worth mentioning are the phase-contrast microscope and the transmission, and scanning electron microscopes (TEM and SEM).

E. Generalizations:

1. The microscope enables one to study objects too small to be seen and observed by the unaided eye.

2. Various types of microscopes make possible the study of different specimens

from transparent, thin to opaque and ultra structures of the cell.

3. The compound microscope uses light and lenses to magnify objects/specimens. Total magnification of the microscope is computed by multiplying the magnifying power of the eyepiece by that of the objective.

F. Valuing and Application

Having learned about the usefulness of the microscope, inculcate in students the value of appreciating the efforts of those who first invented the microscope and the equipment’s capacity to enable us to discover the wonders of the world around us. You may ask students to recall any important information known to man due to the help of the microscope. Also, mention their responsibility in using properly and taking care of this important tool in the study of biology.

G. Assessment

Use any three of these questions in the lesson assessment.

A. Answer briefly:

1. A classmate of yours has just used the high power objective but unfortunately the objective has crashed into a prepared slide and broke it. What do you think went wrong with the use of microscope? What could have been a better/correct way to do it?


Answer: The student may have failed to look from the side while moving the HPO to focus on the specimen, or he may have used the coarse adjustment knob to move down the HPO or he may have moved the fine adjustment too fast and was not able to monitor the distance of the objective from the slide. If he wanted to use the HPO, he could have looked from the side and used the coarse adjustment knob to move the objective down. He should have stopped when the objective has almost touched the slide. Then, looking through the eyepiece he should have slowly turned the fine adjustment knob up or down until he sees the image clearly.

B. Multiple choice. Select the best answer.

1. Josan is using a compound microscope to examine a drop of pond water. Which objective will she use if she wants to see the greatest number of organisms in her sample?

a. high power objective c. oil immersion objectiveb. scanner d. low power objective

Answer: b. scanner

2. A student is looking at a pollen under the microscope. If the eyepiece of the microscope he is using has the inscriptions 5x and 45x for the objective used, how many times is the pollen magnified?

a. 9x c. 50xb. 40x d. 225x

Answer: d 225x

3. A researcher wants to study the mitochondria of the liver cells of the mouse. The best microscope for him to use is the:

a. scanning electron c. transmission electron microscope

b. phase-contrast d. binocular compound microscope

Answer: c transmission electron microscope


4. If a microscope has an objective with an inscription of 100x or 97x, it is called the:

a. oil immersion objective c. scannerb. high power objective d. low power objective

Answer: a oil immersion objective

V. Agreement:

The teacher can adapt any of these activities:

1. Assign students to look for pictures of the different kinds of microscopes from magazines, brochures or downloaded from the internet to be mounted on cartolina or illustration board. These can then be displayed on the walls or tables in the laboratory.

2. If the school library or nearby university subscribes to the American Biology Teacher, let students look up for the “Microscope Rap” in Vol. 54, No. 4 April 1982 issue. Let them try it and perform the rap in class.

3. Have students make an album of the different types of compound microscope. They should put captions under each picture or illustration as to its name, special feature and its use.


Activity 6.1 The Parts and Function of the Compound Microscope

For a student, familiarization with the parts and proper manipulation of the microscope will make the study of biology effective and enjoyable. In this activity, you will know about the different parts and function of this important tool in biology.

Objectives

1. Handle the microscope properly2. Identify the parts and function of the microscope3. Store the microscope properly

Materials

Compound microscope Tissue paperLens paper

Procedure

A. Handling the Microscope

1. Get the microscope from its case or the cabinet. Hold it by grasping the curved arm with one hand and supporting the base with the other hand. Always use both hands when carrying the microscope. The microscope should always be held upright.

2. Put the microscope down gently on the laboratory table. Place it 5-10 centimeters away from the edge of the able.

B. Identifying Parts and Function of the Microscope1. Study the diagram below. Locate the different parts of the microscope.

Parts of the Microscope


2. Examine the revolving nosepiece. Note that objectives are screwed into it. Microscopes may differ in the number of their objectives.

3. Look at the objectives closely. Notice the inscriptions on them, e.g. 4x, 10x, etc.

Question 1. How many objectives does your microscope have?____________________________________________________

Question 2. Do they have the same length?____________________________________________________

Question 3. How are the numbers related to the length of the objectives?____________________________________________________

Question 4. Which is the scanner? The low-power objective (LPO)? The high power objective (HPO)?____________________________________________________

4. Look at the longest or highest objective of the microscope that you have.

Question 5. Does it have the inscription 97x, 100x or 010 or the word “oil” on it?_____________________________________________________

If it does have one of these inscriptions, then it has an oil immersion objective (OIO). This objective is used when very high magnification is required as in viewing bacteria, fungi and very small protists.

5. Using the coarse adjustment knob, raise the body tube.

Question 6. In what direction must the coarse adjustment knob be moved to raise the body tube?_____________________________________________________

6. Looking from the side of the microscope turn the revolving nosepiece until the LPO is back in position.

Question 7. How do you know when the objective is in position?______________________________________________________


7. Look into the eyepiece. Practice viewing by using both eyes open. This will not tire the eye and other facial muscles. Tilt the mirror until you see a bright circle of light. This lighted circle is called the field of view of the microscope.

Question 8. What is the function of the mirror?______________________________________________________

Question 9. Feel the two surfaces of the mirror. How do they differ?______________________________________________________

If you are using natural light from the windows, try using both sides of the mirror with the LPO.

Question 10. Which mirror is best to use for natural light?______________________________________________________

8. Locate the diaphragm. Rotate it until the smallest opening is directly under the hole in the stage. While looking into the eyepiece, rotate the diaphragm to the next bigger opening. Continue to do so until the smallest opening is back under the hole in the stage.

Question 11. What do you think is the use of the diaphragm?

_______________________________________________________

9. Rotate the diaphragm to its largest opening.

Question 12. In what direction should you rotate the disc to do this?_____________________________________________________

10. If the lenses of the eyepiece are cloudy or dusty, wipe them gently with a piece of lens paper. Use tissue paper to wipe off the dust from the metal parts of the microscope.

C. Storing the microscope.

Every after use, prepare the microscope for storage following these steps:

1. Raise the objectives using the coarse adjustment knob.2. Lift the stage slips to remove the slide.3. Turn the revolving nosepiece until the LPO is in place.4. Bring down the body tube so that the lower end of the objective is approximately 1

cm above the stage.5. Position the clips so that they do not extend beyond the sides of the stage.6. Rotate the diaphragm until the smallest opening is in position.7. Position the mirror on its edge with the concave side facing the user to protect it

from dust.


8. Some microscope boxes have a socket for the eyepiece. In this case, remove the eyepiece from the body tube and place it in the socket.

9. Put back the microscope’s plastic cover. If the original plastic cover has been lost or destroyed, use any clean plastic bag big enough to cover the microscope.

10. Carry the microscope as described in Procedure A and put it back in its case or storage cabinet.

Source:

University of the Philippines Institute for Science and Mathematics Education Development. (1998). Sourcebook on practical work for teacher trainers: High school biology. (Vol. 1). Quezon City: Author pp. 107-109; p. 111 Part E.


Activity 6.2 Working with the Compound Microscope

After familiarizing yourselves with the parts and function of the microscope you will now use this biological tool to examine objects under it.

Objectives

1. Focus the microscope properly2. Compare the image and object seen by the unaided eye and under the microscope3. Compute for the magnification of objects seen under the microscope4. Recognize the importance of the microscope in the study of biology

Materials

Compound microscope1/8 sheet of white paperBlack ball pen

Ruler

Procedure

1. Draw one (1) mm square on the piece of white paper.

2. Place it on the stage of the microscope. Make sure the square is directly on the hole of the stage.

3. Looking from the side, carefully lower the body tube until the low power objective almost touches the paper.

4. Look through the eyepiece and with the coarse adjustment knob, raise the body tube slowly. Stop when you see the lines clearly, which means you have focused it already.

5. Turn the fine adjustment knob to get a clearer image.

Question 1. How do the lines as seen under the microscope compare with the way you see them with the unaided eye?__________________________________________________________

6. Look again through the eyepiece. Move the paper forward, then, backward, to the right and to the left.

Question 2. To which direction do you see the square move?__________________________________________________________


7. Center the square again. Looking from the side, carefully shift to the high power objective. You may need to raise the body tube to do this. Then, lower the HPO using the coarse adjustment knob till the objective almost touches the paper. Then, looking through the eyepiece and using the fine adjustment knob slowly raise the objective till you see the lines.

Question 3. Why do you have to watch from the side while the objective is being changed?__________________________________________________________

8. Now, look through the eyepiece.

Question 4. Is the image still clear and well-focused?__________________________________________________________

In many modern microscopes, the image is brought into clear focus under the low power objective, it will remain focused even after shifting to HPO. These microscopes are said to be parfocal.

If the image seen under the microscope is not in focus when changing from LPO to HPO, turn very slowly the fine adjustment knob in either direction to get a clear picture.

Question 5. Why should the fine adjustment be used only with the HPO?_________________________________________________________

9. Look through the eyepiece again.

Question 6. Do you see the full 1 mm square?__________________________________________________________

10. Shift to the LPO and scanner.

Question 7. Compare what you see with what you have observed under the HPO.____________________________________________________________________________________________________________________

Question 8. Is the field of view using the HPO larger or smaller?__________________________________________________________

Question 9. Is the light brighter or darker under the HPO than it is under the LPO?__________________________________________________________


11. Now, look at the inscription on the eyepiece and scanner. You should know that an object is magnified or enlarged by both the lenses or the eyepiece and objective. To know how much an object is magnified under the microscope multiply the eyepiece’s magnifying power by that of the objective being used. This will give you the total magnification of the object in focus.

Question 10. If the magnifying power of the eyepiece is 5x and that of the LPO is 10x, how much is the object under them magnified?_________________________________________________________

Question 11. By how much is the object you are now viewing magnified?__________________________________________________________

Question 12. Can you now say that the microscope is an important tool in the study of biology? Explain.____________________________________________________________________________________________________________________


unit 1 24-38

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