Cells: the basic unit of life

Cells: the basic unit of life

LIFE SCIENCES GRADE 10 CAPS STRUCTURED, CLEAR, PRACTICAL HELPING TEACHERS UNLOCK THE POWER OF NCS KNOWLEDGE AREA: Life at Molecular, Cellular and Tissue Level TOPIC 1.2: Cells: The Basic Unit of Life A Brief Overview of the History of Microscopy SUMMARY OF PRESENTATION Introduction

Structure of the Microscope Care of the Microscope Use of the Microscope Magnification INTRODUCTION As we already know cells are microscopic.

What does this mean? INTRODUCTION Thats right ! Microscopic: refers to organisms that are so small that they are not visible to the naked. TERMINOLOGY TERM:

Microscopic DEFINITION: USE IN SENTENCE: refers to organisms that are Viruses and bacteria are so small that they are not microscopic. visible to the naked. INTRODUCTION

Scientists were able to see and study the cells because of a discovery of microscopes. Initially botanist and zoologist were only able to study, describe, draw and label only the external structure of macroscopic organism. This is referred to as the macroscopic view. What are macroscopic organisms?

INTRODUCTION Thats right Macroscopic: refers to organisms that are visible to the naked eye. TERMINOLOGY TERM: Macroscopic

DEFINITION: USE IN SENTENCE: refers to organisms that are Bees and butterflies are visible to the naked eye. macroscopic because you can see with your eyes only. INTRODUCTION: ROBERT HOOKE Robert Hooke, an

English scientists looked at cork tissue under a very simple microscope as shown alongside. He observed these cells in 1665. As shown in the insert he saw many box like compartments. He called these

compartments cells. Robert Hooke and his microscopic study INTRODUCTION: ROBERT HOOKE

The cork tissue comes from the cork plant. However all he managed to see were the cell walls of the cells. The cork cells were dead, therefore there was nothing inside these cells. INTRODUCTION: ANTON VAN LEEUWENHOEK He was a Dutch

scientist. He observed the bacteria under a simple microscope in 1674 as shown below. Anton van Leeuwenhoek Van Leeuwenhoeks simple microscope INTRODUCTION

Three scientist, Oken in 1805, Lamarck in 1809 and Dutrochet in 1824, independently stated that plants and animals were made up of cells. In 1838 Mathias Schleidan, a German scientist, was first to regard the cell as a structural unit of plants. Then in 1839, Theodor Schwann was the first to regard the cell as the structural unit of animals.

INTRODUCTION A German scientist, Purkinje, was the first to use the term protoplasm to describe the living contents of the cell. This was in 1839. Then 1859, another German scientist, Schultz,

was the first to describe the protoplasm as the physical basis of life. Finally, Rudolf Virchow, put forward the idea that new cells formed when existing cells divided. These scientist were able to make these discoveries as a result of advancement in the development of the microscope. INTRODUCTION: THE CELL THEORY These ideas mentioned in the previous two slides developed into what is known as the cell

theory. INTRODUCTION: THE CELL THEORY According to this theory: 1. 2. Every living organism is made up of cells. Every living cell comes from another. STRUCTURE OF THE LIGHT AND ELECTRON MICROSCOPE

With your microscope at school you are able to see objects magnified 600 times, by using the 40X objective and 15X ocular lens. The nucleus, cell membrane, cytoplasm and chloroplast were observed and named using the light microscope. However the details of these structures were not visible because the microscope is not powerful enough.

STRUCTURE OF THE LIGHT AND ELECTRON MICROSCOPE However in the 1930s a more powerful microscope was invented by Zworykin. This was called the electron microscope STRUCTURE OF THE LIGHT AND ELECTRON MICROSCOPE

There are 2 types of electron microscopes. They are the scanning electron microscope (SEM) and the transmission electron microscope (TEM) The SEM is used to scan and view the surface of objects. The TEM is used to see inside the objects by allowing light to pass through them. STRUCTURE OF THE LIGHT AND ELECTRON MICROSCOPE

Electron Microscope With the electron microscope we are able to view objects 50 000 to 100 000 times. The image is clear and not blurred.

They are able to provide such good images because they use electron beams instead of light STRUCTURE OF THE LIGHT MICROSCOPE Parts of the Light Microscope STRUCTURE OF THE LIGHT MICROSCOPEPARTS AND THEIR FUNCTIONS. 1. 2.

Base: supports the microscope. Always place your hand under the base when transporting the microscope. Mirror: provides source of natural light. The mirror must be focused to reflect light. Parts of the Light Microscope

STRUCTURE OF THE LIGHT MICROSCOPE 3. 4. 5. Illuminator/lamp: it provides an electric source of light, it is much easier to use. The condenser: it is found below the stage. Its

function is to concentrate the light through the slide and specimen. Iris diaphragm: this is an opening in the condenser, it controls the amount of light falling on the specimen. Parts of the Light Microscope STRUCTURE OF THE LIGHT MICROSCOPEPARTS AND THEIR FUNCTIONS 6. 7.

8. Stage: this is the platform on which the slide is placed. Stage/slide clips: these are metal clips that are used to hold the slide in position so that is does not move around when it is being focused. Mechanical stage: this is found in only some

microscopes, it allows easy movement of the slide. Parts of the Light Microscope STRUCTURE OF THE LIGHT MICROSCOPEPARTS AND THEIR FUNCTION 9. 10. 11. Objectives: these are a combination of lenses

used to magnify the specimen. There are 3 different types of objectives. 4X objectives: this is the short objectives. It magnifies the objectives 4X 10X objectives: this is the medium objective. It magnifies the specimen 10X. Parts of the Light Microscope

STRUCTURE OF THE LIGHT MICROSCOPEPARTS AND THEIR FUNCTIONS 12. 13. 40X objective: this is the long objective. It magnifies the specimen 40X The revolving nose piece: the objectives are attached to this nose piece. Ensures the objective is in

position when viewing the specimen. Parts of the Light Microscope STRUCTURE OF THE LIGHT MICROSCOPEPARTS AND THEIR FUNCTIONS 14. 15. Body tube: the eye piece and objectives are found on it. It also links the eye piece and objectives. In other words it links and supports

the optical parts. Coarse adjustment screw: used to make adjustments to focus the image. It moves the body tube up and down quickly, it provides quick focus. Used mainly at low magnification. Parts of the Light Microscope STRUCTURE OF THE LIGHT MICROSCOPEPARTS AND THEIR FUNCTIONS 16.

17. Fine adjustment screw: is used to make fine adjustments to focus the image. Used with higher magnification. Prevents damage to slide if any sudden movements are made during focusing. Eye piece/ocular: combination of lenses that are used to magnify

the specimen. There are 3 oculars 5X, 10X and 15X Parts of the Light Microscope SOMETHING FOR YOU TO DO SOMETHING FOR YOU TO DO: Use your notes and diagram of the microscope to label the diagram and provide the functions of the following parts: 1. A 2. C 3. E

4. I 5. M SOLUTION A. B. C. D. E. F. G. H. I. J.

Eyepiece Coarse adjustment screw Body tube Fine adjustment screw Nose piece Medium objective/10X Arm Long objective/40X Stage clip SOLUTION K. L.

M. N. 1. 2. 3. 4. 5. Diaphragm Base Light source Short objective/4x Eye piece-magnifies image

Body tube- supports and links optical parts Nose piece- attachment of objectives Stage- platform on which slide is place Light source- provides electrical light CARE OF THE MICROSCOPE Follow these guidelines when handling a microscope: 1. Transport the microscope by placing one hand under the base and the other holding the arm, 2. Work one hand width away from the edge of the work bench. 3. Use only soft tissue to clean the lens. 4. Always ask for help if you are unsure of anything

USE OF A MICROSCOPE Setting the light and condenser 1. 2. 3. Open the diaphragm fully. Look at the mirror. Notice that it has two surfaces: a plane one and a concave one. If the microscope has a built in condenser then have the plane surface of the mirror facing up. If the there is no condenser then the concave surface

must face up. Adjust the mirror so that it faces a source of natural light. E.g. A window, open door. USE OF A MICROSCOPE 4. 5. Select the lowest power objective by turning the nose piece until you hear or feel the object click into position. Place a sharp pencil on the mirror and focus until you obtain a sharp image of the pencil tip.

USE OF A MICROSCOPE Focusing at low magnification 1. 2. 3. 4. 5. Place the slide on the stage. Secure it using the clips. Look through the eyepiece and slowly turn the

coarse adjustment screw to focus the specimen. Slowly turn the fine power objective to focus a clearer image of the specimen. The slide may need to be moved to ensure the part of the specimen under examination is what you are seeing. USE OF A MICROSCOPE Focusing at higher magnification 1. 2. 3.

Move the next objective into position by carefully moving the nose piece until the objective clicks into position. If the specimen is not clearly visible then use the fine adjustment screw to obtain a clearer image. You may repeat the process using the next high power object if more detail is required. USE OF A MICROSCOPE Changing the eyepiece 1. The magnification can be increased by using higher power eyepieces. 2. Simply remove the existing eyepiece and replace

it with one that has higher magnification power. USE OF A MICROSCOPERECORDINGS Record what you see 1. Draw a diagram of what you see. 2. Draw and label exactly what you see, even if many aspects are missing. 3. In many cases you do not have to draw the entire image, only a portion of it. 4. Do not forget to indicate the scale of your drawing. For example if you used the medium power objective and the 5X eyepiece then your scale is 150 times(5X10) 5. Use a sharp pencil.

USE OF A MICROSCOPE- PACKING AND STORING 1. 2. 3. 4. 5. Remove the slide. The 4x objective must be in position. Replace the dust cover Place the microscope in the correct box. Store away.

MAGNIFICATION Magnification of the microscope when viewing an objective: In order to determine how many times the specimen viewed is magnified by we need to calculate the magnification of the microscope. We can do this by using the following formula: Magnification power of = magnification of eyepiece X magnification of microscope lens MAGNIFICATION

For example if you use the 10X eyepiece and the 40X objective then Magnification = 10 X 40 = 400X It is usually expressed as viewed under the microscope at 400X. MAGNIFICATION To determine the actual size of an object viewed under the microscope using the field of view approach.

The field of view is the circle of light that you see when looking through the eyepiece. The diameter maybe measured by viewing a ruler under the microscope. The diameter for the field of view and the lens on your microscope is about 4.5 mm or 4500m.m. MAGNIFICATION:

To calculate the length of the object you must determine the portion/fraction of the field it covers. This can only be done by determining the number of objects that can fit in the field of view. MAGNIFICATION For example look at the two field of views below. X

X X X X In the one on the right 4 of the object can fit in the field of view. Therefore one object occupies of the field diameter.

MAGNIFICATION Therefore the approximate length of the object can be calculated as follows: 4500 m X = 1125 mm X = 1125 m X = 1125 mm The approximate length maybe calculated using the formula: Approximate length of object = fraction X diameter of field

MAGNIFICATION To determine the magnification of a drawing. 1. You need the actual size of the object drawn and the actual size of the drawing. 2. Magnification of the drawing can be calculated using the formula: Magnification of drawing = drawing size object size MAGNIFICATION For example if your object has an actual length of 1115 m, and your drawing of that object has a m, and your drawing of that object has a length of 5 cm, then you ,can calculate magnification of drawing as follows: First the 5cm must be converted into m X = 1125 mm that is

5 X 10 000 = 50 000 m, and your drawing of that object has a m Then: Magnification of drawing = drawing size object size = 50 000/ 1115 = 45 m, and your drawing of that object has a m 3. MAGNIFICATION To determine the actual size of the object whose image or micrograph is viewed using a scale line. 1. Determine what the scale line measures. 2. Assume it represents 1 m.m.m. 3. Measure the scale line given in the drawing or

micrograph. ( lets say its 15mm) 4. Measure the length of the image in ;the drawing or micrograph. ( lets say its 50mm) 5. Now we can use the following formula MAGNIFICATION Actual size = measured length of object (mm) X length of scale line (m.m) measured length of scale line (mm)) = 50mm X 1 m.m.m m. 15mm = 3.3 m.m.m TERMINOLOGY

Macroscopic: refers to organisms that are visible to the naked eye. Microscopic: refers to organisms that are so small that they are not visible to the naked. Field of view: is the circle of light that you see when looking through the eyepiece QUESTION 1

1. The platform on which the slide sits is called the A. Base B. Stage C. Condenser D. diaphragm QUESTION 2 2.

Opening that controls the amount of light entering the microscope A. Base B. Stage C. Condenser D. diaphragm QUESTION 3 3. It concentrates light through the slide and specimen A. Base

B. Stage C. Condenser D. diaphragm QUESTION 4 4. The combination of lens to magnify the image from objectives and specimen A. Eyepiece B. Body tube C. Illuminator D. Mirror

QUESTION 5 5. It supports and links the optical parts. A. Eyepiece B. Body tube C. Illuminator D. Mirror QUESTION 6 6.

Provides support for the microscope A. Base B. Stage C. Condenser D. diaphragm QUESTION 7 7. Provides electrical light when switched on. A. Eyepiece B. Body tube

C. Illuminator D. Mirror QUESTION 8 8. Provides a source of natural light. A. Eyepiece B. Body tube C. Illuminator D. Mirror QUESTION 9

9. Attachment of objectives. A. Nose piece B. Mechanical stage C. Stage clips D. Fine adjustment screw QUESTION 10 10. Holds the slide in position on stage.

A. Nose piece B. Mechanical stage C. Stage clips D. Fine adjustment screw QUESTION 11 11. Allows for easy movement of slide A. Nose piece B. Mechanical stage C. Stage clips D. Fine adjustment screw

QUESTION 12 12. The picture below shows the microscope used by A. B. C. D. Robert Hooke Van Leeuwenhoek

Oken Lamarck QUESTION 13 The scientist who viewed cork cells under a simple microscope. A. Robert Hooke B. Van Leeuwenhoek C. Oken D. Lamarck 13.

QUESTION 14 The scientist that observed and described single celled organisms. A. Robert Hooke B. Van Leeuwenhoek C. Oken D. Lamarck 14. QUESTION 15 The electron microscope was invented by

A. Robert Hooke B. Van Leeuwenhoek C. Zworykin D. Lamarck 15. QUESTION 16 16. Calculate the magnification power of a microscope if you use the medium power objective and the 15X eyepiece.

A. 150X B. 75X C. 25X D. 20X QUESTION 17 17. Calculate the length of an object if it covers of the field of view, assume that the diameter of the field of view is 4500m.m A. 2250 m.m, and your drawing of that object has a m B. 2000 m, and your drawing of that object has a m C. 4500 m, and your drawing of that object has a m

D. None of the above QUESTION 18 18. Calculate the magnification of a drawing you have done if your drawing of the organism is 2500 m X = 1125 mm and your drawing of it is 7 cm long. A. 2507 m, and your drawing of that object has a m B. 28X C. 0,0028 D. 28 m, and your drawing of that object has a m

QUESTION 19 19. If you wanted to scan and view the surfaces of objects, you must use the A. Electron microscope B. SEM C. TEM D. Light microscope QUESTION 20 20.

If you wanted to see the inside of objects you would use the A. Electron microscope B. SEM C. TEM D. Light microscope SOLUTION 1. 2. 3. 4. 5.

6. 7. 8. 9. 10. B D C A B A C D

A C 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

B B A B C A A B B C

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