Biopedia: Practicals

Practical - No1

Parts and functions of the microscope, and using microscope to observe specimens.

Recognize the parts and understand the functions of a light microscope.
Use the microscope in correct manner.
Prepare wet mounts of live tissues or cells.
Manipulate the microscope to observe specimens.
Calculate the magnification of objects.
Draw cells according to the appropriate size and the scale.
Determine the actual size of cells

Materials and Equipments

Simple light microscope with low, medium and high power objectives.
Clean dry slides and cover slips.
Beaker and watch glasses
Water sample from paddy field , hey infusion, pond water sample, onion epidermal peel
Paint brush and a razor blade
Ptactical book

Use of Compound light microscope

A compound light microscope is so called because it uses light and both ocular and objective lenses to view the object

Identification of parts

1.Eye piece (ocular lens): Top most series of lenses through which an

object viewed

2.Body Tube: Holds nose piece at one end and eyepiece at the other

end ,conducts light rays

3.Nose piece: Revolving device that holds objectives

Objectives:

4 . Low - power objective – Holds 10* lens used to view

the object in greater detail

5 . Middle-power objective – Holds lens used to view the object

6 . High - power objective _ Holds 40* or 45* lens used to view

the object in even greater detail

7. Stage clips: Hold slides in place on the stage.

8. Diaphragm or control lever: Controls amount of illumination used

to view the object.

9.Mirror: Give optimum illumination to the object for clear viewing

10.Arm: Supports upper parts and provides carrying handle.

11.Stage: Holds and supports microscope slides.

12.Coarse adjustment knob: Knob used to bring object into

aproximate focus used only with low

power objective .

13. Fine adjustment knob: Knob used bring object into final focus.

14.Base: The flat surface of the microscope that rests on the table.

If your microscope has mechanical stage.

15. Mechanical stage: A movable stage that aids in the accurate

positioning of the slide.

16. Mechanical stage control knobs: Two knobs that are usually

located below the stage.

• One knob controls forward / reverse movement.

• The other controls right / left movement.

Focusing Microscope

Lowest power

Turn nosepiece so that the lowest power lens is in straight   alignment over the stage.

  Always begin focusing with the lowest power objective lens.

  With  the coarse adjustment knob , lower the stage until it stops.

Place a slide of the letter" e "on the stage, and stabilize it with the clips.

If your microscope has mechanical stage , pinch the spring of the slide  arms on the stage ,and insert the slide.

Center the "e " as best you can on the stage. If your microscope has two  control knobs located below the stage to center the letter "e"

Again be sure that the lowest power objective is in place.Then ,as you look from the slide , decrease the distance between the stage and the tip of the objective lens until the lens comes to an autonomic stop or is no closer than 3mm above the slide.

  While looking into the eye piece , rotate the diaphragm to give the maximum amount of light.

Slowly increase the distance between the stage and the objective lens, using the coarse adjustment knob, until the letter e or object comes into  view,or focus.

Once the object is seen,you may need to adjust the amount of light.To increase or decrease the contrast,rotate the diaphragm slightly.Practice having both eyes open when looking through the eye piece. as it greatly reduce eye strain.

How to observe the onion epidermal peel.

Make thin epidermal peel of onion and place in water in a watch glass.

Transfer section of onion peel into a drop of water on the center of a clean glass slide by using a fine paint brush.

Hold the cover slip at the edge of the drop water , with the help of a mounting needle,and gently lower the cover slip, supporting with the needle onto the drop of water .Do not allow air bubbles to be trapped under the cover slip.

Place the slide on the stage of the microscope and move the low power objective into position.

Looking through the eye piece , move the slide to bring the object into position for study. adjust the mirror to give optimum illumination to the object for clear viewing.

Use the coarse focus knob to get the immage as clear as possible.

Study and note the structure visible.

Rotate the bojective holder and bring the medium power into position. A djust rhe focus to get a sharp immage.

Bring the high power into position.

Use the fine focus knob to make the image sharp.

Study and record what you observe under low , medium and high power.

Observe the samples employing proper microscopic techniques.

Demonstrate the determination of actual size of given cell and advice them to determine the size of a cell.

Observations

Onion epidermal peel - [ 1 X EP X OL ]

water sample from paddy field

Euglena -[ 1 X EP X OL ]

hey infusion

Paramecium -[ 1 X EP X OL ]

pond water sample

Amoeba - [ 1 X EP X OL ]

Practical - No 3

Title - Use of electron micrograph to understand the structure of cellular components

Objectives

Interprets the electron micrograph
Identifies the cellular components as seen by electron micrograph
Draws the cellular components accurately
Determines the size of each cellular components

Materials and Equipments

Electron micrograph of a bacterium cell
Electron micrograph of an animal cell
Electron micrograph of a plant cell

Instructions

Allow the students to observe the electron micrograph of a bacterial cell, an animal cell and a plant cell.

Students must be able to identify the organelles and their relative propotions

Observations

Practical No.5

Microscopic observations and identification of different types of animal tissues.

Objectives

1.Use the microscope to identify major animal tissues

2.Makes suitable drawings of observed animal tissues as seen through

the microscope according to the scale.

3.Differentiates the animal tissues according to their characters.

Materials and Equipments

Microscopes
Prepared slides of epithelial tissues

smooth tissues

striated muscle tissue

cardiac muscle tissue

coonnective tissues

Instructions

1.Allow students to examine the slides of each tissue under low,

medium and high power

2. Let students make suitable drawings to show the observed

characteristics of above tissue.

3.Instruct the students to record highlighting the identification

features of each tissue.

Epithelial tissues

Connective Tissue

Cartilege

Bones

Blood

Muscular Tissue

Skeletal Muscle

Longitudinal skeletal muscle is non-branching and can be identified by peripheral nuclei. The large white vertical lines are knife marks from sectioning (artifact).Bar = 250 Micron

Cardiac Muscle

This photomicrograph of the same tissue taken in phase

shows the striations and intercalated disks

(arrows) more clearly.

Bar =30 Micron

Nervous Tissue

Practical No.6

Identification of different stages of mitosis and meiosis using microscopic slides .

Objectives

Identifies the major stages of cells in the process of mitosis and meiosis.
Differntiates the behavior of chromosomes during the two types of cell division.

Materials and Equipments

Student microscope
LS onion root tips for study of mitosis
TS anther for study of meiosis

Instructions

Let students observe each of the slides under low, medium and high powers of the microscope respectively.
Ask them to identify the cells which show the main stages of mitosis and meiosis using the positions and shapes of the chromosomes.
Direct students to draw the observed stages of mitosis and meiosis in correct sequence.
Direct students to identify ,carefully the various positions and shapes of the chromosomes and the changes that take place.
Instruct the students to record highlighting the changes that occur in the nucleus and centrioles of cells undrrgoing mitosis and meiosis.