Required Practical Activity 1

Using a Light Microscope to Observe, Draw and Label a Selection of Plant and Animal Cells

Materials Needed:

• Light microscope
• Prepared microscope slide containing plant and animal cells
• Blank sheet of paper or science notebook for drawing
• Pencil or pen for drawing and labelling
• Ruler or stage micrometre (with known scale) for measuring

Safety Guidelines:

• Carry the microscope with both hands, one hand on the arm and the other supporting the base. Avoid placing heavy objects on top of the microscope or using it as a support.
• Use lens paper or a soft, lint-free cloth to clean the lenses before and after use. Do not use regular tissue or cloth, as it may scratch the lenses.
• Ensure the microscope is placed on a flat, stable surface to avoid accidental tipping.
• Avoid looking directly into the light source, especially when it’s at its highest intensity.
• Only use prepared microscope slides provided by your teacher.
• Handle the microscope slides by their edges to avoid leaving fingerprints or smudges on the glass.

Procedure:

1. Set Up the Microscope:
   1. Place the light microscope on a flat, stable surface.
   2. Plug in the microscope and turn on the light source.
   3. Lower the stage to its lowest position.
   4. Select the lowest magnification objective lens (usually 4x or 10x) and rotate it into place.
2. Prepare the Microscope Slide:
   1. Obtain a prepared slide containing plant and animal cells. These slides are available from science suppliers or can be prepared by your teacher.
   2. Place the slide on the centre of the stage, ensuring it is properly centred.
3. Focus the Microscope:
   1. Look through the eyepiece (ocular lens) and adjust the focus knob until you see a clear image.
   2. Use the coarse focus knob first, then fine-tune the focus using the fine focus knob. Move the stage up or down as needed to get the cells in focus.
4. Observe and Identify the Cells:
   1. Carefully observe the cells on the slide, first at low magnification (e.g., 4x or 10x).
   2. Identify and note the differences between plant and animal cells, such as cell wall (present in plant cells) and centrioles (present in animal cells).
5. Increase the Magnification:
   1. After observing the cells at low magnification, rotate the medium or high magnification objective lens (e.g., 40x or 100x) into place.
   2. Refocus the microscope using the fine focus knob to see more detailed structures within the cells.
6. Draw and Label the Cells:
   1. Prepare a blank sheet of paper or a science notebook for drawing the cells.
   2. Using a pencil or a pen, draw the observed plant and animal cells on the paper, ensuring you accurately represent their size and shape.
   3. Label the different structures you can see in the cells, such as the cell membrane, nucleus, chloroplasts (in plant cells), and other organelles.
7. Add a Magnification Scale:
   1. To include a magnification scale, use a ruler or a stage micrometre, which has a known scale.
   2. Measure the size of a known cell structure (e.g., the diameter of a cell or an organelle) on your drawing in millimetres.
   3. Divide the measured size in millimetres by the objective lens magnification to get the actual size of the structure in micrometres (μm). Write this information on your drawing.
8. Clean Up:
   1. Turn off the light source and unplug the microscope.
   2. Gently remove the microscope slide from the stage and return it to its storage container.

Remember, proper handling and care of the microscope will ensure your safety and prevent damage to the equipment. Always work under the supervision of your teacher or lab supervisor. If you encounter any issues with the microscope, inform your teacher immediately.