Practical 1 - Mircroscopes
S1: Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1)
Technical notes:
Microscope with eye piece graticules, Stage graticules, Post-it notes, prepared slides, newspaper, scissors, distilled water, clear slides, coverslips
Time: 2hrs
In this practical we:
1) introduce the microscope and it's features
2) Practice making slides using newspaper, cheek, onion and elodea tissues
3) Practice making measurements of specimens on slides
4) Practice making biological drawings of our specimens
5) Practice the skill of calculating magnification and specimen size
The microscope and it's features
Exercise 1: Using this video, add labels using post it notes to the different parts of the microscope.
Exercise 2: Using a pre-prepared slide try to focus on and identify the tissue on low, medium and high power.
Making slides & Taking measurements
Exercise 3: Following the video, take a clipping of a word from the newspaper, and mount this word on a clean slide, add some water and a coverslip. Try to identify the letters at different magnifications.
Now prepare two more slides following the protocols below:
Cheek cells
Take a clean cotton swab and gently scrape the inside of your mouth.
Smear the cotton swab on the centre of the microscope slide
Place the cotton bud in the bin
Add a drop of methylene blue solution and place a coverslip on top - do not add too much solution.
Remove excess solution by allowing a paper towel to touch one side of the coverslip
Place the slide on the microscope with the low or medium magnification lens find a cell.
Increase the magnification. What structures can you see?
Elodea cells
Pick an entire healthy looking Elodea leaf using your fingers or cutting the leaf off with small scissors.
Place the leaf on the microscope slide
Add a drop of water and a cover-slip
Increase the magnification. What structures can you see?
Write your initials on all the slides that you have prepared
Exercise 4: Taking measurements.
Using the eye piece scale:
Can you use the measuring scale on the eye piece to measure the dimension of a letter? How do the units on this scale change as you change the magnification?
Can you use the measuring scale on the eye piece to measure the length of your cheek and elodea cells? How do the units change as you change the magnification?
Now mount the stage graticule, following the information given on the video below, work out how many mm one eye piece unit measures at each magnification.
Making drawings
Exercise 5:
Now pick either the elodea or cheek cells slides and draw what you can see. Remember:
Include a title and date
Include a scale bar
Label any structures you can see
Draw using pencil and solid (not dashed) lines. Do not sketch or shade
Hooke's Micrographia
Calculating magnification
Exercise 6: Watch the video and complete the exercises
_calculating_magnificaiton[1].pdfMagnification 2.pdfMagnification_questions.docx