Biology A-Level Chapter 1

Summary:

This text provides an overview of microscopy techniques in Level Biology (CIE 9700), specifically for cell studies. When preparing specimens for observation under a light microscope, the samples need to be thin enough to allow light to pass through. The appropriate preparation method depends on the cellular material being viewed. Samples may require staining, as some cell structures are transparent or difficult to distinguish. The staining process involves air-drying the sample, heating it with a Bunsen burner flame, and applying the appropriate stain. When recording observations, biological drawings are made following conventions such as including a title, noting the magnification, using a sharp HB pencil on plain white paper, and drawing clear, single lines without shading. Drawings should be proportionate and fill as much of the page as possible, with label lines kept to one side and drawn with a ruler. Magnification, the factor by which an image is enlarged compared to the actual size of the specimen, can be calculated if both the image size and actual size are known. When working with measurements, it’s essential to use consistent units, remembering that there are 1000 nanometers in a micrometre, 1000 micrometres in a millimetre, and 1000 millimetres in a meter. In exams, it’s crucial to only draw what you see, not what you think you see, and using the eyepiece graticule helps ensure accurate size and proportions.

Excerpt:

Biology A-Level Chapter 1

1.1 The Microscope in Cell Studies YOUR NOTES

CIE A Level Biology (9700) exams from 2022 Resources
REVISION NOTES, TOPIC QUESTIONS, PAST PAPERS

CONTENTS
1.1.1 The Microscope in Cell Studies
1.1.2 Magnification Calculations
1.1.3 Eyepiece Graticules & Stage Micrometers
1.1.4 Resolution & Magnification
1.1.5 Calculating Actual Size

1.1.1 THE MICROSCOPE IN CELL STUDIES

Microscope Slide Preparation

• In order to observe cellular material in more detail, specimens can be prepared for viewing
  under a light microscope.
• Samples need to be thin enough to allow light to pass through.
• The type of preparation that is appropriate is dependent on the cellular material that needs
  to be viewed.