microscopy

• What is the aim of the practical in AQA GCSE Biology?

  To use a light microscope for observations
• What are the main objectives of using a light microscope in the practical?

  • Observe plant (onion) and animal (cheek) cells
  • Produce clear, labelled scientific drawings
  • Include an accurate magnification scale
• What key skills are assessed in the AQA GCSE Biology practical?

  Safe and correct use of a light microscope
• What skills are included in the assessment of the practical?

  • Preparing microscope slides
  • Making accurate observations of cells
  • Producing detailed biological drawings
  • Calculating and including magnification
• What is the first step in preparing a slide for observation?

  Place the specimen on a microscope slide
• Why should specimens be handled gently during slide preparation?

  To prevent damage to the specimens
• What are common specimens used in this practical?

  Onion cells and cheek cells
• What is the purpose of staining cells?

  To make cell structures more visible
• What stain is typically used for onion cells?

  Iodine solution
• What stain is typically used for cheek cells?

  Methylene blue
• What are some issues to avoid when preparing slides?

  • Prevent smudging the slide
  • Carefully lower the coverslip to avoid air bubbles
• How should a microscope be carried?

  With both hands, one under the base
• What is the recommended starting point for observing a specimen?

  Begin with the lowest power objective lens
• What are the types of lenses in a light microscope?

  • Eyepiece lens (fixed magnification, often x10)
  • Multiple objective lenses with different magnifications (e.g., x4, x10, x40)
• What are the key rules for biological drawings?

  • Use a sharp pencil with clear lines
  • Show relative size and shape of structures
  • Include accurate labels with straight lines
  • No artistic embellishments
• What is the formula for calculating magnification?

  Magnification = Eyepiece × Objective Lens
• What should be included in a drawing's magnification scale?

  • A scale bar representing a known length
  • The calculated magnification (e.g., x100)