Lecture Notes: Microscopes and Protists

Introduction to Microscopes

• Discussion begins with a humorous exchange about protists on the kitchen table.
• Key protists mentioned: Euglena, Paramecia
• Importance of cleanliness in experimental setups.

Understanding Microscopes

Key Terms

1. Magnification
   • Refers to how much larger an object appears.
2. Resolution
   • Ability to distinguish between two objects.
   • Example: A microscope with 0.2 microns resolution can distinguish objects 0.2 microns apart.

Types of Microscopes

Light Microscopes

• Commonly used in classrooms.
• Brightfield Microscopes:
  • Dark image on a light background.
• Darkfield Microscopes:
  • Uses a light stop to block most light, showing only reflected or refracted light from objects in the specimen.
• Various types of light microscopes include:
  • Phase-contrast (detail of living specimens)
  • Laser-based models
  • Importance of choosing the right type for specific observations.

Electron Microscopes

• Used for observing smaller structures like viruses.
• Transmission Electron Microscopes (TEM):
  • Best for visualizing internal structures.
• Scanning Electron Microscopes (SEM):
  • Ideal for 3D surface visualization.

Brightfield Light Microscope Anatomy

• Key components:
  • Light Source: Provides illumination.
  • Condenser Lens: Focuses light on the specimen.
  • Diaphragm: Adjusts light level.
  • Objective Lenses:
    • Scanning (4x), Low Power (10x), High Power (40x).
  • Eyepiece Lens: Typically magnifies 10x.
• Total Magnification Calculation:
  • Example: Scanning lens (4x) x Eyepiece (10x) = 40x total magnification.

Focusing Mechanisms

• Coarse Focus Knob:
  • Moves the stage dramatically for rough focusing.
• Fine Focus Knob:
  • Allows for small adjustments to achieve precise focus.
• Stage Knobs:
  • Move the stage side to side for specimen exploration.

Preparing a Microscope Slide

1. Wet Mount Technique:
   • Involves adding a drop of sample to a slide and covering it with a slip.
2. Avoiding Air Bubbles:
   • Mention of air bubbles being misleading under the microscope.
3. Securing the Slide:
   • Use stage clips.

Observing Specimens

• Start with low magnification to locate the specimen then adjust to higher magnifications.
• Always be cautious with the slide and stage movement to avoid damaging the slide or lens.

Tips for Using Microscopes

1. Handle with Care: Glass slides can break.
2. Focus Awareness: Be mindful of the slide's position to avoid crushing.
3. Cleaning: Use lens paper instead of regular tissue to clean lenses.

Conclusion and Applications

• Microscopes reveal a world beyond the naked eye.
• Applications in life sciences:
  • Studying mitosis in onion root tips.
  • Observing stomata for plant responses.
  • Investigating osmosis in plant cells.
• Encouragement to stay curious and explore the microscopic world.