Life Science Lab + The Microscope and Microscopy Techniques

The Scientific Method is the process of objectively establishing facts through observation, experimentation, and repetition.

• Step 1: Make an Observation

  • From your experiences, thoughts, or reading

• Step 2: Ask a question

  • Why does this phenomenon occur?

• Step 3: Formulate one or more hypotheses

  • What are the possible causes of this phenomen

• Step 4: Develop testable prediction(s)

  • If (hypothesis 1,2,3…) is the cause of this phenomenon, then I expect….

    IF, THEN statement

• Step 5: Design an Experiment

  • Only test one hypothesis per experiment

  • Independent variable: The cause- its value is independent of other variables in your study.

  • Dependent variable: The effect – its value is dependent on the changes within the experiment

  • Control variable: Any variable(s) that are held constant in a research study.

  • Experiments must be repeatable, with clear, transparent procedures

• Step 6: Collect Data

  • Record your results, challenges, and any changes to the procedure

• Step 7: Analyze the data

  • Statisitical Tests: T-Tests, ANOVA, Regression, etc

    • T-test: compares the two means in a group

    • ANOVA: compaes the mean across 3+ groups

    • Regression: Anaylsis the relationship between two variables

  • Graphs: A visual representation of the data.

    • Independent variable on x-axis, dependent variable on y-axis

• Step 8: Draw conclusion(s)

  • Does your data support your hypothesis?

  • All data and conclusions even if our predictions are not supported

• What is a microscope?

  • An instrument used to see and enhance the resolution (clarity, sharpness) of an object.

  • Used to magnify an object that we cannot see with the human eye

  • Primary kinds of microscopes: Dissecting (stereo), Compound, SEM (Scanning Electron Microscopes), and TEM (Transmission Electron Microscope)

• Types of Microscopes

  • There are many different types of microscopes, including Dissection (Stereoscopic), Compound, Fluorescence, Digital, Automatic Imaging, Confocal, Phase Contrast, SEMs or (Scanning Electron Microscopes), and lastly TEMs (Transmission Electron microscope).

  • In LifeScience, however, we will learn about and use just two

    • The Dissection (Stereoscopic) Microscope

      • Light BOUNCES OFF the specimen

        • Used to view larger, thick, solid or opaque specimens

        • Used in the dissection of small animals

      • Defining characteristics

        • Often have a simple or no built-in light source

        • Two focus knobs

        • 1 or 2 ocular lens

        • Large specimen stage

    • The Compound Light Microscope

      • Light shines THROUGH the specimen

        • Used to view very small, thin, or transparent objects/specimens

        • Used to study the life histories and identity of microorganisms

      • Defining characteristics

        • Have a built-in adjustable light source

        • Coarse and Fine focus knobs

        • 1 or 2 ocular lens, Multiple objective lenses

        • Adjustable stage for specimens

      • Parts of the Stereo-microscope

        • Ocular Lens

          • Objective Lens

          • Zoom Knob

          • Focus Knob

          • Arm

          • Lights (Not always)

          • Stage

          • Base

        • Light is bounced off the specimen and reflected into the lens for viewing

• The Compound Microscope

  • Used for viewing at high magnification (4-1000x)

  • Magnifies the image twice

  • Composed of two or more lenses: a primary magnification lens (ocular) and a secondary lens system (objective)

  • Light is passed through an object and is then focused by the primary and secondary lens.

  • A compound Microscope has four different objective lenses:

    • 4x = Low Power

    • 10x = Medium Power

    • 40x = High Power

    • 100x = Oil Immersion

    • Ocular lens itself is approximately 10x

  • Parts of the Compound Microscope

    • Ocular Lens

    • Objective Lens (4x-100x)

    • Coarse Adjustment Knob

    • Fine Adjustment Knob

    • Stage Adjustment knobs

    • Condenser Lens

    • Specimen Clamps

    • Light Source

    • Arm

    • Stage (Mechanical)

    • Base

  • Compound Microscope – How Does it Work?

    • Light passes through primary and secondary lenses resulting in the viewed image becoming inverted and backward.

    • When adjusting, move the mechanical stage to the opposite direction from the desired field of view.

      • Left  Right

      • Right  Left

      • Up  Down

      • Down Up

• How to Prepare a Wet Mount

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