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					General Biology I
      Lab

Lab #1: Intro, Safety, and
      Microscopy

 Instructor: Kristine A. Cooper
            Introduction
­   This course is a separate, 1 credit
    laboratory related to the content
    covered in General Biology I lecture.

­   General Biology I is a pre- or co-
    requisite.
            Syllabus
­ Schedule
­ Required & optional materials

­ Attendance

­ Preparation for lab

­ Academic Integrity

­ Grading
       Course Structure
­   Generally, courses grade on a 50-50
    basis, as follows:
    – 50% of your grade is derived from 5
      quizzes, the lowest of which is dropped.
    – 50% of your grade is derived from two
      practicals.
        Course Structure
­   In this course, your grade will be
    calculated as follows:
    – 1/3 of your grade will be worksheets
      given at the beginning of the class and
      turned in at the end.
    – 1/3 of your grade will come from five
      quizzes (none dropped).
    – 1/3 of your grade will come from two
      practicals.
       Grading Specifics
­ Lab reports= 12 @ 25 points = 300 pts
­ Quizzes    = 5 @ 60 points = 300 pts
­ Practicals = 2 @ 150 points= 300pts



­   In general, there are NO makeups for
    practicals or quizzes!
    Accommodations will be made only in
    extreme circumstances.
              Quizzes
­ Quizzes will be given in the test center.
­ They must be taken ON TIME (refer to
  your syllabus for dates between which
  quizzes are available)

        Test center procedures
              Lab Safety
­   Personal protective equipment
    – Appropriate attire
­ Extinguishers, fire blankets, eye wash
  station, emergency shower
­ Chemical & biohazard safety

­ Food, drinks, cell phones

­ Injuries
     Lab Safety Contract
­   Please fill out both sides of the lab
    safety contract and place in a pile in
    the front of the room.
Course Introduction



  Questions so far?
          Week #1 - Experiment #3

            Microscopy
­   Competent use of the microscope is a
    must for biological study.

­   There is a big difference between
    using a microscope and using a
    microscope properly.
    Types of Microscopes
­ Compound Light Microscope
­ Stereoscopic (dissecting) microscope

­ Scanning Electron Microscope
      Compound Light
        Microscope
­ Common, we will use this most in the
  lab.
­ Compound means two or more lenses
  are included, one being the ocular and
  the other the objective.
­ These microscopes can be either
  monocular (one eyepiece) or binocular
  (two eyepieces).
Parts of the Light
  Microscope
       ­   Ocular
       ­   Body tube
       ­   Arm
       ­   Revolving nosepiece
       ­   Stage clips
       ­   Objective lenses
       ­   Stage stop
       ­   Aperture
       ­   Stage
       ­   Coarse adjustment knob
       ­   Diaphragm
       ­   Light source
       ­   Fine adjustment knob
       ­   Power switch
       ­   Base
        Compound Light
          Microscope
­   These microscopes use transmitted
    light, which passes through the
    specimen and to the lens.

­   The total magnification of a compound
    microscope is calculated by multiplying
    the magnification of the ocular lens by
    the magnification of the objective.
           Magnification
­   Calculating magnification
    – The ocular lenses in our microscopes are
      10x
    – The objective lenses are 4x (scanning),
      10x (intermediate), and 40x (high power).
    – Therefore, a microscope with a 10x
      ocular and a 40x objective will have a
      total magnification of (10 x 40)= 400x
Stereoscopic (dissecting)
      Microscope
           Used for viewing larger
             items, such as petri plates
             or small insects, etc.
           Most parts are similar to the
             previously described
             microscope, although the
             light sources differ.
           Magnification is between 10x
             and 40x.
Stereoscopic (dissecting)
      Microscope
           These microscopes use
             reflected or incident light,
             which is directed at the
             sample, or transmitted
             light as in the compound
             light microscope.
Scanning Electron
   Microscope
          ­   Most powerful
              microscope we will
              cover.
          ­   Capable of
              magnifying minute
              cellular structures.
          ­   15x to 200,000x
              magnification
          ­   Electrons are the
              energy source,
              lenses are
              electromagnets.
    Proper care and use
­ Microscopes are stored covered, with
  their power cords wrapped around
  them.
­ Carry microscopes CAREFULLY, with
  one hand under the base and another
  on the arm.
    Proper care and use
­ Microscope lenses can be cleaned
  with lens paper ONLY.
­ DO NOT USE PAPER TOWELS OR
  KIMWIPES AS THESE WILL
  SCRATCH THE LENSES.
     Proper care and use
­   Initially, assure that no objective lenses are
    in place. The microscopes should be stored
    this way.
­   Next, wipe your prepared slide clean with a
    Kimwipe (do not do this for wet-mount
    slides) and place it on the stage, under the
    stage clips.
­   Power on your microscope and rotate the 4x
    objective into place.
    Proper care and use
­ Look through the ocular and bring your
  image into focus using the coarse
  adjustment knob.
­ Raise the condenser to the highest
  position, then close the diaphragm
  fully.
­ Looking through the ocular, slowly
  lower the condenser until the image
  comes into focus.
    Proper care and use
­ Slowly open the diaphragm just until
  the entire field of view is illuminated.
­ These steps are necessary to set your
  microscope for optimum resolving
  power.
­ You can now attempt focusing with the
  10x.
     Proper care and use
­   Most microscopes are parfocal, meaning
    focus should be mostly maintained between
    objectives.
­   This means little adjustment should be
    necessary when switching between
    objective lenses.
­   It is important to NEVER use the coarse
    focus (fine only) with the high power 40x
    objective in place. You may break slides or
    damage the lens.
    Proper care and use
­ Microscopes must be cleaned and put
  away properly after use.
­ These are very expensive pieces of
  lab equipment and their abuse will not
  be tolerated.
Some important points
­ The distance between the specimen
  being studied and the objective lens is
  called the working distance.
­ This is very small with the 40x
  objective in place, which is why we
  only use the fine adjustment knob.
Some important points
­   With higher magnification microscopes,
    such as those with total magnifications of
    above 400x, the oil immersion technique is
    used.
­   A drop of oil with the same refractive index
    of glass is placed on the top of the slide
    between it and the objective lens. This
    reduces two refractive surfaces to one,
    reducing distortion of the image.
Some important points
­   Field of view is the size of the area of
    the sample that can be seen under a
    certain magnification.

­   An important relationship: as
    magnification increases, the field of
    view decreases.
Some important points
­ Depth of field is the thickness of the
  specimen that can be seen in focus at
  one time.
­ You may be able to see different
  aspects (levels) of the same sample at
  different levels of focus.
­ The higher the magnification, the
  shorter the depth of field.
        Resolving power
­   The ability to see two objects of
    comparable size next to each other
    and still differentiate them as two
    separate items.



           Lower          Higher
    Preparation of a wet
        mount slide
­ To make a wet mount, a glass slide
  and cover slip are needed.
­ A small amount of a water-based
  sample (or sample added to water) is
  placed on the center of the slide.
­ The cover slip is then gently lowered
  over the surface of the sample.
    Preparation of a wet
        mount slide
­ Don’t use too much sample.
­ Don’t get fingerprints all over the slide
  and cover slip.
         Today in Lab
­ Complete exercises 3.1 through 3.4 in
  your lab manual.
­ Complete your lab report worksheet
  and hand in before you leave today.

            QUESTIONS?

				
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