viewing the microbial world

Cards (48)

  • metric units
    used to express the sizes of microbes
  • meter (m)

    The basic unit of length in the metric system
  • 39.4
    one meter is equivalent to this in inches
  • micrometers
    metric unit in which the sizes of bacteria and protozoa are usually expressed
  • micrometer
    is one millionth of a meter
  • 1 µm in diameter
    A typical spherical bacterium (coccus) is approximately
  • 1 µm x wide 3 µm long

    A typical rod-shaped bacterium (bacillus) is approximately
  • nanometers
    The sizes of viruses are expressed in terms of
  • nanometer
    is equal to one billionth of a meter
  • 10 to 300 nm
    Most of the viruses that cause human diseases range in size from
  • Ebola virus
    a cause of viral hemorrhagic fever
  • Ebola viruses 

    can be as long as 1,000 nm (1 µm)
  • ocular micrometer
    When using a microscope, the sizes of microorganisms are measured using this
  • microscope
    is an optical instrument that is used to observe tiny objects, objects so small that they cannot be seen with the unaided human eye
  • the resolving power or resolution
    Each optical instrument has a limit as to what can be seen using that instrument
  • 0.2 mm
    The resolving power of the unaided human eye is approximately
  • simple microscope
    a microscope that contains only one magnifying lens
  • magnifying glass
    could be considered a simple microscope as images appear 3 to 20 times larger than the object’s actual size when using this
  • Leeuwenhoek’s simple microscopes
    had a maximum magnifying power of about x300 (about 300 times)
  • compound microscope
    a microscope that contains more than one magnifying lens
  • compound light microscope
    Because visible light is the source of illumination, a compound microscope is also referred to as
  • Compound light microscopes
    usually magnify objects about 1,000 times
  • 0.2 µm 

    The resolving power of a compound light microscope is approximately
  • wavelength of visible light
    It limits the size of objects that can be seen.
  • The eyepiece or ocular lens and objective lens
    the two magnifying lens systems in today's laboratory microscope
  • ocular lens
    with x10 magnification
  • scanning, low power, high power, and oil immersion
    four commonly used objective lenses
  • scanning
    with 4x magnification
  • low power

    with 10x magnification
  • high power
    with x40 magnification
  • oil immersion
    with x100 magnification
  • Total magnification
    is calculated by multiplying the magnifying power of the ocular lens by the magnifying power of the objective lens being used
  • photomicrographs
    are photographs taken through the lens system of the compound light microscope
  • brightfield microscope
    Because objects are observed against a bright background or “bright field, the compound light microscope is sometimes referred to as a
  • darkfield microscope
    If the condenser is replaced with what is known as a darkfield condenser, illuminated objects are seen against a dark background or “dark field”; the microscope is then called
  • Phase-contrast microscopes and Fluorescence microscopes
    Other types of compound microscopes include
  • Phase-contrast microscopes
    are used to observe unstained living microorganisms
  • Fluorescence microscopes

    contain a built-in ultraviolet (UV) light source
  • Electron microscopes
    enable us to see extremely small microbes such as rabies and smallpox viruses
  • electron beam
    the source of illumination