Microbiology Lab Exam 1 Review
(Microscopy, Fungi, Protozoa, Bacteria,
Algae/Cyanobacteria,) Questions
and Answers.
simple microscope - -a microscope that contains only one lens
-compound microscope - -microscope that allows light to pass through a specimen and
uses two lenses to form an image
-field of view - -how much of the specimen you can see
-depth of field - -how much of a vertical area remains in focus
-working distance - -how far the objective is from the slide
-low power objective - -provides a magnification of 10x and is the shortest objective
-high-dry objective - -40x; blue line; equipped with a phase ring allowing phase
contrast microscopy;
-oil immersion objective - -100x; white line; most widely used; used w/oil that makes a
continuous bridge b/w tip of objective and slide
-uses of oil in oil immersion objective - -allows more light to enter lens; improves
resolution
-refractive index - -the speed of light in a given medium compared to the speed of light
in a vacuum
-refracted - -light being bent as it passes into a medium of different density
-contrast - -ability to distinguish an image against the background
-magnification - -the amount the image is enlarged; As Mag increases- field of view
decreases-working distance decreases-amt of light decreases-depth of field decreases
-resolution - -- level of detail that can be observed
, -brightfield microscopy - -just using the microscope; staining usually; adjusting iris
diaphragm for better contrast
-darkfield microscopy - -used to get excellent contrast for live unstained specimens;
bright with black background; most of the light coming from condensor misses
objective, only light that passes through the specimen and is refracted passes into
objective giving the bright image
-Phase-contrast microscopy - -specimen is dark on a light background; used to increase
quality of the image instead of bright field microscopy of unstained specimens; use a
phase annular diaphragm under the condenser and a centering telescope
-Fluorescence Microscopy - -bright colored specimen on black background; absorption
of light at one wavelength and emission of light at another; used in performing direct
counts of bacteria
-diatoms - -produce cell walls of silica that resist decay and is mined for many uses
-heterocysts - -cyanobacteria that perform nitrogen fixation
-Properties of Algae and Cyanobacteria - -• Prominently (but not always) inhabit
aquatic environments
• Growth limited by amounts of available Phosphorus and Nitrogen
• can form blooms if abundant (toxins)
• Can be free-living or involved in symbioses
• Carry out oxygenic photosynthesis
-Properties of Algae - -• Eukaryotic
• Reproduction: sexual (most) and asexual (some)
• Classification: partly based on pigment production
• Some produce cell wall "armor" (dinoflagellates) or cell walls made of silica (diatoms)
-Properties of Cyanobacteria - -• Prokaryotic
• Reproduction asexual
• Many able to fix nitrogen
nitrogen gas ammonia
(N2 + 8 H+ + 6 e− → 2 NH3 + H2)
- This only occurs in heterocysts
• Unicellular to filamentous
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