lab midterm questions Flashcards
objective
contains lenses to magnify the image
Arm
used for a hand grip when carrying the instrument; the other hand should be placed on the base
stage
large, flat surface, supports the slide or specimen over the hole that admits light from below
coarse-focus knob
changes the distance between the objective lens and specimen to permit rough focusing
blue filter
increases resolution by reducing the wavelength of light
mechanical stage
holds slide on stage and allows for exact slide manipulation
mechanical stage knobs
one knob moves a slide vertically, and the other moves it horizontally
fine focus knobs
permits more precise focusing
condenser
contains 2 lenses that focus light onto the specimen
iris diaphragm
regulates the amount of light passing through the lenses in the condenser. reducing the amount of light increases the visibility of semi-transparent objects
condenser adjustment
move the condenser up and down
lamp switch
turns the light on and off
lamp intensity dial
adjusts the intensity of light bulb
stage clips
hold a slide in position over the stage
main switch
controls supply of power to scope. must be in the “on” position for either light to work
T switch
turns the light below a specimen on and off
I switch
turns the light above a specimen on and off
on the light microscope, how is the function of the condenser different from the function of the light source?
the condenser focuses the light on the specimen and light source provides the light
how does the image appear in the dissecting microscope
right side up, moves the same way you move it
how does the image appear in the compound microscope
inverted, upside down and reversed (the left will appear on the right)
where can you find the magnifying power of a microscope lens?
it is indicted on the objectives and eyepieces (4x,8x,40x)
what is the ‘field’?
the bright circle of light you see when you look through the microscope
how do you calculate magnification?
ocular lens x objective lense
how do you calculate the actual size of the specimen?
field diameter x fraction of the field occupied by specimen
when should you never use the coarse adjustment of the compound microscope?
when you are using the highest power objective lens
an organism swims across the high power field(0.4mm) in 16 seconds. how fast is it swimming in um/min?
0.025mm/second so 0.025mm x 60 seconds= 1.5mm/second –>1.5x100um= 150 um/ minute
an object stretches across 1/5 of the low power field (4.5mm). you draw it 6.3cm long. what is the magnification of your drawing?
1/5x 4.5mm= 0.9mm
6.3/0.9mm= 7mm
an object occupies 2/3 of the high power field(0.45mm). you are told to draw it magnified 660x. what will be the length of you drawing?
2/3x0.45= 0.3mm
0.3x 660= 159mm
what are the 5 steps in a scientific method
observation question hypothesis prediction test
what is a hypothesis?
reasonable explanation for observed phenomenon.
can a hypothesis be proven? explain your answer.
no because you would have to prove it in every possible way
what happens if a hypothesis is rejected?
the null hypothesis is accepted
distinguish between the experimental test and control test
the experimental test receives the single variable being tested and the control does not
what is the purpose of the control test?
to minimize the effects of variable other than the independent variable
to compare it to the experimental test
what is the purpose of replicating your tests?
to decrease the likelihood that the observed results are due to chance and increase the likelihood that the results are the response to the environmental conditions
null hypothesis
a statement that the study subjects have no preference for the environmental conditions of the variable you are testing
alternate hypothesis
a statement that suggests that the subjects do have a presence for one environmental condition over another. but does not indicate which environmental choice might be preferred
list 5 abiotic variables that could affect animals in their natural habitat
temperature water/ moisture sunlight wild soil type
difference between compound and dissecting microscope
compound works by letting light pass through the specimen and a sequence of lenses to magnify the image
dissecting used for dissecting specimen, not as powerful as compound
DNA stands for
deoxyribonucleic acid
DNA is a polymer of
nucleotides
Each DNA nucleotide is made of what 3 units?
a five-carbon sugar ring (deoxyribose),
a phosphate group
nitrogenous base
4 Nitrogenous bases in DNA
Guanine
Adenine
Cytosine
Thymine
what are the 2 nitrogenous base groups
Purines - has 2 rings
Pyrimidines - has 1 ring
define phosphodiester bond
nucleotides joined together via bond between the sugar of one nucleotide and the phosphate group of another
positive control
something that will give a positive reaction. (positive control for starch is a starch solution)
negative control
something that will give a negative reaction. (negative control for starch is water)
what is a test for starch and what colour does it turn?
iodine, blue- black colour
what is a reducing sugar test with? what colour does it turn?
Benedict’s, green, yellow, red or brown
test for proteins? what colour does it turn?
Biuret test, violet colour
test for lipids? what colour?
sudan IV, pink or red
Acid Hydrolysis
macromolecules break down into monomers in the presence of heat and acid
distinguish between resolution and magnification
resolution refers to the clarity of an image (distinguishing two objects from one another) , magnification refers to the ability to make small objects seem larger
what is the relationship between magnification and the depth of field?
the higher the magnification the smaller the depth of field
the vertical distance that remains in focus at each magnification is called
depth of field
describe 2 ways to improve the resolution of the light microscope
blue filter improves resolution by reducing the wavelength of light that enters the condenser
resolution can also be improved by adding immersion oil
describe 3 ways to improve contrast of a specimen
adjust the condenser
reducing the amount of light using the iris diaphragm
using artificial dyes
what is contrast
a quality that makes the image stand out better
what is the pH scale used for
a way of describing the concentration of H+ ions in a water solution
