PAGs Flashcards
How do you measure the length of a specimen using a microscope?
Place a stage micrometer on the stage at the magnification the sample will be viewed
Align the scale of the eyepiece graticule with the stage micrometer
Count the number of divisions on the eyepiece graticule that is equivalent to the stage micrometer, work out the length that each EPU represents (1 division on the stage micrometer =10 micrometers)
Place the sample on the stage at the same magnification and measure the length with the eyepiece graticule
Use the conversion factor to measure the real life length
How do you prepare a sample for a light microscope?
Slice very thinly with a sharp blade so as much light can pass through as possible
Ideally use a wet mount to decrease distortion of the tissues
Including using a stain, adding to the edge and blotting paper to remove excess
Cover slip at an angle, reduce risk of bubbles
Or dry mount, thinnest and cover slip with parallel
How do you use a light microscope?
Clip the slide on the stage
Use the lowest powered objective lens, and use coarse focus then fine focus, but moving the lens away from the slide (prevent breaking)
Measure length using eyepiece graticule and scale with calculations
What are the features of biological drawings?
ATLEAST HALF THE SPACE
No shading, cross hatching
Label lines horizontal, must not overlap
Drawing lines connect, no ends
Scale, Magnification
Use a sharp pencil
Title
How do you dissect a heart?
First identify the different chambers of the heart via the thickness, and main vessels
Using a clean sharp scalpel, cut along the sides of the heart, use scissors to cut through the ventricles
Examine the inside, valves
Measure thickness
What are precautions/ safety for dissections?
Sharp, sterile equipment
Place equipment into a sterile solution after use, sharp ends downs
All biological waste in separate bags
Cut away from you
How do you dissect a plant?
Use a scalpel to cut a cross-section of the stem
Then from this cross sections, cut very thin perpendicular sections, this is a transverse section
Place in water, then stain, rinse of excess, on slide
View under microscope
Can repeat with longitudinal if you want
How do you sample an area randomly?
Set up an X and Y axis across the length
Use a random number generator to generate the coordinates, and place the bottom right of the quadrat at the coordinates
Take a note of the percentage cover of species- quadrat divided into 100, number of squares species occupy at least 50% of is percentage cover, scale up by the number of quadrats that can fit in the area
How do you dissect a fish?
Observe, model movement of water, bones
Using scissors, remove the operculum to show the gills and gill arch
Cut a section of the gill arch off using scissors
Observe under a microscope
How do you use a colorimeter?
Select the colour complimentary to the colour of the solution e.g red for blue Benedict’s
Set the colorimeter to 0 with distilled, with light able to pass through the clear sides of the cuvette
Make standard solutions of different concentrations of the solution being tested, and measure the absorbance of the light
Plot a calibration curve
Carry out the experiment and measure absorbance of the solution
Compare to concentration with the curve
How do you use a potometer?
Cut shoot underwater to prevent air entering the xylem
Assemble the potometer in water, and insert the shoot underwater to prevent air entering
Remove the apparatus from the water but keep the end of the capillary tube under water
Use petroleum jelly to seal the shoot at the joint, check equipment water tight and without air
Dry the leaves
Allow the plant to climatise
Add in one air bubble via lifting the capillary tube up out the water and putting it back in
Position the air bubble to the end of the marked section using the reservoir
Carry out the experiment and record how much the bubble moves in a certain time
What are limitations of measuring transpiration using a potometer?
Measures water uptake not water loss
Some water taken in not for transpiration, but enters cells e.g turgidity
Reactant in photosynthesis
Plant dying when roots cut off, may affect water uptake
How do you use gel electrophoresis?
DNA cut via restriction enzymes
Add agarose gel to the gel tray, sets, forms wells, into tank
Wells must be closest to negative electrode
Add buffer solution
Add DNA and loading dye using a micropipette- dye helps DNA fragments sink to bottom of well, fragments more visible
Put lid on gel box, turn on power
DNA fragments are negatively charged, so repelled by the cathode. Smaller DNA fragments move more quickly
Let run till dye 2cm from the end
Turn off, add stain, Southern blotting with nylon, compare bands
What sterile techniques are used when working with bacteria?
Wash hand and disinfect area
Have a bunsen burner near by so no pathogens from the air fall in
Flame neck of bottle of broth to prevent microorganisms in the air entering
Only open the petri dish enough to enable the correct bacteria to enter
Sterilise all equipment in ethanol/flaming in the Bunsen, and then after sterilised and placed in disinfectant
How do you use a spirometer?
Persons breathes through a tube connected to an oxygen chamber
As the person breathes in and out, lid moves up and down
Breathing in oxygen out carbon dioxide, but Ca(OH)2 limewater to remove any carbon dioxide
Means net volume in the machine decreases, so volume moves down to show oxygen uptake
Nose clip and machine must be air tight for accurate readings
