Practical Skills Flashcards
What is an independent variable
This is the characteristic or condition you change intentionally to observe the effect on the dependent variable
What is a dependent variable
This is the phenomenon or condition you aim to observe or measure as a result of the experiment.
What is a controlled variable
This is the condition kept constant to ensure that changes in the dependent variable are due to the manipulation of the independent variable
What is differential staining
This is when multiple stains are used and each stain binds to a specific cell structure, staining each structure differently so the structure can be easily identified
What does acetic orcein do
It binds to DNA and stains chromosomes red
What does eosin do
Eosin stains cytoplasm dark red or pink
What does iodine do
Iodine stains starch blue-black (appears violet under the microscope)
What does iodine in potassium iodide solution do
It stains cellulose yellow
What does haematoxylin do
Stains RNA/DNA a purple/blue colour
What does methylene blue do
It is an all-purpose stain often used to stain DNA blue
How do you mount a wet mount sample
this is used for a variety of live specimens, such as aquatic animals
Use a pipette to put a drop of water on the slide.
Use tweezers to place the specimen in the water.
Put the cover slip on by standing it upright on the slide, next to the water droplet, then carefully tilt it down onto the specimen. Be careful to not add bubbles – these will obstruct the view of the image.
Add a stain. Put a drop on one edge of the cover slip. Put a paper towel on the opposite edge. The paper towel will absorb the stain, drawing it under the coverslip, staining the specimen. (You want to make sure the stain used is not toxic to the live specimen)
How to mount a dry sample
this is used for specimens such as hairs, parts of insects, pollen, parts of flowers etc.
Slice the specimen into a thin piece so light can pass through
Use tweezers to pick it up and put it in the middle of the slide
Put a cover slip on top of it.
How do you calculate the actual length of the species being measured
the number of divisions should be multiplied by the length of one division (you calculated this when you calibrated the graticule).
How do you calibrate a graticule
- Set up the microscope to the required magnification to view the sample.
- Place a stage graticule on the stage.
- Line up the two scales (the stage and eyepiece graticules) similar to the diagram.
- Count the number of divisions on the eyepiece graticule equivalent to each division on the stage micrometre.
- As the length equivalent to each division on the stage micrometer are known, it is possible to calculate the length of one eyepiece division.
What are the rules for drawings
● No shading. Areas that should be shaded should be labelled instead.
● The drawing should take up at least half of the page.
● Label lines must be completely horizontal, drawn with a ruler, exactly touch the object that they’re labelling and must not overlap each other.
● Drawing lines should completely connect and should not be broken
● A scale should be given e.g. for the magnification of the image size.
● They should be drawn in pencil and look like the actual image.
How do you identify the four main vessels attached to the heart during dissection
Identify the four main vessels attached to the heart. Arteries are thick and rubbery, whereas veins are thinner. Identify the coronary artery on the external surface. Locate where the coronary artery connects to the aorta
How do you cut across a stem
You cut the section as perpendicular to the length of the stem as possible and as thinly as possible
What colours does toluidine blue stain tissues
Phloem- red
Xylem- green/blue-green
Sclerenchyma- blue-green/sometimes green
Collenchyma- red-purple
Parenchyma- red-purple
What colour is toluidine blue in non-lignified tissue and lignified tissue
Non-lignified: pink/purple
Lignified: green/blue
When examining a kidney, what is the renal capsule covered in
It is covered in renal capsule
