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Biology required practical's - Coggle Diagram
Biology required practical's
Microscopy
preparing a slide to view onion cells
1) add a drop of water to the middle of a clean slide
2) cut up an onion and separate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers.
3) using the tweezers, place the epidermal tissue into the water on the slide
4) add a drop of iodine solution as a stain to add colour to the cell to highlight the features.
5) place a cover slip on top. Try not to get any air bubbles under as they'll obstruct your view of the specimen.
using a light microscope to look at your slide
1) clip the slide you've prepared onto the stage
2) select the lowest-powered objective lens
3) use the coarse adjustment knob to move the stage up to just below the objective lens.
4) look down the eyepiece. Use the coarse adjustment knob to move the stage downwards until the image is roughly in focus.
5) adjust the focus with the fine adjustment knob until you get a clear image of what's on the slide
6) if you need to see the slide with greater magnification, swap to a higher-powered objective lens and refocus.
culturing microorganisms
making an agar plate
1) pour hot jelly into a shallow, round, plastic petri dish
2) when the jelly's cooled and set, inoculating loops (wire loops) can be used to transfer microorganisms to the culture medium.
3) the microorganisms the multiply
testing the action of antibiotics on cultures of bacteria.
1) place paper discs soaked in different types of antibiotics on an agar plate that has an even coating of bacteria. Leave some space between the discs
2) the antibiotics should diffuse into the agar jelly. Antibiotic-resistant bacteria will continue to grow on the agar around the paper discs, but non-resistant strains will die. A clear area will be left where the bacteria have died - this is called the inhabitation zone
3) make sure you use a control. This is a paper disc that has not been soaked in an antibiotic. Instead, soak it in sterile water. You can then be sure that any difference between the growth of the bacteria around the control disc and around the antibiotic discs is due to the effect of the antibiotic alone.
4) leave the plate for 48 hours at 25'C
5) the more effective the antibiotic is against the bacteria, the larger the inhabitation zone will be.
Osmosis
investigating enzymic reactions
Food Tests
measuring the rate of photosynthesis
investigating reaction time
investigating plant growth responses
using quadrats
using transects
investigating decay