Biology practical skills

Give the method for RP 1 microscopy (measuring the size of cells)

1. Place the sample on a slide with a drop of water/stain and place a cover slip at an angle to avoid air bubbles

2. Use the lowest magnification objective lens first to locate the sample

3. Adjust the focus with the coarse and dune focus knobs

4. Use an eyepiece graticule to calibrate measurements

5. Calculate actual size using:

6. Actual size= image size/magnification

Give the method for RP 2 preparing a root tip squash (mitosis)

1. Cut 1-2cm of a root tip

2. Place in HCl at 60°C for 5 minutes to break down cell walls

3. Rinse in distilled water and place on a slide

4. Stain with toluidine blue or acetic ore in to highlight chromosomes

5. Use a mounted needle to spread the root tip and squash with a coverslip avoiding sideways movement

6. Examine under a microscope and count cells in each mitotic stage

Give the method for RP3 investigating water potential in plant tissues

1. Cut equal sized potato cylinders and blot dry

2. Weigh each before placing them in different concentrations of sucrose solution

3. Leave for at least 20 minutes

4. blot dry and re weigh

5. Calculate the % change in mass using: (final mass -initial mass)/initial mass x100

6. Plot a graph of % change in mass against sucrose concentration to estimate water potential

Give the method for RP4 investigating membrane permeability

1. Use a cork border to cut beetroot cylinders equally

2. Rinse to removes excess pigment

3. Place in a test tube with water at different temperatures

4. Leave for 10 minutes

5. Use a colorimeter to measure absorbance of the solution

6. Higher absorbanve = more pigment released = greater membrane permeability

Give the method for RP5 the effect of enzyme concentration on a rate of reaction

1. Prepare different enzyme concentrations using serial dilution

2. Add enzymes to substrate in a test tube

3. Use a stopwatch to record time taken for a visible change

4. Repeat at least 3 times and calculate a mean

5. Control temperature using a water bath

Give the method for RP6 investigating the rate of photosynthesis

1. Place pondweed in a test tube of sodium hydrogen carbonate solution

2. Place a light source at a set distance

3. Leave to acclimate for 5 minutes

4. Count oxygen bubbles produced per minute or collect oxygen using a capillary tube and measure the volume

5. Repeat with different light intensities

Give the method for RP7 chromatography of photosynthetic pigments

1. Grind the leaf sample with propanone

2. Use a capillary tube to place a concentrated spot of pigment onto chromatography paper

3. Place in a beaker with solvent

4. Allow the solvent to rise up the paper

5. Calculate the Rf value

6. Rf= distance moved by pigment/distance moved by solvent

Give the method for RP8 investigation of the rate of respiration in yeast

1. Place yeast and glucose solution in a sealed test tube

2. Connect to a respirometer with a drop or coloured liquid in the capillary tube

3. Leave in a water bath at a controlled temp

4. Measure the movement of lieuqid over time

5. Use rate=distance moved by liquid/time

6. Repeat at different temps to compare

Give the method for RP9 investigating the effect of a named growth factor in bacteria growth

1. Pour sterile nutrient agar into Petri dishes

2. Use a sterile pipette to spread bacteria culture evenly

3. Place paper discs soaked in different antibiotics onto the agar

4. Seal the petri dish with tape and incubate at 25°C

5. Measure the clear zone around each disc

Give the method for RP10 investigating the effect of an abiotic factor on organism distribution

1. Use a random sampling method

2. Place a quadrat and count the number of organisms inside

3. Repeat multiple times for reliability

4. Use a transect for systematic sampling along and environmental gradient

5. Calculate mean density or percentage cover