RPs Flashcards
Microscopy
Method:
1) Collect a sample of the cell you wish to observe
2) Remove the inner skin of a layer of onion using forceps, or a thin layer of algae using a scalpel
3) Place the thin slice onto a clean glass slide. Use forceps to keep cell the on the glass slide
4) Using a pipette, add one or t wo drops of dilute iodine solution on tep of cell
6) Lower the coverslip slowly so that liquid spreads out
5) Hold the coverslip by its side and lay one edge onto slide near the specimen
Culturing Bacteria
Method:
Sterilize agar plates and inoculating loop by passing it through a flame.
Streak bacteria onto agar; tape lid(not fully seal, still need oxygen); store upside down to stop condensation; incubate at 25°C for school safety.
Can vary experiment by adding different antibiotics and antiseptics and testing the effectiveness
Required practical - the effect of osmosis on plant tissue
Aims of the experiment
To investigate the effect of a range of
sucrose solutions, on the mass of potato cylinders. Concentration is measured in moles. A 1.0 mol dm-3 solution of a substance contains
one mole of the substance per dm-3 of a solution, or one mole per litre of solution.
Method:
Set up 6 boiling tubes, each containing the same volume of one of the sucrose solutions. The 0.0 mol/dm-3 sucrose solution is distilled water. Label the boiling tubes.
Prepare 6 potato cylinders using a borer and cut the cylinders to the same length. Gently dry each potato cylinder using a paper towel to remove excess liquid and record its mass before placing it into one of the boiling tubes.
Leave the potato cylinders in the boiling tubes for 40 minutes.
Remove each potato cylinder from its boiling tube, gently remove excess liquid from the surface of the cylinder with a paper towel and record its mass.
If possible, repeat the experiment to obtain multiple values of mass change for each solution. Making a series of repeat measurements will enable you to identify and ignore any anomalous results and to calculate a mean.
Independent Variable: The concentration of the sucrose solutions, with a range of 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 mol/dm-3.
Dependent variable: The change in mass of the potato cylinders.
Control variables: The time that each cylinder is left in the sucrose solution, the size of each cylinder.
Food Tests:
Method:
Starch: Iodine → blue-black.
Sugar: Benedict’s → brick red.
Protein: Biuret → purple.
Fat: Ethanol → white emulsion.
Enzyme Activity (Amylase & Starch)
Add iodine to spotting tile
Mix 2cm3 amylase, starch, and 1cm3 pH buffer.
Start Stopwatch
Test by adding solution to iodine in spotting tile every 10 seconds until no color change.
Repeat using different pHs
Photosynthesis
Method:
Place pondweed in a beaker of water with sodium hydrogencarbonate (NaHCO₃).
Shine a lamp at a fixed distance and count oxygen bubbles produced in 3 minutes.
Measure bubble volume using a gas syringe or ruler.
Repeat at different light distances.
Variables:
Independent: Light distance (or intensity).
Dependent: Oxygen production (bubble count/volume).
Control: Temperature, NaHCO₃ concentration, pondweed mass.
Reaction Times
Ruler drop test
Work with a partner.
Person A holds out their hand with a gap between their thumb and first finger.
Person B holds the ruler with the zero at the top of person A’s thumb.
Person B drops the ruler without telling Person A and they must catch it.
The number level with the top of person A’s thumb is recorded in a suitable table. Repeat this five times.
Swap places, and record another five attempts.
Variables:
Independent: Participant (or distractions).
Dependent: Reaction time.
Plant Responses/Phototropism
Method:
Put cotton wool into three petri dishes,
Add ten seeds to each dish and place them in a warm place where they won’t be disturbed.
Allow the seeds to germinate, and add more water if the cotton wool dries out.
Once the seeds have germinated, ensure the petri dishes each contain the same number of seeds, and remove any extra seeds if necessary.
One petri dish will sit in full light on a windowsill, the second will be in a dark cupboard, and the final dish will be placed in partial light.
Every day for one week, measure the height of each seedling and record the results in a table.
You must record the height of the individual seedlings on each day.
Calculate the mean of the seedlings each day, and compare the mean heights in the three different locations.
Variables:
Independent: Light condition.
Dependent: Shoot length.
Controls: Temperature, volume of water given, number of seeds on each dish
Transects and Quadrats sampling
Method:
Random Sampling:
Use random coordinates to place a quadrat 10 times.
Count target species (e.g., dandelions) in each quadrat.
Estimate total population using
Population=Total area/Sampled area ×Total counted
Transect Sampling:
Lay a tape measure against ecological gradient(change in abiotic factor such as light intensity, soil humidity and soil pH)
Place quadrats at 0 m, 5 m, 10 m; count mean species.
Plot a graph of abundance vs. ecological gradient
Decay (Milk pH Change)
Add 20 cm³ fresh milk to 3 beakers.
Incubate at different temperatures (e.g., 20°C, 30°C, 40°C).
Measure pH daily for 3 days using indicator paper or a pH meter.
Compare rates of pH drop (due to bacteria converting lactose sugar in the milk to lactic acid and fat digestion into fatty acids)
Independent: Temperature.
Dependent: pH change.
Control: Milk volume, initial pH, time intervals, type of milk
