Biology Unit 2 Core Practicals

1) Cut a 5mm long tip from a growing root.

2) Place the root tip on a watch glass and add a few drops of hydrochloric acid.

3) Add a few drops of stain (e.g. toluidine blue) so that the chromosomes become darker and easier to see under a microscope.

4) Warm the watch glass (but don't boil the liquid) by passing it slowly through a bunsen burner flame.

5) Place the root tip on a microscope slide and use a mounted needle to break it open and spread the cells out thinly.

6) Add a few more drops of stain and then place a cover slip over it.

7) Squash the cover slip down gently

8) Warm the slide again for a few seconds to intensify the stain.

9) The cells are now ready for observation.

1) Attach the fibre to a clamp stand and hang a weight from the other end.

2) Keep adding weights, one at a time, until the fibre breaks.

3) Record the mass needed to break the fibre- the higher the mass, the higher the tensile strength

4) Repeat the experiment with different samples of the same fibre to increase reliability

5) The fibres being tested should always be the same length.

6) Other variables such as temperature and humidity should remain constant throughout.

7)  Safety measures also need to be taken into account, such as wearing eye goggles and standing away from the weights.

1) To take extracts from the desired plant: dry and grind each plant, and then soak them in ethanol. (ethanol acts as a solvent). The plants should all be the same size, so the amount of extract is the same.

2) Filter off the liquid (the ethanol containing the dissolved plant extract).

3) Evenly spread a sample of bacteria onto an agar plate.

4) Dip discs of absorbant paper in each extract. The discs should all be the same size so that they absorb the same volume of liquid.

5) Also make a control disc, which has been soaked in ethanol.

6) Place the paper discs on the agar plate- they must be spread out.

7) Incubate the bacteria to allow the bacteria to grow.

8) Where the bacteria can't grow- a clear patch will form called an incubation zone.

9) The size of the incubation zone tells you how well the antimicrobial plant is extract is working.

1) A single cell is taken from a growing area on a plant (e.g. root or shoot)

2) The cell is placed in some growth medium (e.g. agar) that contains. The growth medium is sterile, so microorganisms can't grow and compete with the plant cells.

3) The plant will grow and divide into a mass of unspecialised cells. If the conditions are suitable, the unspecialised cells will differentiate into specialised cells.

4) Eventually, the cells will grow and differentiate into an entire plant.

Tissue culture shows totipotency because a single stem cell can produce all the specialised cells to make a whole plant.

Method: (Using CALCIUM ION DEFICIENCY AS EXAMPLE)

1) Take 30 seedlings of the same plant (they should be the same age and height) and plant them in seperate pots.

2) Make up 3 nutrient broths containing all the essential minerals, but vary the concentration of calcium ions. Make up one broth with a high concentration, one with a medium concentration, and one with a low concentration of calcium.

3) Split the plants into 3 groups. Each group should be given only 1 broth.

4) Record the heights of the plants after 7 weeks. Calculate the average height for each group of plants.

5) During the experiment it's important to keep all other variables the same, e.g. the amount of sunlight and water the plants receive.