Biology Required Practicals

1-Cut open an Onion

2-Use forceps to peel a thin layer of epidermis from the inside

3-Lay the layer onto a glass microscope slide

4-Add a drop of iodine solution to the layer

5-Carefully place a cover slip over the layer 

(Gently, with forceps, so that you don't get air bubbles)

6-Examine the slide over the layer

(Adjust Objective lenses and stage for best view)

7-Draw what you can see

1-Prepare a range of sugar (sucrose) solutions. Range from 0.2 mol dm^-3 to 1.0mol dm^-3.

2-Set up a range of boiling tubes with each of these solutions, include one containing distilled water (0.0mol dm^-3) to act as the control variable.

3-Lable each tube with the conentration it is.

4-Prepare a results table, weigh the food source. Each sample should weigh the same and come from the same source. (Possible to record different weights- but do not get each weight mixed up)

5-Measure the mass of the sample in each solution before and after to show the rate of osmosis, Be sure to gently dry each piece to get rid of excess solution.

Note: Osmosis is the movement of water particles. Water can move in and out of a source depending upon the concentration. The food source can lose or gain weight, depending on the flow of osmosis. 

1-Investigate the breakdown of starch by amylase at different pHs.

2-Different pH produced with a buffer solution - they produce specific pHs and maintain that pH if other substaces are added.

3-Amylase breaks down the starch

4- Set up a series of test tubes with a mix of starch and amylase at different pHs

5-Use a pipete to remove a sample every 10seconds to test for starch, Iodine turns blue/black when starch is present. If there is not starch present the solution remains orange/brown

6-For each pH record  the time taken for the complete dissaperance of starch

Note: Keep each sample into the well of a spotting tile when you test for starch, stop when the iodine solution doesn't change colour.

A1- Reducing sugars (Like glucose) give a red/brown precipitate with Benedicts solution

A2-You need to heat the substance with Benedicts solution and then wait for the reaction 

A3-If there isn't much glucose present it turns Green, yellow or orange (if there is a little more).

B1-Crush sample so it can dissolve, filter/dilute it with ethanol to get a clear liquid to get a solution of fat and ethanol at the end of filterisation

B2- Add the ethanol/fat mixture to test tube of water, a white emulsion indicates fats/oils are present.

1-Set up a boiling tube with 25cm^3 of sodium hydrocarbonate solution, allow tube to stand for a few minutes and shake to dispose of any air bubbles that may form

2-Cut a piece of pondweed 8cm long

3-Use forceps to place it into the boiling tube- don't damage the pondweed or overflow the water

4-Position the tube 10cm away from the light source, leave to stand for a few minutes, count bubbles produced from cut end of pondweed in one minute 

5-Repeat the count several times and record the results

6-Calculate average number of bubbles produced per minute

7- Repeat these steps at different distances from the light source.

1-Person A holds out their hand with a gap between their thumb and first finger

2-Person B holds the ruler with the 0 at the top of Person A's thumb

3-Person B drops the ruler without warning and Person A must catch it

4-The number at the top of Person A's thumb is recorded- Repeat these steps several times

5-Swap places and record another several times

6-Record the catch is cm to work out reaction time.

1-Chose a starting point on a field, where grass is often cut

2-Use random numbers to generate a set of coordinates to place the first quadrat 

3-Count number of plant species within this quadrat

4-Return to the starting position and repeat steps 2 and 3 multiple times (10ish), using more random coordinates 

5-Repeat 1-4 for a part of the field where the grass is not often cut 

6-Compare your results by calculating the mean for each location.