All Required Practicals Paper 2

Question 1

How to measure reaction time

Answer 1

1) Sit with arm resting on the edge of the table.
2) Hold ruler vertically between thumb and forefinger level with 0. Let go without any warning.
3) The person being tested should catch the ruler as quick as possible.
4) The number on the top of the thumb and forefinger shows reaction time.
5) Repeat several times and find mean.

Question 2

How to use quadrats to find distribution of organisms.

Answer 2

1) Place a 1 m2 quadrat on the ground at a random point within the first sample area.
2) Count the organisms within the quadrat
3) Repeat as many times as possible.
4) Work out mean number of organisms per quadrat with first sample area
5) Repeat experiment in different sample areas and compare the means

Question 3

How to use transects to study distribution along a line

Answer 3

1) Mark out a line in the studied area using a tape measure.
2) Count all the organisms you’re interested along the line, or put quadrats along the line and count the number of organisms you’re interested in.

Question 4

How to investigate the effect of temperature on rate of decay

Answer 4

1) Add 5 cm3 of lipase solution to a test tube, label L
2) Add 5 cm3 of milk to a different test tube, label M
3) Add 5 drops of phenolphthalein indicator to the test tube containing milk and add 7 cm3 of sodium carbonate solution to make it alkaline. It should turn pink.
4) Put both tubes into a water bath until they reach 30 degrees C.
5) Use a calibrating pipette to put 1 cm3 of the lipase solution into the milk and start stopwatch.
6) Stir the contents of the tube with a glass rod, the enzyme will start to decompose the milk.
7) As soon as the solution loses its pink colour, stop the stopwatch and record the time taken. Repeat 3 times and find mean.
8) Repeat the whole experiment at different temperatures to compare how temperature affects the rate.