48506933 AS Edexcel Biology Core Practical Summary
CORE BIOLOGY PRACTICALS
You will need to know these practicals as the exam board may ask you questions based on them. Below is a summary of each one.
Name of practical and independent & dependent variables Effect of caffeine on Daphnia heart rate
Independent: caffeine concentration Dependent: heart rate of
Daphnia
Measuring the content of
Vitamin C in fruit juice
Independent: fruit juice
Dependent: volume of juice required to decolourise 1cm3 of
DCPIP
The effect of temperature on cell membranes Independent: temperature of water Dependent: % transmission of light through resulting solution
The effect of changing enzyme concentration on rate of reaction. Independent: concentration of enzyme dependent: time taken for enzyme to break down substrate
Other variables to be controlled
Other equipment
Method and outcome
Temperature
Volume of solutions
Stress of Daphnia
Size of Daphnia
Time of acclimatisation Microscope, counter, cavity slide, dropping pipettes, stop clock, distilled water, test tubes, stop clock
Method: Remove 1 Daphnia and place in cavity slide. Remove pond water and replace with distilled water. Leave for 5mins to acclimatise then observe & count heart rate under microscope for 30s, multiply number by 2 to calculate beats/min.
Repeat with 2 more Daphnia. Repeat again, this time with small concentration of caffeine solution in place of distilled water. Carry out for 5 concentrations of caffeine
= 3 repeats at 3 concentrations.
Outcome: as caffeine concentration increased, heart rate increased
Ensuring Daphnia were same size
If left too long under microscope, temp increases (due to lamp) = increased heart rate
Ensuring enough data is collected
Too high concentration of caffeine kills
Daphnia
Counting of heart beat can be inaccurate
Temperature
Concentration of
DCPIP solution (1%)
Shake each tube same number of times Same end point colour. i.e. until the blue colour of DCPIP just disappears
Volume of distilled water Time left in water
Size of
You will need to know these practicals as the exam board may ask you questions based on them. Below is a summary of each one.
Name of practical and independent & dependent variables Effect of caffeine on Daphnia heart rate
Independent: caffeine concentration Dependent: heart rate of
Daphnia
Measuring the content of
Vitamin C in fruit juice
Independent: fruit juice
Dependent: volume of juice required to decolourise 1cm3 of
DCPIP
The effect of temperature on cell membranes Independent: temperature of water Dependent: % transmission of light through resulting solution
The effect of changing enzyme concentration on rate of reaction. Independent: concentration of enzyme dependent: time taken for enzyme to break down substrate
Other variables to be controlled
Other equipment
Method and outcome
Temperature
Volume of solutions
Stress of Daphnia
Size of Daphnia
Time of acclimatisation Microscope, counter, cavity slide, dropping pipettes, stop clock, distilled water, test tubes, stop clock
Method: Remove 1 Daphnia and place in cavity slide. Remove pond water and replace with distilled water. Leave for 5mins to acclimatise then observe & count heart rate under microscope for 30s, multiply number by 2 to calculate beats/min.
Repeat with 2 more Daphnia. Repeat again, this time with small concentration of caffeine solution in place of distilled water. Carry out for 5 concentrations of caffeine
= 3 repeats at 3 concentrations.
Outcome: as caffeine concentration increased, heart rate increased
Ensuring Daphnia were same size
If left too long under microscope, temp increases (due to lamp) = increased heart rate
Ensuring enough data is collected
Too high concentration of caffeine kills
Daphnia
Counting of heart beat can be inaccurate
Temperature
Concentration of
DCPIP solution (1%)
Shake each tube same number of times Same end point colour. i.e. until the blue colour of DCPIP just disappears
Volume of distilled water Time left in water
Size of