Practicals

Question 1

Why do you measure to the centre of the spot (RQ7 - chromatography)?

Answer 1

Standardises readings, allows for comparison, it is the mean distance moved by pigment

Question 2

Why would the technique not work as well when using xerophytic plants (RQ7 - chromatography)?

Answer 2

Thick cuticle prevents pigments from being transferred to paper

Question 3

Describe how chromatography could be used to show that chlorophyll is lost in autumn (RQ7)?

Answer 3

Carry out chromatography at different times, find Rf for chlorophyll, look for green substance

Question 4

Why was the leaf midrib not put into the blender and why was a blender used (RQ8 - effect of _ on rate of dehydrogenase activity in chloroplasts)?

Answer 4

No chloroplasts present and too tough to be cut up by blender, breaks open cells to release chloroplasts

Question 5

How did Tube B with no chloroplasts act as a control experiment (RQ8 - effect of _ on rate of dehydrogenase activity in chloroplasts)?

Answer 5

Shows colour change is due to chloroplasts

Question 6

Why were the tubes left in the water bath at 35°C for 5 minutes (RQ9 - effect of _ on rate of respiration)?

Answer 6

Equilibrates temperature

Question 7

Why were the tubes not shaken again (RQ9 - effect of _ on rate of respiration)?

Answer 7

Mixed with O2 which oxidises methylene blue

Question 8

Describe 2 ways in which the maggots used should be similar (RQ10 - effect of _ on animal movement)?

Answer 8

Same age, same species

Question 9

Why was the same maggot not used more than once (RQ10 - effect of _ on animal movement)?

Answer 9

Prevents learning

Question 10

What is one advantage of carrying out repeats (RQ11 - production of dilution series of glucose solution to identify conc. of glucose in urine sample)?

Answer 10

Calculate reliable mean

Question 11

How would you randomly sample an area to estimate population size (RQ12)?

Answer 11

1. Use a grid
2. Obtain coordinates using random number generator
3. Count number of _ in quadrat
4. Calculate running mean
5. Multiply running mean by total no. of quadrats (large number)

Question 12

How would you use a transect to investigate how species distribution changes over an area (RQ12)?

Answer 12

1. Lay tape and take samples at regular intervals (quadrat)
2. Count % cover in each quadrat
3. Use multiple transects so representative and take mean at each distance along transect