25 marksUnfamiliar context3.1.4.2, 3.6.2.1, 3.3.1 and more
Plan for five minutes, then write for about 40. Aim for four or more distinct topic areas, each linked to the title.
The importance of speed and rate in biological processes
Write an essay on this title, drawing on biology from across the course.
[25 marks]
The 45-minute clock starts when you begin typing.
0 words. Breadth and depth score, not length: four linked, detailed areas beat eight thin ones, and an introduction or conclusion earns nothing.
25 marksUnfamiliar context3.1.5.2, 3.2.2, 3.4.2 and more
Plan for five minutes, then write for about 40. Aim for four or more distinct topic areas, each linked to the title.
The importance of accurate copying in living organisms
Write an essay on this title, drawing on biology from across the course.
[25 marks]
The 45-minute clock starts when you begin typing.
0 words. Breadth and depth score, not length: four linked, detailed areas beat eight thin ones, and an introduction or conclusion earns nothing.
9 marksUnfamiliar context3.7.4
A student counted bumblebee visits to eight patches of wild flowers at different distances from a field that had been sprayed with an insecticide. Each patch was watched for one hour on the same afternoon. The patches closest to the field were also beside a busy road. The data are synthetic, written for this question.
Bumblebee visits to eight flower patches (synthetic data)
Distance from the sprayed field / m
Visits per hour
50
3
100
5
200
4
300
9
400
8
600
12
800
11
1000
14
(a)
Calculate Spearman's rank correlation coefficient, rs, for these data. rs=1−n(n2−1)6∑d2
[3 marks]
(b)
The critical value of rs for 8 pairs of data at a probability of 0.05 is 0.738. Interpret your value of rs.
[2 marks]
(c)
The student concluded that the insecticide reduces the number of bumblebee visits. Evaluate this conclusion. Use only information given about this investigation.
A student measured the rate of respiration of yeast with a respirometer at five temperatures, with three repeats at each. From the results, they claimed that yeast respires fastest at 35 °C. The data are synthetic, written for this question.
Rate of oxygen uptake by yeast / mm³ min⁻¹ (synthetic data)
Temperature / °C
Repeat 1
Repeat 2
Repeat 3
15
0.8
0.9
0.8
20
1.4
1.5
1.3
25
2.1
2.4
2.2
30
3.0
3.4
3.1
35
3.3
2.1
3.5
(a)
Calculate the mean rate at 35 °C, excluding any anomalous result.
[2 marks]
(b)
Evaluate the student's claim that yeast respires fastest at 35 °C.
[4 marks]
(c)
Suggest two improvements that would allow the student to find the temperature at which yeast respires fastest.
[2 marks]
Give 2. Extra wrong answers cancel right ones.
(d)
Explain why the rate of respiration increased from 15 °C to 30 °C.
[2 marks]
7 marksUnfamiliar context3.4.4
A population of bacteria grew in a flask. The number of cells was counted every hour and recorded as lg (log to base 10) of the number of cells per cm3. The data are synthetic, written for this question.
Growth of a bacterial population (synthetic data)
Time / h
lg (cells per cm³)
0
3.0
1
4.0
2
5.0
3
6.0
4
7.0
(a)
By what factor did the number of cells per cm3 increase between 0 and 4 hours?
[1 mark]
(b)
Each generation doubles the number of cells. Calculate the number of generations in the 4 hours.
[2 marks]
(c)
Calculate the mean generation time in minutes.
[2 marks]
(d)
Use your answer to (c) to explain why antibiotic resistance can spread quickly through a population of these bacteria.
[2 marks]
6 marksCore biology3.7.4, 3.7.2
A student caught 60 woodlice under logs in a wood, marked each with a small dot of non-toxic paint and released them. Two days later they caught 50 woodlice from the same logs; 12 of them were marked.
(a)
Calculate the estimated number of woodlice in this population.
[2 marks]
(b)
Give two assumptions the student made when using this method.
[2 marks]
Give 2. Extra wrong answers cancel right ones.
(c)
Another student said that because these assumptions were met, the woodlouse population must be in Hardy-Weinberg equilibrium for any gene. Explain why this is wrong.