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1.
The effect of population density on aggressive behaviour was studied in three groups of
chimpanzees. Group I lived in a crowded space and were able to hear their neighbours. Group II
lived in a crowded space, unable to hear their neighbours, and Group III lived in a large, isolated
compound. The level of aggression was measured according to the average number of fights per
day. Fecal matter was collected and analysed for the level of cortisol. (When anxious or stressed,
chimpanzees produce more cortisol.) The bar charts summarize the results obtained.
4
Level of
3.5
aggression /
fights day –1 3
2.5
2
1.5
1
0.5
0
Cortisol /
ng g –1
of fecal
matter
Aggression
Group I
Group II
Group III
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Anxiety
Group I
Group II
Group III
[Source: Frans B M de Waal, et al., (May 2000) Scientific American, pages 54-59]
(a)
Identify the level of cortisol in Group III.
.....................................................................................................................................
(1)
(b)
Compare the difference in aggressive behaviour between Groups I and II.
.....................................................................................................................................
(1)
(c)
Outline the effects of living conditions on stress using the data above.
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(2)
1
(d)
One hypothesis suggests that stress leads to more aggressive behaviour. Evaluate whether
the data supports this hypothesis.
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(3)
(Total 7 marks)
2.
To move in the correct direction, wandering spiders (Cupiennius salei) depend on slit sense
organs in their exoskeletons. In an experiment to show the importance of these organs, two groups
of 32 spiders were used. One group had their slit sense organs intact and the other group had them
temporarily damaged. Both groups were temporarily blinded so that so they could not see where
they were going.
The spiders were briefly presented with a housefly which was then removed. The spiders were
placed in the centre of a grid and the starting angle that each spider took to find the housefly again
was recorded, with 0° leading directly to the housefly and 180° being in the opposite direction to
the housefly.
Spiders with intact
slit sense organs
F
0º
270º
F
270º
90º
S
Spiders with damaged
slit sense organs
F
0º
S
F
90º
30 cm
180º
180º
Starting angle
Starting angle
S
Key:
S = starting point of the spider
S
F = position of the housefly
[Source: Modified from S Zill and E Seyfarth, Scientific American (July 1996), pages 70–74]
(a)
Calculate the percentage of spiders that walked with a starting angle within 30° in either
direction of the housefly in the two groups of spiders.
2
(i)
Spiders with intact slit sense organs. ..............................................................
...........................................................................................................................
(1)
(ii)
Spiders with damaged slit sense organs: ........................................................
...........................................................................................................................
(1)
(b)
Compare the effect of damaging the sensors in the two groups of spiders.
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.....................................................................................................................................
.....................................................................................................................................
(2)
(c)
Discuss whether the spiders were showing innate or learned behaviour in this experiment.
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(3)
(Total 7 marks)
3
3.
Two groups of 15 rats were trained to escape from an electric shock that was applied to one
compartment of their cages. For one group (labelled EscD) the shock coincided with switching
off the light, resulting in darkness in that compartment. The training was repeated for five
sessions. The graphs below show the mean results for the two groups.
Group Esc
Group EscD
3.0
3.0
2.5
2.5
2.0
2.0
Escape 1.5
times / s
1.0
1.5
0.5
0.5
1.0
0.0
0.0
1
2
3
Session
4
5
1
2
3
Session
4
5
[Source: K. Zielinski and Savonenko, (2000), Acta Neurobiol. Exp, 60, pages 457-465]
(a)
(i)
Calculate the difference in escape times in session 1 between the two groups.
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
Suggest a reason for the difference.
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...........................................................................................................................
(1)
(b)
(i)
Compare the changes in escape times over the five sessions between the two groups.
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...........................................................................................................................
...........................................................................................................................
(2)
(ii)
Deduce, giving a reason, which group shows more evidence of learned behaviour.
...........................................................................................................................
4
...........................................................................................................................
(1)
(c)
If the researchers were to continue their experiments with the group Esc and apply the same
experimental conditions as for the group EscD, predict what would happen to the escape
times for the group Esc.
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 6 marks)
4.
The antennae of the American cockroach (Periplaneta americana) are very sensitive to touch.
Tapping an antenna causes a quick turning and running response.
The figures below summarize the results of touch trials. The cockroach in Figure A is shown by a
symbol in the centre to indicate orientation; the circle represents its head. The cockroach was
tapped on one of its antennae and the path of the cockroach’s movement was plotted.
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The circular histogram in Figure B shows the initial angle of turn for cockroaches tapped on the
left antenna. The arrow points to the mean angle of turn. Figure C shows the response time (the
time between touch and actual movement) for 215 trials.
[Source: Ye and Comer, Journal of Neuroscience, (1996), 16, pages 5844–5853; 1996 by the Society for Neuroscience]
(a)
(i)
State the mean angle of turn.
...........................................................................................................................
(1)
The circular histogram in Figure B can be divided into four 90° quadrants, starting at 0°.
(ii)
Identify the quadrant which scored the lowest number of cockroach runs.
...........................................................................................................................
(1)
6
(b)
(i)
State the response time with the greatest frequency.
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(1)
(ii)
State the range of response times.
...........................................................................................................................
(1)
(iii)
Suggest one reason for the variation in response time.
...........................................................................................................................
...........................................................................................................................
(1)
(c)
Using Figure A, deduce, giving a reason, which antenna was tapped.
.....................................................................................................................................
(1)
(d)
Discuss the survival value of the behaviour of cockroaches demonstrated by this
investigation.
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(2)
(Total 8 marks)
7
5.
Colouration is an important adaptive trait that can protect an organism from predators. Behaviour
and colour change were studied in two larval amphibian species. Ambystoma barbouri is found in
streams containing the predatory sunfish. A. texanum is found in temporary ponds and streams
which lack the predator.
A. barbouri larvae are significantly darker than A. texanum larvae. This contrasts with the natural
habitats of the species as A. barbouri is typically found in areas with light substrate and A.
texanum live in ponds with dark substrate.
Experiments were performed to measure the amount of behavioural colour change due to
predation risk. Larvae were initially kept on a dark or light background and then switched to the
opposite background in the presence and absence of predator chemical cues (CC) which simulate
the presence of a predator. The graphs below show the change from initial to final colour. Higher
values indicate a lighter colour.
[Source: T S Garcia and A Sih, Oecologia, (2003), 137, pages 131139]
8
(a)
Identify the colouration treatment and species in which the greatest colour change was
observed when the larvae were in the presence of chemical cues.
....................................................................................................................................
....................................................................................................................................
(1)
(b)
State the relationship between the background colour and the initial colour of the larvae.
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....................................................................................................................................
(1)
(c)
Outline the effect of predator chemical cues (CC) on colour change when the larvae are
initially on a dark background.
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(2)
(d)
Suggest one behaviour that the larvae could use to avoid predation.
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....................................................................................................................................
(1)
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(e)
Research has indicated that A. barbouri evolved from A. texanum over 10 000 years ago
when it moved from ponds into streams. Discuss how natural selection may have affected
the colour change behaviour.
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....................................................................................................................................
(2)
(Total 7 marks)
10