1.	(a)	in flight	1
 
(b)	;
4.2 (%); (Allow answers from 4% to 4.2%)	1 max
 
(c)	birds spend most of time active on the water;
more or less the same time in flight, diving and resting in water;
Need all three parts for the mark.	2
 
(d)	birds need to rest/sleep to recover energy/digest food / are inactive
at night;
moulting makes them flightless;
defending territory / protection of young / other example of social
behaviour;	2 max
[6]

2.	(a)	166 mg m^–2 (Allow answers in the range of 162–168 mg m^–2)	1
 
(b)	rapid rise and fall between April and August;
peak in May/June;
fluctuates between August/September and December;
low December/January until February/March;
cyclical;	2 max
 
(c)	negative relationship / during period of defoliation, biomass
(of terrestrial invertebrates) is at its lowest;
less leaves means less food/habitats / easier for predators to
see invertebrates;
defoliation occurs in winter/autumn and the cold may kill
invertebrates;	2 max
 
(d)	(aquatic invertebrate flux) decreases because movement to the
forest has occurred (by adult forms) / fewer aquatic invertebrates
left in the stream so fewer are moving;
fluctuation due to movement of different species/different life
cycles/second generation;
decreases because invertebrates left at the beginning of
winter/cold season;
(adult forms) move to utilize (changes in) food supply in forest;	2 max
[7]

3.	(a)	15 days	1
 
(b)	13 – 9 = 4(days) or  × 100 or 100 – 69.2;
31% or 30.8% or 30.77%;	2
 
(c)	both types of sound decreased mean time to egg laying;
extra-colony sound decreased time more than intra-colony;
both types of sound increased (mean) number of eggs laid;
same (increase in) egg number with intra- and extra-colony sound;
no information on sample sizes/number of pairs/egg size;
competition (implied/perceived) leads to earlier egg laying;	3 max
Answers must evaluate the effect of the sounds, not merely
compare the results.
[6]

4.	(a)	downwind approach distance increases with increasing nest-feeder
distances / the closer the feeder to the nest, the shorter the downwind
approach distance / direct/positive relationship	1
 
(b)	feeders at 5 m have smaller downwind approach distances than
feeder at 60 m / vice versa;
feeder at 5 m has peak frequency at 50% whereas at 60 m peak/
plateau/flat at 20%;
narrower range of approach distances for 5 m while wider range of
approach distances for 60 m;
feeders at 5 m has peak approach distance at 1 m downwind while
feeders at 60 m has peak plateau at 4 m–4.5 m;	3 max
 
(c)	difficulty handling ants / size of ants;
variation of wind;
other odours;
path of trail not easy to measure accurately;
Accept any other reasonable suggestions.	1 max
 
(d)	EITHER:
innate behaviour/taxis;
because all walking at same angle to constant wind/all turn and follow
odour trail when they detect smell;
OR:
learned behaviour;
may have learned because of repetition/training/following other ants;	2
[7]

5.	(a)	downwind approach distance increases with increasing nest-feeder
distances / the closer the feeder to the nest the shorter the downwind
approach distance /
direct/positive relationship	1
 
(b)	feeder at 5 m has smaller downwind approach distances than feeder at
60 m / vice versa;
feeder at 5 m has peak frequency at 50% whereas at 60 m peak/plateau
at 20%;
narrower range of approach distances for 5 m while wider range of
approach distances for 60 m;
feeder at 5 m has peak approach distance at 1 m downwind while feeder
at 60 m has peak/plateau 4 m–4.5 m;	3 max
 
(c)	difficulty handling ants / size of ants;
variation of wind;
other odours;
path of trail not easy to measure accurately;
Accept any other reasonable suggestions.	1 max
 
(d)	EITHER
innate behaviour / taxis;
because all walking at same angle to constant wind / all turn and follow
odour trail when they detect smell;
OR
learned behaviour;
because of repetition/training / following other ants;	2
[7]

6.	(a)	 × 100 = 160% (units required)	1
 
(b)	bees with previous exposure/experimental group fly around the source
more than the control group;
bees with previous exposure/experimental group fly towards the source
more than the control group;
bees with previous exposure/experimental group circle more than the
control group;
in bees with previous exposure, orientated flight is greater than circling;
Accept vice versa statements.	2 max
 
(c)	the bees associate the odour with food, and this is learned/conditioning
behaviour
Do not accept taxis or simply learned behaviour or conditioning.	1

(d)	previous exposure leads bees to fly to food source more directly;
giving them an advantage in finding food;
increasing their chance of survival;
and passing their genes to the next generation;
less energy expended finding food;
more direct flight/less flight time reduces chance of predation;	3 max
[4]

7.	(a)	bees with previous exposure/experimental group fly around the
source more than the control group;
bees with previous exposure/experimental group fly towards
the source more than the control group;
bees with previous exposure/experimental group circle more than
the control group;
in bees with previous exposure, orientated flight is greater than circling;
Accept vice versa statements.	2 max
 
(b)	the bees associate the odour with food, and this is learned/
conditioning behaviour
Do not accept taxis or simply learned behaviour or conditioning.	1
 
(c)	previous exposure leads bees to fly to food source more directly;
giving them an advantage in finding food;
increasing their chance of survival;
and passing their genes to the next generation;
less energy expended finding food;
more direct flight/less flight time reduces chance of predation;	3 max
[6]

8.	(a)	(i)	(mean) chick mass increases in presence of helpers	1
 
(ii)	female survival probability increases in presence of helpers	1
 
(b)	 × 100% or other correct calculation;
5.8%;
Accept the correct answer if it is not rounded up to 5.8% or if it
is rounded up to 6%.	2

(c)	with helper, smaller egg volume;
less resources from mother to produce egg/rear young;
more resources toward survival of mother;	2 max
[6]

9.	(a)
Rods | Cones
work better in dim conditions | only stimulated by bright light;
absorb all the visible wavelengths of light / but do not distinguish wavelengths/colours | different kinds of cones absorb different wavelengths / different types for different wavelengths/colours of light;
spread through retina | concentrated in centre of retina;
multiple rod cells per neuron | one cone cell per neuron;
		3 max
 
(b)	receptors detect stimuli;
transmit information regarding stimuli to the central nervous system;
via sensory neurons;
central nervous system sends impulse to effector;
via motor neuron;	3 max
 
(c)	Award [1] for every two correct answers.
thermoreceptor / chemoreceptor / photoreceptor / mechanoreceptor /
baroreceptor / propioceptor	2 max
[8]

10.	(a)	a conditioned response is learned whereas an unconditioned
response is innate;
an unconditioned response is made to an unconditioned
stimulus whereas a conditioned response is made to a
conditioned stimulus;	2
 
(b)	binds to cannaboid/pre-synaptic receptors;
inhibits neurotransmitter release;
therefore no excitation of post-synaptic membranes;	2 max
[4]

11.	(a)	sensory neurons receive information from receptors;
transmit nervous impulses to the central nervous system;
relay neurons in the central nervous system transmit the information
from sensory neurons to motor neurons;
motor neurons send impulse to effector;	3 max
 
(b)	taxis is (directional) movement towards/away from a stimulus whereas
kinesis is more movement in unfavourable conditions and less movement
in favourable conditions;
example;	(e.g. Planaria moving towards food / Euglena moving towards
	light is taxis and woodlice moving more in (unfavourable) dry
	conditions is kinesis)	2
 
(c)	inhibition of nervous impulses / binding to cannabinoid receptors / blocking
of release of excitatory neurotransmitter	1
[6]

12.	(a)	(i)	dark	1
(ii)	because they are nocturnal / avoid predation by being active at night	1
 
(b)	group A is able to maintain a rhythm while group B is not;
group B is active more frequently than group A;
group B is active for a shorter period than group A;	3
 
(c)	(before constant darkness) group B had a rhythm suggesting cytochromes are
not necessary;
	(after constant darkness) group B were unable to re-establish a rhythm
suggesting cytochromes are necessary;
cytochromes involved along with other variables;	2 max
[7]

13.	(a)	(i)	dark	1
(ii)	because they are nocturnal / to avoid predation by being active at night	1
 
(b)	group A is able to maintain a rhythm while group B is not;
group B is active more frequently than group A;
group B is active for a shorter period than group A;	3

(c)	(before constant darkness) group B had a rhythm suggesting cytochromes are
not necessary;
	(after constant darkness) group B were unable to re-establish a rhythm
suggesting cytochromes are necessary;
cytochromes involved along with other variables;	2 max
[7]

14.	(a)	A: pinna;
B: eardrum;
C: stapes / bones of the middle ear;
D: semicircular canals;	2 max
Award [2] for 4 correct answers, [1] for three correct answers, [0] for two or one correct answer(s)
 
(b)	(a stimulus is) a change in the environment (internal or external) that
is detected by a receptor and elicits a response	1
 
(c)	the sympathetic and parasympathetic systems are part of the ANS;
the sympathetic and parasympathetic systems are antagonistic;
	the sympathetic system accelerates the heart rate and stimulates glucose
release (from the liver);
more blood is pumped to the muscles and the intestines;
the sympathetic system (mostly) uses norepinephrine (noradrenaline);
	the parasympathetic system slows down heart rate and stimulates the
stomach and the intestines;
body relaxes and blood flow slows down;
the parasympathetic system (mostly) uses acetylcholine;	4 max
[7]

15.	altruistic behaviour may be harmful to the animal itself but beneficial to other
animals;
occurs in social animals;
usually occur in the same species;
need not happen between genetically related animals from one population;
altruistic behaviour often occurs in animals which are genetically closely related;
altruistic behaviour may increase the survival rate of the group and thus the species;
helping close relatives or siblings increases the chances of passing on genes to the
next generation;
due to natural selection;
this is called inclusive fitness;
enhancing reproductive success of relatives is called kin selection;
if altruism was a negative trait it would / may have disappeared;
altruistic species do just as well as non altruistic species belonging to the same
order;
[6]

IB Questionbank Biology