1.
C
[1]
2.
D
[1]
3.
D
[1]
4.
B
[1]
5.
B
[1]
6.
A
[1]
7.
A
[1]
8.
A
[1]
9.
A
[1]
10.
A
[1]
IB Questionbank Biology
1
11.
B
[1]
12.
D
[1]
13.
(a)
(from 1960–2005) atmospheric CO2 concentration increases/strong
positive trend / increase between 1960–2005 of 65 ppm/figures to
that effect;
CO2 released by human activities contributes to the increase;
examples of human activities e.g. combustion of fossil fuels / deforestation;
seasonal/annual fluctuations (do not prevent long-term increase);
3 max
(b)
some human-induced change can be very large/perhaps catastrophic;
those responsible for the change must prove it will cause no harm before
proceeding;
appropriate (environmental/medical etc.) example e.g. companies must
immediately reduce emission of greenhouse gases even though proof
of human impact on global warming is still debated;
is reverse of historical practice / previously those concerned about
change had to prove it will do harm to prevent such changes from
going ahead / paradigm shift;
2 max
[5]
14.
(a)
total number of limpets increased
1
Award [1 max] if arrow direction reversed.
Award [1 max] for a correct food chain from green algae to named
species/limpet to oystercatcher.
2
(b)
(c)
(d)
L. strigatella decrease when oystercatchers excluded;
could be due to increase in number of L. digitalis;
increased competition/predation (for L. strigatella);
less food/green algae (for L. strigatella);
less habitat available (for L. strigatella);
(i)
X at 4th location going anticlockwise from top right
IB Questionbank Biology
3 max
1
2
(ii)
(e)
(f)
Y at 8th, 9th or 11th location going anticlockwise from top right
1
(overall) decline in limpet population;
in no location has the population increased;
greatest decrease in numbers at most northern/western locations;
in many/some/quantitative value locations the population has not changed;
2 max
more predation of the limpets than before;
less food available;
less habitat available;
more competition from other species;
water/air too warm for their metabolic activities/other specific reason;
water pollution / toxins;
2 max
[12]
15.
(a)
Award [1] for each of the following shown on a diagram of the
carbon cycle.
Award [5 max] for points not shown on a diagram.
The following show carbon which is static within the cycle at this
point in time.
carbon dioxide in air/water;
(sugars/carbon compounds in) plants/producers;
(carbon compounds in) animals/consumers;
(carbon trapped in) coal/oil/gas/fossil fuels;
The following should show arrows in direction of carbon flow.
carbon dioxide absorbed by plants/producers and used in
photosynthesis;
carbon dioxide released by (cell) respiration in plants/producers;
plants/producers eaten by animals/primary consumers/herbivores;
primary consumers eaten by secondary consumers;
carbon dioxide released by (cell) respiration in animals/consumers;
plants/animals die and are decomposed by (saprotrophic) bacteria/fungi;
carbon dioxide released by combustion of coal/oil/gas/fossil fuels;
carbon dioxide released by (cell) respiration in bacteria/fungi/
decomposers;
forest fires/combustion releases carbon dioxide from trees/plants;
carbon dioxide emitted by volcanoes;
IB Questionbank Biology
9 max
3
(b)
(c)
diagram of food chain showing at least three organisms and two
linkages with arrows showing direction of energy flow;
trophic level is a step/position in the movement/flow of energy
through an ecosystem;
(in a field situation) observe which organisms eat each other;
producer/name from example (first trophic level) does not eat other
organisms/captures energy through photosynthesis;
primary consumer/name from example (second trophic level) feeds
on producers;
secondary consumer/name from example (third trophic level) feeds
on primary consumers;
Since the command term is explain, the answer must be explicit to
gain marking points d–f. Named examples for producer and
consumers in diagram or explained example must represent
a coherent food chain. Reject chains using general names
such as fish or tree or grass. But, accept sardine or oak.
4 max
measure production of oxygen;
because oxygen is a by-product of photosynthesis;
example of technique for measuring oxygen production (count
bubbles/use sensors/other);
measure uptake of carbon dioxide;
because carbon dioxide is used during photosynthesis;
example of technique for measuring carbon dioxide production
(sensor, aquatic pH shift);
measure biomass of (batches of) plants;
increase in biomass gives (indirect) measure of rate of photosynthesis;
Since the command term is explain, reasons must be given to
receive full marks.
5 max
(Plus up to [2] for quality)
[20]
16.
(a)
food chains describe the feeding relationships between species;
arrows show (one) path of energy flow in an ecosystem / energy
flow described;
food chain with arrows pointing in the correct direction;
producer first step in chain;
three other named organisms making a realistic food chain;
Accept explicit common names exact enough to identify the food
source e.g. Oak not tree, sparrow not bird, rye grass not just grass, etc.
IB Questionbank Biology
4 max
4
(b)
(c)
global warming is an increase in temperature of the atmosphere/
oceans/Earth;
may result in climate change / changes in amount of precipitation /
greater ranges in temperature;
melting ice leads to rising of sea level;
leading to loss of habitat / example of organism that would lose
habitat;
changes in salinity / changes in ocean currents change distribution
of nutrients;
changes in predator-prey relationships (due to ecosystem disruption);
increased success of pest species;
temperate species with bigger range of habitats as ice melts;
increased rate of decomposition of detritus;
5 max
members of a population of the same species show variation;
some organisms are more likely to survive due to selective
advantage / survival of the fittest;
some organisms have a reproductive advantage;
these variations may be genetically controlled/heritable;
these genes are most likely to be passed on to offspring;
this can change the characteristic of the population;
bacteria can normally be killed with antibiotics;
antibiotics impose a selection pressure;
if a few bacteria have natural resistance to the antibiotic
they will survive;
if the resistance is heritable they will pass it on to their offspring;
they will reproduce/evolve to form bacterial colonies resistant
to the antibiotic;
example of organism selected by use of antibiotic;
(e.g. MRSA bacteria / resistant TB bacteria)
9 max
(Plus up to [2] for quality)
[20]
17.
(a)
x - axis labelled as time/ t and y - axis labelled as  Both labels needed.

number/ N/populatio n size;
 Do not accept “population” by itself.
oscillations of plateau
curve clearly showing the shape of the three phases; 
 phase notrequired
exponential/rapid growth phase labelled/highlighted properly; (accept log phase)
transitional/slowing phase labelled/highlighted properly;
plateau/no growth phase labelled/highlighted properly; (accept stationary phase)
carrying capacity/K drawn and labelled as a parallel line to
x-axis at plateau level;
4 max
IB Questionbank Biology
5
(b)
(c)
Accept examples of the points below, provided that the terms underlined
are clearly identified. Accept only named examples (Latin or common
names) from natural ecosystems only. Do not award marks for general
names such as “fish” or “tree”.
food chain shows transfer of nutrients/energy in an ecosystem /
arrows from one trophic level to the next in examples;
between different trophic levels / shown in a correct chain or web;
starting with a producer;
followed by at least two levels of consumers / shown in a correct
chain or web;
food web is the (branched) interaction of multiple food chains /
cross arrows in examples;
using (multiple) producers as a source;
transferring nutrients/energy to consumers from different food chains;
same consumer could be at different trophic levels in a food web;
6 max
Award [2 max] from the following list of greenhouse gases:
water vapour;
carbon dioxide;
methane;
oxides of nitrogen;
all (of these gases) occur naturally;
and human activity has increased the normal level of these gases in
recent years;
incoming shorter wave radiation from the Sun;
is re-radiated as longer wave radiation/infrared;
(mainly) in the form of heat;
captured by greenhouse gases;
which increases the atmospheric/ocean temperature;
at a higher rate than normal / creating a positive imbalance;
which threatens ecosystems/climatic patterns/ocean patterns;
Earth’s history had many fluctuations in gas levels/global
temperature / some scientists are skeptical about enhanced
greenhouse effect;
8 max
(Plus up to [2] for quality)
[20]
IB Questionbank Biology
6
18.
(a)
Award [1] for each structure clearly drawn and correctly labelled, up to [4 max].
cell wall — a uniformly thick wall;
pili — hair-like structures / flagellum — at least length of the cell;
May be labelled as the
plasma membrane represented by a continuous single line; 
innermost wall line.
ribosomes — drawn as small discrete circles/shaded circles;
nucleoid — region with DNA not enclosed in membrane;
plasmid — circular ring of DNA;
cytoplasm —the non-structural material within the cell;
Award [3 max] if one eukaryote structure is shown, [2 max] for
two eukaryote structures, [1 max] for three eukaryote structures
and [0] if four or more eukaryote structures are shown.
(b)
4 max
light: [2 max]
rate increases with increasing light;
it reaches maximum then plateaus;
as all chloroplast molecules are working at optimal pace;
temperature: [2 max]
rate increases with increasing temperature;
to a maximum/optimum temperature;
but then falls off rapidly;
as enzymes are denatured above the optimal temperature;
carbon dioxide: [2 max]
rate increases with increasing carbon dioxide level;
it reaches maximum then plateaus;
as photosynthesis operating at optimal level;
Award any of the above points if clearly drawn in a diagram.
(c)
6 max
increase in temperature is called global warming;
this is caused by the greenhouse effect;
a natural phenomenon that has occurred over millions of years;
main gas responsible is carbon dioxide;
other gases like methane/nitrous oxide also cause effect;
shortwave radiation from the Sun enters atmosphere;
warms the surface of the Earth;
longwave radiation emitted by the surface of the Earth;
is absorbed by carbon dioxide/greenhouse gases;
human use of fossil fuels has increased levels of atmospheric carbon dioxide;
rapid rise in temperatures over (approximately) hundred years;
cows/animals/peat bogs release methane;
greenhouse gases emitted by volcanic activity;
8 max
(Plus up to [2] for quality)
[20]
IB Questionbank Biology
7
19.
(a)
(b)
(c)
Award [1] for each of the following clearly drawn and correctly labelled.
clear ruled axes, labelled time on the x- and population size on the y- axis;
exponential phase annotated to indicate rapid population growth because of
abundant resources;
transitional phase annotated to indicate a developing shortage of resources and
increase competition between members of the population;
plateau phase annotated to indicate a population now constrained by resource
availability / natality equals mortality;
melting of permafrost;
increased detritus decomposition;
expansion of temperate species / reduced range for arctic species;
example of an affected species;
examples of human activity;
rise in sea levels;
change in climatic patterns;
loss of ice habitat;
more pests / pathogens;
disturbance to food chains / webs / trophic levels;
4
6 max
parents produce more offspring than required to keep numbers constant;
more are produced than the environment can support;
example of an environmental condition;
these offspring show variation;
some are better adapted than others to the environment;
these tend to survive to breed themselves;
characteristics are inheritable;
so the new generation has these characters too;
this leads to changes in the population as a whole;
these changes constitute evolution;
8 max
(Plus up to [2] for quality)
[20]
20.
(a)
(i)
oxygen concentration falls as temperature rises / negative correlation/
inverse relationship;
steady decline below 4.2/4.3/4.4°C / vice versa:
rapid decrease between 4.2/4.3/4.4°C and 5°C;
zero oxygen concentration at/above 9 °C;
2 max
(ii)
warmer water can hold less oxygen / lower oxygen solubility as
temperature rises;
lower oxygen concentration of water reaching gills / less oxygen
available from the water to diffuse into the gills;
higher metabolic rate / faster rates of respiration / more oxygen
consumption as temperature rises;
IB Questionbank Biology
2 max
8
(b)
not enough energy/ATP/aerobic respiration (for muscle contraction/movement)
(c)
(i)
(ii)
(d)
(i)
(ii)
(e)
(i)
1
rising trend overall;
annual rise and fall / fluctuations;
2
(CO2 emissions from) increased burning of fossil fuels/deforestation/
other anthropogenic factor;
variation in photosynthesis rates during the year / variations in CO2
uptake in the oceans;
2
diffusion in both directions during each year;
diffusion from atmosphere to water during most of the year;
diffusion from water to atmosphere for part of year/autumn/fall/
seasonal;
increasing diffusion from water to atmosphere in later years;
2 max
(no net diffusion because) concentrations will become equal / there
will be no gradient;
water concentration higher than atmospheric concentration as often
as atmospheric concentration higher than water concentration;
1 max
300 ppm (Allow answers in the range 295–305 ppm) unit must be
included to earn mark.
1
3.3°C (Allow answers in the range 3.0–3.3°C) unit must be
included to earn mark.
N.B. A maximum of [1] per exam can be deducted for a
missing unit.
1
(f)
positive correlation / higher temperature with higher CO2 concentration
1
(g)
oceans may cease to act as sink / store for CO2;
atmospheric CO2 concentration may then rise more rapidly;
atmospheric CO2 concentration is higher than for at least 400 000 years/
any time in recent (geological) time;
Antarctic temperatures will (probably) rise higher than at any time in
400 000 years/any time in recent (geological) time;
rising (sea water) temperature would reduce oxygen availability in water;
significant changes in habitat/abiotic factors;
populations may not be able to adapt;
(ii)
3 max
[18]
IB Questionbank Biology
9
21.
(a)
(b)
(c)
standard deviation summarizes the spread of values around the mean / 68%
of all values fall within one standard deviation of the mean / gives a measure
of variability of the data / OWTTE
1 max
November had 113 (+2) ciliates ml1 sediment (units required)
production by treated and untreated samples is almost the same;
production by untreated samples is usually slightly higher than treated
samples;
except November, January when the treated samples have a slightly higher
methane production;
1
2 max
(d)
endosymbionts do not seem to be responsible for methane production;
methane production is almost the same whether the ciliates are alive
(untreated samples) or killed (treated samples);
no apparent correlation between methane production and number of
ciliates;
months when the population of ciliates is highest are not the months
when the methane production is highest / ciliate numbers high in November
when methane production is low / methane production highest in July and
August when ciliate numbers are not high;
2 max
(e)
greenhouses gases collect in atmosphere;
layer of gases allows incoming short-wave radiation (from sun) to pass
through to earth’s surface where it is converted to longer-wave radiation;
long-wave radiation cannot all pass through layer of gases but some
reflected back to earth causing earth’s surface to become warmer;
(f)
(g)
(h)
(i)
2 max
first name / Nacella refers to the genus and the second name / concinna
refers to the species
1
negative correlation / inversely proportional / as temperature increases the
percentage righting in N. concinna decreases
1
percentage of N. concinna able to right themselves decrease by 50% /
decreases from 95% to less than 50% / less than half able to right
themselves
1
model suggests two degree rise in temperature which would mean summer
temperatures of 3C;
at this temperature less than 50% of organisms able to carry out basic
behaviour;
decreased survival of species / decreased ability to avoid predation;
2 max
[13]
IB Questionbank Biology
10