IB Ecology Questions
1.
Which of the following is the best definition of a population?
A.
A group of individuals that can interbreed and produce fertile offspring
B.
The number of individuals of the same species in a given area
C.
A group of species living and interacting with each other in a given area
D.
The total number of individuals in a given area
(Total 1 mark)
2.
The diagram below shows a simplified food web.
What is the role of the snake in this food web?
A.
Primary consumer
B.
Secondary consumer
C.
Tertiary consumer
D.
Producer
(Total 1 mark)
3.
The graph below represents a sigmoid (S-shaped) population growth curve. Three sections of
the curve are indicated (1, 2 and 3).
In which of the sections is natality plus immigration greater than mortality plus emigration?
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A.
4.
5.
1 only
B.
2 only
C.
1 and 2 only
D.
3 only
Two different trees have been classified as Pinus pinea and Pinus nigra. Which of the following
statements is correct?
A.
Both trees belong to the same class but a different genus.
B.
Both trees belong to the same family and same genus.
C.
The species name of both trees is Pinus.
D.
The family names are pinea and nigra.
A collection of four animal specimens is observed and a dichotomous key is applied. Which
specimen is an arthropod?
1.
Non-segmented body ......................................... go to 2
Segmented body ................................................. go to 3
2.
Body is not symmetrical ..................................... specimen A
Body is symmetrical ........................................... specimen B
3.
Jointed appendages present ................................ specimen C
Jointed appendages absent ................................. specimen D
A.
Specimen A
B.
Specimen B
C.
Specimen C
D.
Specimen D
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6.
Which of the following ecological units includes abiotic factors?
A.
A community
B.
An ecosystem
C.
A population
D.
A trophic level
(Total 1 mark)
7.
In the forest zone between Gabon and the Republic of Congo it is estimated that an epidemic of
the Zaire strain of the Ebola virus (ZEBOV) killed nearly 5000 gorillas, significantly reducing
the population. Which statement is supported by this information?
A.
Natality was greater than mortality.
B.
Mortality was equal to natality.
C.
Natality and immigration was greater than mortality and emigration.
D.
Mortality was greater than immigration and natality.
(Total 1 mark)
8.
If humans become infected with the Ebola virus it can have devastating effects. Strong, but not
certain, evidence suggests that trading in animal products is the main reason for the spread of
the Ebola virus to humans. Which statement about the precautionary principle is correct?
A.
In the absence of certainty about cause and effect, people should not be asked to stop
trading in animal products.
B.
The burden of proof regarding a cause and effect relationship lies with scientists.
C.
Because it is a probable cause, trading in animal products should be banned because of
the potentially devastating consequences.
D.
The precautionary principle is not relevant in this case.
(Total 1 mark)
9.
Which group of organisms in the carbon cycle converts carbon into a form that is available to
primary consumers?
A.
Decomposers
B.
Saprotrophs
C.
Detritus feeders
D.
Producers
(Total 1 mark)
10.
Up to two additional marks are available for the construction of your answers.
(2)
(a) Living organisms at every trophic level are part of the carbon cycle. Draw a labelled
diagram of the carbon cycle to show the processes involved.
carbon dioxide in air/water; (sugars/carbon compounds in) plants/producers; (carbon
compounds in) animals/consumers; (carbon trapped in) coal/oil/gas/fossil fuels;
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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;
b)
Explain, using an example of a food chain, how trophic levels can be deduced.
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.
(c)
Explain methods that can be used to measure the rate of photosynthesis.
measure production of oxygen;
because oxygen is a by-product of photosynthesis;
example of technique for measuring oxygen production (count
bubbles/use sensors/other);
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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;
11.
Up to two additional marks are available for the construction of your answers.
(a) Describe what is meant by a food chain using an example with four named
organisms.
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;
4 max
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.
(b)
Outline how global warming may affect arctic ecosystems.
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;
(c)
Explain how natural selection can lead to evolution using antibiotic resistance in bacteria
as an example.
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;
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(e.g. MRSA bacteria / resistant TB bacteria)
12.The graph below shows the monthly mean values of terrestrial invertebrates from May 1997 to
June 1998 in the northern hemisphere. The light line shows the biomass of invertebrates which are
prey to forest birds (terrestrial invertebrate biomass). The darker line shows the invertebrates which
lived in the stream and have moved to the forest (aquatic invertebrate flux or movement). The black
bars on the horizontal line at the bottom show periods when trees have leaves and the white bars show
periods of defoliation.
(a)
State the mean terrestrial invertebrate biomass measured in August.
166 mg m–2
(b)
Describe the trend in the aquatic invertebrate flux.
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;
(c)
Suggest the relationship between defoliation and the amount of terrestrial invertebrates in
the forest.
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;
(d)
Suggest a possible explanation for the pattern in aquatic invertebrate flux to the forest
seen between the months of June and December.
(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;
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(adult forms) move to utilize (changes in) food supply in forest;
13.
(a) Define the terms fundamental niche and realized niche.
Fundamental niche:
the potential niche / the niche the organism could occupy under ideal conditions / the full
mode of existence given the adaptations of the species / OWTTE;
Realized niche:
the actual niche / the niche restricted by competition and environmental variables / the
niche resulting from the limits placed on the species / OWTTE; 2
(b)
Explain why the carnivores in an ecosystem tend to be fewer in number and have a
smaller biomass than the herbivores in the same ecosystem.
energy transfer along the food chain is less than 100% efficient; 10% energy transfer
between trophic levels;
nutrient transfer is less than 100% efficient; each carnivore needs to consume many prey
organisms; tendency for size of organisms to increase as trophic level increases; 2
max
(2)
(c)
Explain why carnivores tend to be more affected by biomagnification than organisms
lower down the food chain.
mercury / DDT / other named example; biomagnification is the accumulation of
chemicals through the food chain; chemicals that undergo biomagnification are
stored/not broken down (in the bodies of the organisms that consume them); chemicals
are passed (unaltered) from one trophic level to the next; chemicals become more
concentrated in the bodies of each (subsequent) trophic level; organisms higher up the
food chain consume larger amounts of the chemical; 3 max
(3)
(Total 7 marks)
14.
The introduction of alien species and the release of environmental pollutants are examples of
human activities that have an impact on the environment.
(a)
Alien species may arrive in an ecosystem due to accidental or deliberate release.
State the impact of one named example of deliberate release.
example e.g. Cane Toads/Bufo marinus
effect e.g. predation of native invertebrates
Other examples/effects:
Example
Effect
Salvinia (Floating fern/Giant
Salvinia/Kariba weed)
or
Water Hyacinths
blocked waterways excessive decomposition
depletes oxygen and fish stocks
Nile Perch
destroyed native fish species (in Lake
Victoria)
Yellowjackets (German wasps —
nests in buildings and threat of stings due to
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North America)
aggressive behaviour
Rabbits (in Australia)
loss of native plant species erosion due to
excessive herbivory
(2)
(b)
Outline the effect of CFCs on the ozone layer.
UV light causes CFCs to release chlorine; CFCs cause ozone to form oxygen (by
chlorine atoms reacting); causes a reduction in ozone concentration (allowing more UV
to enter); increases the ozone hole; particularly effective in the Antarctic spring; effective
in very low concentrations / a small amount of CFC can destroy a large amount of ozone
(2)
(Total 4 marks)
15.
Competition between genetically similar species of birds may lead to changes of one or more
characteristics. One characteristic that results from this kind of selection is differences in the
beaks. Researchers studied the beak lengths of two species of warblers. The graphs below show
the beak lengths of Pine Warblers (Dendroica pinus) and Yellow-throated Warblers (Dendroica
dominica) from three geographically isolated areas in the USA.
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[Source: R Ficken et al. 1968. Evolution. Vol 27. Pp 307–314. Republished with the permission of Wiley-Blackwell.]
(a)
(i)
Identify the species with the shortest mean beak length.
Pine Warblers/Dendroica pinus (of Delmarva)
(1)
(ii)
Determine the difference in the mean beak length of the two populations of Yellowthroated Warblers in Midwest and Delmarva.
2.6 mm (accept answers in the range of 2.5 mm to 2.7 mm)
(1)
(iii) Compare the range of variation in beak length of the Yellow-throated Warblers in
Midwest to the beak length of the Yellow-throated Warblers in Delmarva.
Yellow-throated Warblers have a bigger range / greater variation (of beak length)
in Delmarva than in Midwest (accept numerical values)
(1)
(b)
Suggest an advantage for the longer beaks of Yellow-throated Warblers in Delmarva.
allows them to eat other foods / changes feeding behaviour; reduces competition with
Pine Warblers
(1)
(c)
Using the Yellow-throated Warbler as an example, outline the concept of allopatric
speciation.
allopatric speciation occurs between populations that live in different areas; (when
populations are geographically isolated) there is no interbreeding; natural selection
works on each population independently; competition with the Pine Warbler only occurs
in Delmarva / the Pine Warbler acts as selective pressure on the Yellow-throated Warbler
in Delmarva; eventually Yellow-throated Warblers in the two areas could become two
species instead of one / OWTTE
(3)
(Total 7 marks)
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16.
Cadmium is a heavy metal that can be toxic to many species. In a study, the concentration of
cadmium was examined in the tissues of three soil arthropods, Neobisium muscorum,
Platynothrus peltifer and Notiophilus biguttatus. The shaded area of each graph indicates the
time that the organisms were exposed to cadmium in their environment, while the unshaded area
indicates the time when cadmium was not present in their environment.
[Source: M P M Janssen. 1991. “Comparison of cadmium kinetics in four soil arthropod species.” Archives of
Environmental Contamination and Toxicology. Vol 20. P 3.]
(a)
Identify the highest average concentration of cadmium found in P. peltifer.
260 pmol mg–1 (accept answers in the range of 255 pmol mg–1 to 265 pmol mg–1) 1
(1)
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(b)
Determine, with a reason from the data, which species is unable to eliminate cadmium.
Neobisium muscorum; level of cadmium remains high / does not decrease (when
cadmium is removed);
(2)
(c)
(i)
State the species that accumulates the least cadmium.
Notiophilus biguttatus
(1)
(ii)
Suggest, with observations from the data, a reason why the species stated in (c)(i)
accumulates the least cadmium.
can excrete/remove/eliminate cadmium (from its tissues); faster
reduction/removal / drops to lowest level after cadmium exposure; cadmium levels
stop rising sooner/rise slowing by day ten; is less tolerant/dies when cadmium
reaches a certain concentration; exposed to cadmium for a shorter time/period
(2)
(d)
Describe the possible effects of the presence of cadmium in food chains involving these
arthropods.
cadmium accumulates along food chain / biomagnification / bioaccumulation; heavy
metals cause abnormal growth/behaviour/death/failure to reproduce; Notiophilus
biguttatus has less effect on the food chain (as it accumulates less); cadmium
harmful/lethal to organisms at/near the end of the food chain; (death of arthropods) may
change soil quality
(2)
(Total 8 marks)
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17.
(a) Explain the concept of an ecological niche.
(ecological niche is) mode of existence/role of an organism within its ecosystem;
(ecological niche includes) its habitat/abiotic factors of the environment; (ecological
niche includes) what the species eats / how the species obtains food; (ecological niche
includes) interactions with other species;
(ecological niche includes) the set of all ranges of limiting factors an organism tolerates /
OWTTE
(2)
(b)
Distinguish between fundamental niches and realized niches.
fundamental niche is the niche for which a species has adaptations for success/potential
mode of existence whereas a realized niche of a species is its actual mode of existence;
the realized niche is often smaller than the fundamental niche (of a species);
competition/predation is reason for the differences (between fundamental and realized
niches)
(2)
(Total 4 marks)
18.
(a) Outline characteristics of a named biome.
correctly named biome; temperature range; dominant plant/ecosystem characteristics
e.g.: temperate deciduous forest; warm/15–18°C summers and cold/3–7°C winters /
significant annual temperature variation; broad leaf trees (that lose leaves annually) /
significant diversity of understory plants;
Further examples:
named biome
temperature range
dominant plant / ecosystem
characteristics
desert;
hot (30°C+) in day and cold
(below zero) at night;
xerophytes / succulent /
sparse low-lying bushes
adapted to water
conservation;
savannah;
hot (20–30°C);
grasslands with widely
spaced trees;
tropical rainforest;
very hot (25–30°C);
epiphytes / trees and wide
leaf plants in undergrowth /
huge diversity / tall mature
trees of many species;
taiga;
cold (below 0–15°C);
coniferous/evergreen trees
densely packed (few species);
tundra;
minus temperatures for most
of the year;
small and close to ground /
grasses and mosses with a
few small trees (perennial
herbs grow in summer);
(3)
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(b)
Explain the factors that affect the distribution of animal species.
animal distribution is related to abiotic and biotic (niche) requirements; temperature
must be within viable range based upon the adaptations of the animal;
water must be available in species-specific quantities (Gila lizards require less water
than elephants); breeding sites are required for maintenance of the species; food supply
must be of the right kind for the species (e.g. nuts for squirrels and leaves for rabbits);
territory is required for some species for breeding/feeding; dissolved oxygen affects
aquatic species as some organisms can tolerate low levels of oxygen; salinity affects
distribution as some species are more sensitive than others to salt; other appropriate
answers with justification are acceptable;
(3)
(Total 6 marks)
19.
What is a community composed of?
A.
Habitats
B.
Populations
C.
Abiotic factors
D.
Biotic and abiotic factors
(Total 1 mark)
20.
Which of the following are greenhouse gases?
I.
Oxides of nitrogen
II.
Carbon dioxide
III.
Methane
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
(Total 1 mark)
21.
The population of white-tailed deer in Nova Scotia (Canada) suffered a significant decline in the
late 1970s. Which of the following is most likely to have caused the decline?
A.
The population had depleted resources in the environment
B.
A decrease in hunting
C.
A decrease in predation
D.
Natality and immigration exceeded mortality and emigration
(Total 1 mark)
22.
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What do all of the organisms in the diagram represent when considered together?
A.
A food chain
B.
A population
C.
A community
D.
An ecosystem
(Total 1 mark)
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23.
The air in urban areas contains a variety of pollutants, including particles of solids and gases.
The table below shows the pH of rain in urban areas of New York and rural areas nearby.
The concentration of four air pollutants is also shown. The concentrations of gases are measured
in parts per billion (ppb).
Area
Lead /
μg m–3
Nitrogen dioxide /
ppb
Nitrous oxide /
ppb
Sulfur dioxide /
ppb
pH of rain
Urban
0.09
37.7
39.3
18.7
4.3
Rural
0.04
6.2
0.5
2.3
4.2
[Source: Nature by Nature Publishing Group. Reproduced with permission of Nature Publishing Group in the format
Journal via Copyright Clearance Center.]
(a)
(i)
Compare the acidity of rain in urban and rural areas.
both (moderately) acidic / similar acidity / rural (slightly) more acidic / lower
pH/converse 1
(1)
(ii)
Compare the levels of atmospheric pollution in urban and rural areas.
urban areas have overall more (atmospheric) pollution/converse; levels of each
pollutant are much higher concentrations in urban areas; qualified by correct
example e.g. more solid pollution/more lead e.g. nitrous oxide is almost eighty
times higher in urban areas; 2 max Comparative terms are required to award the
mark.
(2)
Tree planting has been suggested as a way of improving air quality in urban areas. The growth
of Populus deltoides in urban and rural areas near New York was investigated. Trees were
grown in pots containing the same type of soil in all areas. High levels of mineral nutrients in
the soil ensured that lack of nutrients was not the limiting factor on growth rates. The growth of
the trees above ground (shoot biomass) and below ground (root biomass) was measured after
one year. The bar chart below shows the results for two rural areas (open bars) and four urban
areas (filled bars).
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[Source: Nature by Nature Publishing Group. Reproduced with permission of Nature Publishing Group in the format
Journal via Copyright Clearance Center.]
(b)
Outline the conclusions that can be drawn about the growth of Populus deltoides from the
data in the bar chart.
(overall) growth/biomass was greater in urban areas; greater growth/biomass in urban
areas for roots / below ground; greater growth/biomass for shoots / above ground;
growth/biomass was (more) variable in urban areas; shoot/above ground growth/biomass
always greater than root biomass;
(2)
(c)
Discuss whether the differences in growth rates of Populus deltoides between urban and
rural areas could be due to
(i)
differences in the acidity of rain.
unlikely to be the cause because differences in pH are small 1
(1)
(ii)
differences in the concentration of air pollutants.
yes because higher growth in areas where there is higher pollution; might not be
cause / correlation rather than cause and effect; pollutant might have stimulated
growth / acted as fertilizer in urban areas; (no because) pollutant did not
negatively affect growth (as more pollution in urban areas/area with higher
growth);
(2)
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The histograms below show the range of ozone exposure between May and September in urban
and rural areas near New York.
[Source: Nature by Nature Publishing Group. Reproduced with permission of Nature Publishing Group in the format
Journal via Copyright Clearance Center.]
(d)
Compare the seasonal ozone exposures in urban, agricultural and forested areas.
lowest ozone exposures in urban areas / highest ozone exposure in rural/agricultural
areas; lower ozone exposure in forested than agricultural areas; highest range in
agricultural areas / lowest range in forested areas; wide range of ozone exposures in
each area;
(2)
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The concentrations of ozone and the shoot growth of Populus deltoides were measured at eight
sites. The results are shown in the scattergraph below.
[Source: Nature by Nature Publishing Group. Reproduced with permission of Nature Publishing Group in the format
Journal via Copyright Clearance Center.]
(e)
Using the data in the scattergraph and in previous parts of this question, suggest a
hypothesis for differences in the growth of Populus deltoides between urban and rural
areas. Give reasons for your hypothesis.
(strong) negative correlation/lower shoot biomass/less growth with higher ozone
exposure; ozone exposure is lower in urban areas/other reference to graph;
ozone is toxic/damages plants impacts photosynthesis; (hypothesis is) higher growth
rates (in urban areas) are due to lower ozone exposure; (hypothesis is) both
factors/ozone and air pollution may have played a role in growth differences; 3 max Do
not accept hypotheses involving pH. Accept converse of above points.
(3)
(Total 13 marks)
24.
Up to two additional marks are available for the construction of your answers.
(2)
(a) All organisms in an ecosystem are involved in the carbon cycle. Outline the roles of
living organisms in the carbon cycle.
plants/producers fix carbon (dioxide)/use carbon (dioxide) in photosynthesis;
sugars/carbon compounds (produced) in plants/producers from photosynthesis;
(carbon compounds in) plants/producers eaten by animals/primary
consumers/herbivores; (carbon compounds in) primary consumers eaten by
secondary consumers/ passed along food chain; carbon compounds/sugars/organic
molecules digested and absorbed by consumers; carbon dioxide released by cell
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respiration (in plants/animals/ consumers); plants/animals die and are decomposed
by (saprotrophic) bacteria/fungi; carbon dioxide released by cell respiration in
bacteria/fungi/ decomposers; enzymes released to digest/hydrolyse carbon
compounds in organic matter; forest fires/combustion releases carbon dioxide;
humans burn fossil fuels adding carbon dioxide to the atmosphere; 8 max Award any
of the above points if clearly drawn in an annotated diagram.
(8)
(b)
Explain how triose phosphate is produced and used in the chloroplasts of a plant.
ribulose bisphosphate/RuBP and carbon dioxide react together; (this is) carbon
fixation/part of light-independent reactions; catalysed by RuBP carboxylase/Rubisco;
glycerate 3-phosphate/GP produced; glycerate 3-phosphate/GP reduced/converted to
triose phosphate/TP; using NADPH/(NADPH+H+) and ATP; from the lightdependent reactions; some triose phosphate used to regenerate RuBP; some triose
phosphate used to synthesize glucose (phosphate)/starch
(5)
(c)
Explain the conditions that are needed to allow a seed to germinate.
water needed to rehydrate the seed; gibberellin released / active after water absorbed;
gibberellin needed to produce amylase; water needed to allow substances inside the
seedling to be transported; oxygen needed for (aerobic) cell respiration; warmth
needed to speed up metabolism/enzyme activity; warmth indicates that it is a favourable
season for germination/spring; some seeds need a cold period to stimulate
germination; some seeds need fire to stimulate germination; some seeds need to pass
through an animal (gut) to stimulate germination
(5)
(Total 20 marks)
25.
(a)
The food web below shows some of the feeding relationships found between the organisms
living in or near a river in England.
Identify an organism in the food web that is
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(i)
an autotroph.
diatoms / (other) algae 1
(1)
(ii)
both a secondary and tertiary consumer.
trout
(1)
(b)
Explain how the flow of energy in the food web differs from the movement of nutrients.
nutrients are recycled in a food web and energy enters and leaves/is not recycled;
nutrients are recycled by saprotrophs/returned to environment and reused; while energy
(enters as light and) is dispersed as heat
(2)
(c)
Discuss reasons why the levels of a pyramid of energy differ in size.
(the shape of pyramid) shows energy lost from base to top of pyramid/80 to 90% lost
at each trophic level; (because) energy is used/released through cell respiration/heat/
metabolism/movement (at each trophic level); not all tissues are eaten i.e.
bone/hair/cellulose/excretion/ undigested/die (so energy is not available for next
trophic level)
(2)
(Total 6 marks)
26.
(a) (i)
State the name of the biome in which there is little precipitation and
temperatures are very low.
tundra1
(1)
(ii)
Outline the characteristics of the vegetation of this biome.
absence of tall trees/tall plants; lichens/mosses/sedges/small grasses/annuals;
short growing/flowering season;
(1)
(b)
Outline the consequences of the edge effect for small nature reserves.
edge effect is the contrast between different environments/from central area of reserve;
small reserves have more edge effect; as fragmentation increases so does edge (effect);
example of edge effect (e.g. cowbirds that lay eggs in edge will increase)
(2)
(c)
Outline one example of biological control of invasive species.
example of invasive species; example of biological control; 2
e.g. to control the cottony cushion scale (Icerya purchasi) (a pest that was devastating the
California citrus industry in the late 1800s); the vedalia beetle/a predatory insect
(Rodolia cardinalis) was introduced (from Australia);
(2)
(Total 6
marks)
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27.
Some organisms have adopted r-strategies and some have adopted K-strategies. Discuss the
environmental conditions that favour each of these strategies.
r-strategy occurs in unstable environment/where there are ecological disruptions; resources
used to maximize reproducing (once); for example in coastal rock pools / other example;
pathogens/pest species have r-strategies / other example of r-strategy organism; in
stable/predictable environments K-strategy predominates;
more resources are invested for long-term survival; for example in forests / other example; trees
/ humans / whales / other example of K-strategy organism; difficult to determine strategy / rand K-strategies represent two extremes in a range of strategies;
(Total 6 marks)
28.
(a) Climograph A below shows a tropical steppe which is a form of grassland.
Deduce, with a justification, the type of biome represented by climograph B.
tropical rainforest; because the climate is warm/hot all year; because of the high level of
rainfall/precipitation all year; 3
(3)
(b)
Define indicator species.
species sensitive to certain environmental conditions / species used to monitor
environmental change / species used to determine environmental conditions 1
(1)
(c)
Outline, with a named example, biological control of invasive species.
name of species to be controlled; method of biological control with species name of
predator/parasite/ pathogen; 2
e.g. rabbits (introduced into Australia); controlled by release of myxoma virus /
myxomatosis (from South America); Allow any other verifiable example.
[Reject cane toads as a biological control agent and other unsuccessful cases.]
IB Questionbank Biology
21
(2)
(Total 6 marks)
29.
Outline either r-strategies or K-strategies.
r-strategy: many offspring (at a time/per brood); little care of offspring; high mortality rate /
only a small proportion reach maturity; small (body) size; short lifespan / fast maturation /
reproduce at a young age; reproduce only once; favoured by unstable/changing environment /
opportunists / broad niches; pioneer species; variable population size;
or
K-strategy:
few offspring (at a time/per brood); much care of offspring; low mortality rate / large
proportion reach maturity; large (body) size; long lifespan / slow maturation / reproduce at
advanced age; reproduce repeatedly; favoured by stable/consistent environment / broad niches;
climax species; stable population size;
(Total 6 marks)
30.
What is a community?
A.
A group of organisms living and interacting in the same trophic level
B.
A group of populations living and interacting in a food chain
C.
A group of organisms of the same species living and interacting in an ecosystem
D.
A group of populations living and interacting in an area
(Total 1 mark)
31.
What are the units of a pyramid of energy?
A.
kJ m–2 yr–1
B.
kJ m–1 yr–1
C.
J m–3 s–1
D.
J m2 s–1
(Total 1 mark)
32.
What is a potential consequence of the rise in global temperatures on the Arctic ecosystem?
A.
Increased exposure to UV light
B.
Increased rate of decomposition of detritus
C.
Decreased success of pest species
D.
Increase in the ice habitat available to polar bears
(Total 1 mark)
33.
What can limit increases in population size?
I.
Decrease in prey
II.
Decrease in parasites
IB Questionbank Biology
22
III.
Increase in predators
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
(Total 1 mark)
34.
A poodle and a chihuahua are both dogs and classified as Canis familiaris. What conclusion can
be made?
A.
They belong to the same genus but not the same species.
B.
They are the same species but not the same genus.
C.
They are different species but can interbreed.
D.
They belong to the same genus and are the same species.
(Total 1 mark)
35.
This question is about the food web below.
[Source: http://cbc.amnh.org/crisis/foodweb.html. Center for Biodiversity and Conservation, American Museum of
Natural History]
What will happen to the sizes of the populations in the food web above if the sea otter
disappears?
IB Questionbank Biology
23
A.
Large fish increase and sea urchins decrease.
B.
Abalones increase and sharks increase.
C.
Sea urchins increase and kelps decrease.
D.
Sea stars decrease and sharks increase.
(Total 1 mark)
36.
Which gas will enhance the greenhouse effect if released into the atmosphere?
A.
Hydrogen
B.
Oxide of nitrogen
C.
Oxygen
D.
Nitrogen
(Total 1 mark)
37.
What do the graphs below show?
A.
Population in the United States is increasing at a higher rate.
B.
Infant death rate is high in both countries.
C.
Males live longer than females in both countries.
D.
Birth rate is higher in Mexico than in the United States.
(Total 1 mark)
IB Questionbank Biology
24
IB Questionbank Biology
25
39.
The grey partridge (Perdix perdix) is a species of bird that is found on farmland. Sparrowhawks
(Accipiter nisus) and buzzards (Buteo buteo) are birds of prey that kill and feed on birds,
including grey partridge. The number of grey partridges in a region of southern England was
monitored from 1970 to 2004. The numbers of sparrowhawks and buzzards, seen from sampling
positions during regular observation periods, were counted. The results are shown in the graph
below.
[Source: Watson, M et al. 2007. Journal of Applied Ecology. Vol 44. Pp 972–982. Reproduced with the permission of
Wiley Blackwell.]
(a)
Outline the trends, over the period of time shown in the graph, in the number of grey
partridges, buzzards and sparrowhawks.
Grey partridges: grey partridge numbers/pairs reduced
Buzzards: buzzard numbers increased
Sparrowhawks: sparrowhawk numbers no clear trend/no overall rise or fall
(3)
The density of grey partridge (number per square kilometre) varied considerably in different
areas within the study region. The graph below shows the correlation between the density of
grey partridges and the density of birds of prey.
IB Questionbank Biology
26
[Source: The Journal of Applied Ecology by BRITISH ECOLOGICAL SOCIETY. Reproduced with permission of
BLACKWELL PUBLISHING LTD. in the format Journal via Copyright Clearance Center]
(b)
(i)
Identify the correlation between the density of grey partridges and birds of prey.
Negative correlation/inverse proportion/bird of prey density falls as partridge
density rises
(1)
(ii)
Suggest a hypothesis to account for this correlation.
Partridges eaten by birds of prey; fewer partridges present where more birds of
prey present / more partridges present where fewer birds of prey present;
partridges move to areas with fewer birds of prey; fewer birds of prey enable
growth (by reproduction) of grey partridge population
(2)
The highest density of birds of prey was found in areas used for recreational shooting. In these
areas, other species of partridge were bred and released. Food and shelter were provided for the
released birds. These measures tended to increase the number of both released and wild birds.
The causes of death of grey partridge were investigated in one of the areas that was used for
recreational shooting. The pie chart below shows the causes of death.
IB Questionbank Biology
27
(c)
(i)
Calculate the percentage of deaths due to birds of prey.
18 %
(1)
(ii)
Using the data provided, discuss the causes of the correlation between the density
of grey partridges and the density of birds of prey.
 Birds of prey attracted from outside to shooting areas because of
abundant food (grey and released partridges) / birds of prey
living in shooting areas increase in numbers because of abundant food
 Non-hunting human involvement (food and shelter) influenced
the correlation between the densities
 More grey partridges shot than killed by birds of prey / many
grey partridges shot in shooting areas
 Correlation not only due to birds of prey eating grey partridges/
human involvement
 Grey partridges compete with released partridges for food
and shelter (decreasing the density of grey partridges)
(3)
(d)
Suggest a conservation measure that would be most likely to prevent the extinction of
grey partridges from southern England.
 Limit/ban shooting of grey partridge
 Train shooters to recognize difference between grey partridge and
other species of partridge
 Protect/restore habitat of grey partridge
 Promote captive breeding of grey partridge (for release into ecosystem)
 Remove birds of prey/foxes depending on laws
(1)
(Total 11 marks)
40.
Up to two additional marks are available for the construction of your answers.
(2)
(a)
Plants are a diverse group of eukaryotic organisms. Describe the different characteristics
of the bryophyta, filicinophyta, coniferophyta and angiospermophyta.
bryophyta have no roots / only have rhizoids;
bryophyta have simple leaves/stems / only a thallus;
bryophyta produce spores in capsule;
byrophyta are nonvascular;
bryophyte exhibit (pronounced) alternation of generations / a
significant gametophyte generation;
IB Questionbank Biology
28
filicinophyta have roots, stems and leaves;
filicinophyta (often) have divided/pinnate leaves;
filicinophyta produce spores in sporangia/spores on the undersides of leaves;
filicinophyta exhibit alternation of generations;
filicinophyta have primitive vascular tissue / no true xylem and phloem;
coniferophyta have woody stems;
coniferophyta (often) have narrow leaves/needles/scales;
coniferophyta produce seeds in cones/unenclosed seeds;
angiospermophyta have flowers;
angiospermophyta have ovules in ovaries;
angiospermophyta produce seeds (with hard coats) in fruits;
(9)
(b)
Plants store carbohydrate in the form of starch. Explain the reasons for starch being
digested by the human digestive system.
starch is a large molecule;
large molecules/starch cannot be absorbed by the intestine/villi/epithelial
cells;
glucose produced by digestion of starch can be absorbed;
starch/glucose is a useful source of energy;
starch is not used in humans;
glucose is stored as glycogen not starch;
starch is not soluble/could not be transported by blood; ben2733boards22top
(4)
(c)
Compare the structure of prokaryotic and eukaryotic cells.
Prokaryotic cells
Eukaryotic cells
no nucleus
nucleus;
naked DNA
DNA associated with histone/protein;
loop of DNA
strands of DNA;
no mitochondria
mitochondria;
70S/ smaller ribosomes
80S/ larger ribosomes;
no/few internal membranes / no
organelles
internal membranes/organelles/
Golgi/ER/lysosomes;
smaller in size (approx. 1-10µm)
larger in size (approx. 10-100µm);
cell wall (glycoprotein) present
sometimes present/not in animal cells;
(5)
(Total 20 marks)
41.
Up to two additional marks are available for the construction of your answers.
(2)
(a)
Describe the movement of energy and nutrients in an ecosystem.
ecosystem is a community and its abiotic environment;
solar energy collected by autotrophs/plants (via photosynthesis);
moves through trophic levels via food;
only 5 to 20% transferred from one trophic level to next / never
IB Questionbank Biology
29
100% efficient;
lost as metabolic heat/organic waste;
energy flow can be illustrated by pyramid shape;
organisms absorb nutrients from food/environment;
nutrients occur as complex organic matter in living organisms;
after death, saprotrophic bacteria and fungi (decomposers) breakdown
complex organic matter;
breakdown products are simpler substances;
absorbed into plants for resynthesis into complex organic matter/recycled
(6)
(b)
Explain how sexual reproduction can eventually lead to evolution in offspring.
offspring vary in traits; variation results from sexual reproduction;
independent assortment of alleles (during meiosis of spermatogenesis/
oogenesis) contributes to variation; meiosis is the cellular process that produces gametes;
crossing over (during meiosis) increases variation; fertilization (combination of different
genomes) contributes to variation; more offspring may be produced than the environment can
hold; struggle for existence can occur; offspring whose traits best adapt them to environment
will survive/survival of fittest; change in environment will lead to survivors with new/different
traits; correct use of term natural selection/selective pressure; variation is heritable / over time
more offspring born with new trait; change in gene pool; when entire population (of a species)
exhibits new trait, evolution has occurred
(8)
(c)
Using simple external recognition features, distinguish between the plant phyla bryophyta
and angiospermophyta.
bryophyta
angiospermophyta
nonvascular/unspecialized tissue/no
veins
vascular/specialized
tissue/veins;
small/height up to 7 cm
tall/ height up to 100 m;
exist as organized masses of cells /
“leafy” appearance
contain water-conducting cells
(tissue)/food-conducting
tissue/support tissue;
reproductive structures / capsules
appear on stalks
have flowers;
microscopic spores
covered seeds/fruits;
sometimes hair-like extensions below
growing surface/rhizoids
roots;
(4)
(Total 20 marks)
42.
The element arsenic (As) is not needed for plant growth and development. The accumulation of
arsenic in the Chinese brake fern (Pteris vittata) was studied. Young ferns with five or six leaves
were transplanted to soil contaminated with arsenic and were grown for 20 weeks in a
greenhouse.
The graph below shows the arsenic concentrations in leaves and roots of the Chinese brake fern
–1
during the 20 weeks after transplanting. Arsenic concentration is expressed as mg As kg dry
weight of plant.
IB Questionbank Biology
30
[Used with permission, from Journal of Environmental Quality. 2002. Vol 31. Pp 1671–1675.]
IB Questionbank Biology
31
(a)
Using the data in the graph, describe the accumulation of arsenic in the Chinese brake
fern.
arsenic accumulates in leaves; arsenic concentration (in leaves) increases rapidly in the
first 7 weeks; arsenic (in leaves) increases from 0 to approximately
–1
–1
6000 mg kg at 7 weeks; maximum arsenic level (in leaves) is about 7500 mg kg
at end of experiment/valid numerical example; after week 7 arsenic concentration in
plant increases more slowly/begins to plateau; arsenic concentration in roots remains
relatively unchanged throughout the experiment;
(3)
The table below shows the total amount of arsenic accumulated by the Chinese brake fern,
expressed as a concentration in the plant tissue and as a percentage of the arsenic originally in
the soil.
Time / weeks
Arsenic concentration
–1
in fern / mg As kg
Percentage of original soil
arsenic absorbed by fern
0
2
0.00
2
66
0.05
4
221
0.15
6
408
0.28
8
1300
0.88
12
5390
3.68
16
13800
9.43
20
37900
25.90
[Adapted from Sinton, L W et al. 1999. Applied and Environmental Microbiology. Vol 65, issue 8. Pp 3605–3613.
Published by the American Society for Microbiology, 1752 N Street N.W., Washington, DC 20036, USA. Reproduced
with permission.]
(b)
(i)
Assuming the mean rate of arsenic accumulation over the first 20 weeks continued,
calculate how long it would take to remove all the arsenic from the soil.
77 weeks
(1)
(ii)
Using the data in the table, discuss the potential of using Chinese brake fern to
remove all arsenic from contaminated soil.
Chinese brake fern could be used to remove arsenic from soil;
after 20 weeks about 25% of soil arsenic removed by fern;
arsenic concentration increases (rapidly) in fern (tissue) in 20 weeks;
eventually/longer periods may reach toxic levels for plant
(2)
(c)
Suggest one possible consequence of arsenic accumulation in plants for other organisms
in the community.
IB Questionbank Biology
32
plants may become toxic for consumers; arsenic may accumulate in the food chain /
biomagnification
(1)
(Total 7 marks)
43.
(a)
Outline three factors that affect plant distribution.
 plant distribution closely linked to levels of abiotic factors in the
environment
 given organism can survive only within a certain temperature range to
which it is adapted
 water is a limiting factor in most terrestrial ecosystems and plants are
classified according to ability to tolerate water shortage
 most plants can only tolerate narrow pH range
 light intensity/quality/wavelength and duration/photoperiod are
important for photosynthesis
(3)
(b)
Outline a method used to correlate the distribution of plant species with an abiotic factor.
Transect used when there is a transition in habitats and populations; description of use of
a line or belt transect; height variation/light intensity/salinity/various abiotic factors can
be recorded; along the transect, along with sampling of plant species present
(2)
(Total 5 marks)
44.
(a)
State one example of the accidental release of an alien species that has had a significant
impact on an ecosystem.
zebra mussel (Dreissenapolymorpha originally from Russia/Caspian)
carried in ships’ ballast water and introduced into Great Lakes / rats
accidentally introduced to mainland of New Zealand from visiting
ships / Africanized honey bees introduced to Brazil (“killer bees”)
(1)
(b)
Discuss the impact of alien species on ecosystems.
Inter-specific competition/alien species have characteristics that may enable them to outcompete native species; lack of predators may allow alien species to reproduce more
rapidly; alien species may utilize areas or resources that native species cannot; predation
by invasive species can cause loss of biodiversity; can lead to species extinction,
especially of endangered species; alien species may introduce new diseases; use of alien
species for biological control can be ineffective or negative
(3)
(Total 4 marks)
45.
Describe the distribution of tundra in the world today.
tundra is found in the Northern hemisphere only; at latitudes of around 60°; size of tundra is
changing due to global warming
(Total 2 marks)
IB Questionbank Biology
33
46.
Invasion of alien species has become a serious issue in most environments of the world.
This study of Nordic environments charts the presence of alien species over the last century.
Relative proportions of invertebrates, vertebrates and plants and fungi are indicated in each bar.
[Reproduced with permission of the Nordic Council of Ministers.]
IB Questionbank Biology
34
(a)
(i)
State the ecosystem in which the proportion of alien vertebrates is the greatest.
Freshwater
(1)
(ii)
Describe the general pattern of the numbers of alien species in terrestrial and
marine ecosystems.
Increases exponentially
(1)
(b)
Suggest a reason why alien plant and fungi invasion is greatest in the terrestrial
ecosystem.
plants are purposely transported by people to new places for their use; the ecosystem is
changing/warming so new kinds of plants are now able to survive/compete with native
plants; only a few plants are aquatic so few would be expected in water; fungal
spores/seeds can travel more easily in air; terrestrial ecosystems provide more suitable
habitats
(1)
(c)
Identify how invasion of marine waters by alien invertebrates might occur.
Accidental transport of organisms (e.g. by vessels/boats); purposeful importation for
commercial reasons
(1)
(d)
Discuss the impact of alien species on ecosystems.
pros:
may control a pest species (in an ecosystem);
economic/social benefits e.g. reforestation to reduce soil erosion /
other reasonable examples;
cons:
competition reduces survival of native species;
upsets the balance between predators and prey;
leads to extinction of native species / reduces biodiversity;
(3)
(Total 7 marks)
47.
(a)
List four factors that affect the distribution of plant species.
pH of soil; water / humidity; light; temperature; salinity; mineral nutrients; competition;
altitude; pollinating agents; predators / parasites; slope
(4)
IB Questionbank Biology
35
(b)
Describe one effect of plants on an abiotic factor in a pioneer community.
adds humus to soil;breaks down rock (through roots, chemicals, rhizoids); holds
soil/prevents erosion; aerates soil; provides shade; reduces water content
(1)
(Total 5 marks)
48.
(a)
State the name of a statistical method used to quantify changes in biodiversity.
Simpson Diversity Index
(1)
(b)
Discuss reasons for conservation of biodiversity of a named ecosystem.
name of ecosystem:
e.g. (tropical) rainforest;
ethical reason:
every species has a right to life, regardless of whether it is useful/non
useful to humans;
potential of undiscovered medicines;
ecological reasons:
better use of the rainforest may occur by respecting the existing balance
in concert with the indigenous people;
native species are adapted to local conditions whereas invasive species
are less likely to be in balance;
species in the rainforest are interdependent so loss of species threatens
the rest of the community;
deforestation of rainforests increases soil erosion/silting of rivers/flooding/
CO2 atmospheric levels;
economic reasons:
ecotourism is a potential source of income;
aesthetic reasons:
loss of beauty of the system;
artists are inspired by the images/flowers/animals of rainforests;
heritage/cultural reasons:
maintenance of the rainforest preserves human cultural diversity;
(5)
(Total 6 marks)
49.
Population size is influenced by certain factors.
If I = immigration, E = emigration, N = natality, M = mortality and (N + M) = (I + E) = 0, which
phase is this population in?
A.
Exponential phase
B.
Transitional phase
C.
Plateau phase
IB Questionbank Biology
36
D.
Growth phase
(Total 1 mark)
50.
An animal has radial symmetry, a sac-like body with only one opening and tentacles with
stinging structures. To which phylum does this animal belong?
A.
Annelida
B.
Cnidaria
C.
Mollusca
D.
Porifera
(Total 1 mark)
51.
Which of the following is a consequence of global temperature rise on arctic ecosystems?
A.
Increased rates of decomposition of detritus trapped in permafrost
B.
Decrease of geographical range of habitats for temperate species
C.
Decrease of pest species and increase of permafrost species
D.
Increase of geographical range of habitats for permafrost species
(Total 1 mark)
52.
Which of the following is a characteristic of platyhelminthes?
A.
Many pairs of legs
B.
Flat body
C.
Hard exoskeleton
D.
Presence of cnidocytes
(Total 1 mark)
53.
During aerobic cell respiration, oxygen is consumed and carbon dioxide is produced inside
cells. This generates concentration gradients between respiring cells and the environment, which
cause diffusion of oxygen and carbon dioxide. Both oxygen and carbon dioxide are soluble in
water. As the temperature rises, water becomes saturated at a lower concentration of the gas.
Laternula elliptica is a mollusc that lives on the sea bed in Antarctica. Its body temperature is
always similar to that of the environment around it. To investigate the effect of temperature on
Laternula elliptica, specimens were kept in temperature-controlled aquaria. The oxygen
concentrations of water near the gills and in the body fluids were measured, at a range of
temperatures from 0°C to 9°C. The graph below shows the mean results.
IB Questionbank Biology
37
[With kind permission from Springer Science+Business Media and the author.]
(a)
(i)
Outline the relationship between temperature and oxygen concentration in the body
fluids in Laternula elliptica.
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)
(ii)
Suggest two reasons for the relationship.
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
(2)
(b)
In its natural environment, Laternula elliptica buries itself in the mud on the sea bed.
In this investigation, it was found that above 6°C it is unable to bury itself. Suggest a
reason for this.
not enough energy/ATP/aerobic respiration (for muscle contraction/movement)
(1)
IB Questionbank Biology
38
The world’s oceans can absorb large amounts of carbon dioxide. This process has been studied
in the Pacific Ocean near Hawaii, by measuring carbon dioxide concentrations in the
atmosphere and in surface water every month, from October 1988 onwards. The graph below
shows the carbon dioxide concentration expressed as partial pressures (Pco 2).
[Source: Nature by Nature Publishing Group. Reproduced with permission of Nature Publishing Group in the format
Journal via Copyright Clearance Centre.]
(c)
(i)
Describe the trends in atmospheric carbon dioxide concentration, shown in the
graph.
rising trend overall; annual rise and fall / fluctuations
(2)
(ii)
Suggest two reasons for the trends that you have described.
(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)
IB Questionbank Biology
39
(d)
(i)
Diffusion of carbon dioxide only occurs when there is a concentration gradient.
Deduce the pattern of carbon dioxide diffusion, between water and atmosphere,
from 1988 to 2002.
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)
(ii)
The graph provides evidence for the hypothesis that there will be no net diffusion
of carbon dioxide between water and atmosphere by 2020. Explain this evidence.
(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)
The concentration of carbon dioxide in the atmosphere is currently 385 ppm (parts per million).
Variations in the concentration of carbon dioxide in the atmosphere can be studied using icecores. An ice-core record covering the last 400 000 years has been obtained from Vostok in the
Antarctic. The graph below shows the carbon dioxide concentrations that were measured at
different depths in the ice. Atmospheric temperatures are also shown on the graph. These were
deduced from ratios of oxygen isotopes. The upper line on the graph shows CO 2 concentrations
and the lower line shows temperature.
[Source: Nature by Nature Publishing Group. Reproduced with permission of Nature Publishing Group in the format
Journal via Copyright Clearance Centre.]
(e)
(i)
State the highest carbon dioxide concentration shown on the graph.
300 ppm
(1)
IB Questionbank Biology
40
(ii)
State the highest temperature shown on the graph.
3.3°C
(1)
(f)
Using the data in the graph, deduce the relationship between atmospheric carbon dioxide
concentration and temperature.
positive correlation / higher temperature with higher CO 2 concentration
(1)
(g)
Using the data in this question, explain reasons for concern about the long-term survival
of Antarctic species, such as Laternula elliptica.
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
(3)
(Total 18 marks)
54.
The element arsenic (As) is not needed for plant growth and development. The accumulation of
arsenic in the Chinese brake fern (Pteris vittata) was studied. Young ferns with five or six leaves
were transplanted to soil contaminated with arsenic and were grown for 20 weeks in a
greenhouse.
The graph below shows the arsenic concentrations in leaves and roots of the Chinese brake fern
–1
during the 20 weeks after transplanting. Arsenic concentration is expressed as mg As kg dry
weight of plant.
IB Questionbank Biology
41
[Used with permission, from Journal of Environmental Quality. 2002. Vol 31. Pp 1671–1675.]
(a)
Using the data in the graph, describe the accumulation of arsenic in the Chinese brake
fern
arsenic accumulates in leaves; arsenic concentration (in leaves) increases rapidly in the
first 7 weeks; arsenic (in leaves) increases from 0 to approximately
–1
–1
6000 mg kg at 7 weeks; maximum arsenic level (in leaves) is about 7500 mg kg at end
of
experiment / valid numerical example; after week 7 arsenic concentration in plant
increases more slowly/ begins to plateau; arsenic concentration in roots remains
relatively unchanged throughout the experiment
(3)
The table below shows the total amount of arsenic accumulated by the Chinese brake fern,
expressed as a concentration in the plant tissue and as a percentage of the arsenic originally in
the soil.
Time / weeks
IB Questionbank Biology
Arsenic concentration
–1
in fern / mg As kg
Percentage of original soil
arsenic absorbed by fern
0
2
0.00
2
66
0.05
4
221
0.15
6
408
0.28
8
1300
0.88
12
5390
3.68
16
13800
9.43
20
37900
25.90
42
[Adapted from Sinton, L W et al. 1999. Applied and Environmental Microbiology. Vol 65, issue 8. Pp 3605–3613.
Published by the American Society for Microbiology, 1752 N Street N.W., Washington, DC 20036, USA.
(b)
(i)
Assuming the mean rate of arsenic accumulation over the first 20 weeks continued,
calculate how long it would take to remove all the arsenic from the soil.
77 weeks
(1)
(ii)
Using the data in the table, discuss the potential of using Chinese brake fern to
remove arsenic from contaminated soil.
Chinese brake fern could be used to remove arsenic from soil;
after 20 weeks about 25% of soil arsenic removed by fern;
arsenic concentration increases (rapidly) in fern (tissue)
in 20 weeks;
eventually/longer periods may reach toxic levels for plant
(2)
(c)
Suggest one possible consequence of arsenic accumulation in plants for other organisms
in the community.
plants may become toxic for consumers; arsenic may accumulate in the food chain /
biomagnification
(1)
(Total 7 marks)
55.
The following figure represents a terrestrial food web.
IB Questionbank Biology
43
(a)
Identify the trophic level of the toad.
tertiary consumer / fourth trophic level
(1)
(b)
Outline a method that could be used to estimate the population of rabbits in this
environment.
capture–mark–release–recapture method;
marked unit area;
apply a paint spot/ear tag/leg ring/radio transmitter to the captured rabbits;
sufficient time must elapse to allow mixing of population to occur;
second capture must be from same marked area;
n1  n 2
calculate the Lincoln index / population size = n3 ;
n1 = first capture, n2 = second capture, n3 = number marked in
second capture
(4)
(c)
The Simpson diversity index is used to calculate the species richness in an ecosystem.
N ( N  1)
D=
 n(n  1)
Define the terms N and n in the formula above.
N = total number of organisms of all species found
n = number of individuals of a particular species/per species
(2)
(Total 7 marks)
56.
Evaluate the use of indicator species in monitoring environmental changes.
indicator species sensitive to/need specific environmental conditions to survive;
monitor population size of indicator species over time;
biotic index can be calculated;
low overall score when abundance of tolerant species / lack of indicator
species / vice versa;
represent summation of factors/overall assessment of environmental conditions;
time consuming / species not easy to identify (need keys) / species may not be
present for other reasons such as season / another disadvantage;
methodology is simple / minimum equipment needed;
needs a reference study/guide to compare;
example of variable e.g. oxygen level / temperature / heavy metals / sulphur
dioxide in air / other;
example of appropriate indicator species e.g.Tubifexto heavy metals /
Chironomis to low oxygen levels / lichens to sulphur dioxide / other
(Total 6 marks)
57.
(a)
Distinguish between fundamental niches and realized niches.
IB Questionbank Biology
44
a niche is the place where an organism lives and the roles that it plays in
its habitat;
fundamental niche of a species is the potential mode of existence while
realized niche of a species is the actual mode of existence;
fundamental niche depends on species’ adaptations while the realized
niche also depends on competition with other species
(2)
(b)
Outline the changes in species diversity and production during primary succession.
one/few species/lichens/moss at the start;
pioneer community slowly increases in species diversity;
production gradually increases as more soil develops/better conditions/
more diversity
(2)
(c)
Outline, using examples, the biogeographical features of nature reserves that promote the
conservation of diversity.
size; edge effect; example of edge effect; habitat corridor; example of habitat corridor;
habitat/niche diversity; human management;
e.g. size:
large reserves usually promote diversity more effectively than small ones;
edge effect:
cause different ecology of central areas compared to edges;
example of edge effect:
cowbird lays eggs in nests of other birds near edges of forests / fragmentation
of forests increased cowbirds as more edges;
habitat corridor:
permit organisms to move between different parts of a fragmented habitat;
example of habitat corridor:
tunnels under roads;
habitat/niche diversity:
functioning reserve requires a diversity of niches to support the ecosystem
structure;
human management:
banning hunting/lumbering/petroleum exploitation;
(3)
(Total 7 marks)
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58.
Discuss international measures that would promote the conservation of fish.
require international agreement/cooperation; difficulties of enforcing agreements / to determine
maximum sustainable yield / to obtain and interpret data / monitor populations/stocks;
economic consequences for livelihood of fishermen/associated trades; total ban on fishing in
threatened areas/endangered species/exclusion zones; limiting size of fish caught / limits on size
of net mesh / ban on drift nets / indiscriminate in species of fish caught; limiting size to total
allowable catch/quotas; limiting fishing to non-productive periods of fish / closed seasons
banning fishing during breeding season; reducing fishing days at sea / fixing number and type
of vessels authorized to fish; regulation on pollution of bodies of water; use of fish farms
(Total 6 marks)
59.
This question is about the food web below
What is the energy transfer level from the kangaroo rat to the weasel shown in the food web
above?
A.
Three times greater than the energy transfer from the roadrunner to the bobcat
B.
Half the energy transfer from chaparral plants to the meadow mouse
C.
A quarter of the energy transfer from the quail to the bobcat
D.
Approximately the same as the energy transfer from the meadow mouse to the opossum
(Total 1 mark)
60.
What features distinguish Platyhelminthes from Annelida?
Platyhelminthes
A.
segmented body
IB Questionbank Biology
Annelida
non-segmented body
46
B.
non-segmented body
segmented body
C.
bilateral symmetry
no bilateral symmetry
D.
no bilateral symmetry
bilateral symmetry
(Total 1 mark)
61.
(a)
Distinguish between fundamental niches and realized niches.
fundamental niche is the potential mode of existence whereas realized niche
is the actual mode of existence; adaption/competition/predation/powers of distribution
are important in determining the realized niche;
(2)
(b)
Describe a primary succession in a named type of habitat.
named type of habitat; (e.g. land left after lava flow/glacier retreat /
sand dune)
primary succession occurs on bare/lifeless substrate;
organisms move into an area and change its nature/pioneers colonize;
pioneers are simple autotrophs; (e.g. lichens grow first)
break down substrate; (e.g. to form organic soil)
leads to an eventual climax ecosystem; (e.g. forest)
stages in the succession follow a set sequence
(3)
(Total 5 marks)
62.
(a)
Label the levels of the trophic pyramid of energy shown below.
Tertiary Consumer
Secondary Consumer
Producer
(3)
(b)
Discuss the impact of alien species on the environment.
(interspecific) competition with native species;
does not have natural predators so may survive more;
can be a predator difficult to control;
reproduce faster/more;
may cause the extinction of native species;
most are benign/some may be beneficial (e.g. honeybee introduced
to the Americas from Europe in the 1600s)
(3)
(Total 6 marks)
63.
Which taxa do Zerynthia rumina and Zerynthia polyxena share?
A.
They share the same class but not the same family.
B.
They share the same species but not the same class.
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47
C.
They share the same class but not the same genus.
D.
They share the same family but not the same species.
(Total 1 mark)
64.
Up to two additional marks are available for the construction of your answers.
(2)
(a) Draw a labelled graph showing a sigmoid (S-shaped) population growth curve.
(4)
(b)
Describe what is meant by a food chain and a food web.
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)
(c)
Explain the relationship between rises in concentration of atmospheric gases and the
enhanced greenhouse effect
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)
(Total 20 marks)
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65.
Many factors affect the distribution of animal species including weather patterns. The mosquito
Anopheles is a carrier of malaria, a disease that kills one to two million people annually. The
eggs of the mosquito are laid in water and they hatch out as larvae before turning into adult
mosquitoes. A study was undertaken to look at the influence of weather patterns on the
incidence of bites on children. Being bitten increases the risk of catching malaria.
The graphs show human biting rates (HBR) by Anopheles gambiae and Anopheles funestus and
precipitation over the study period.
[Adapted from J A Patz et al. 1998. “Predicting key malaria transmission factors, biting and entomological
inoculation rates, using modelled soil moisture in Kenya.” Tropical Medicine and International Health. Vol 3. Pp
818–827. Reproduced with permission from Wiley.]
(a)
State the week number when the highest human biting rate (HBR) is found for
A. gambiae.
..........107/108.....................................................................................................
(1)
(b)
Calculate the difference in peak HBR for A. gambiae and A. funestus for week 6.
35
(1)
(c)
Evaluate the effect of increased precipitation on HBR for both species.
both species show relationship between elevated precipitation and higher HBR (e.g. between
week 0 and week 8 / week 100 and week 108); there is a lag between the period of precipitation and
IB Questionbank Biology
49
the increase in HBR; sometimes elevated precipitation does not lead to peaks of HBR (e.g. week 27);
precipitation has a greater effect on Anopheles gambiae/A. gambiae;
(3)
(d)
Suggest how predictions of global climate changes, such as predictions of precipitation
patterns, could be used to help control malaria.
spraying insecticides just before rainy seasons; draining swamps before (and after) rain;
providing (endangered) population with repellents/mosquito nets before rainy
season
(1)
(e)
Suggest another factor which might affect the ecological distribution of mosquitoes.
temperature / breeding site / food supply / predators /
(1)
(f)
Suggest a biological control that might be introduced to reduce HBR.
using natural predators of mosquitoes; using natural pathogens of mosquitoes;
introduction of sterile males; setting traps baited with mosquito
pheromones/hormones
(1)
(Total 8 marks)
66.
(a) Earthworms are primary consumers that can be grown on household food waste such
as fruit and salad leftovers. Outline their potential as an energy-containing food source for
humans.
much loss of energy / 80–90% loss of energy; low down food chain so efficient; loss of
energy through respiration/heat; loss of energy through egestion; less valuable as
a food source than primary producers; converts undigestible material into
digestible materials
(3)
(b)
State the units used in a pyramid of energy.
kJ m–2 yr–1 / kilojoules per meter squared per year
(1)
(c)
Describe the effects of ultraviolet radiation on living tissues.
ultraviolet/UV light penetrates tissues; damages DNA / causes gene mutation; can lead to
uncontrolled cell division/mitosis; stimulates the production of vitamin D;
stimulates the synthesis of pigments/melanin; can cause skin cancer / cataracts;
affects photosynthesis
(2)
(Total 6 marks)
67.
Discuss the role of ex situ conservation of endangered species.
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(e.g. zoo/botanic garden/seed bank/aquarium/laboratory) / definition of ex situ;
advantages: [3 max] prevent extinction / help in conservation of species; possible breeding;
reintroduction into the wild; correct nutrition constantly; veterinary care; educational
use / research use; prevent poaching/picking rare flowers/damage to habitat by man;
disadvantages: [2 max] difficulty in the reintroduction of the species to the wild; increases
inbreeding / restricted gene pool; selection of organisms to be kept ex situ; not their
natural habitat / reduces evolution; does not solve the cause/problem e.g. habitat loss;
(Total 6 marks)
68.
What conclusion can be made from the following evidence from an analysis of DNA fragments?
A.
Both children are related to both parents.
B.
Child I is related to the man but child II is not.
C.
Both children are unrelated to either of the parents.
D.
Child II is related to the man but child I is not.
(Total 1 mark)
69.
The following diagram shows part of a food web from Yellowstone Park.
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What would be the short-term effects on the populations of the other species if the gray wolf
were exterminated?
Beaver
Moose
Elk
Aspen
A.
Increase
Decrease
Increase
Increase
B.
Decrease
Decrease
Decrease
Decrease
C.
Increase
Increase
Decrease
Increase
D.
Decrease
Increase
Increase
Decrease
(Total 1 mark)
70.
Slime moulds (Acrasiomycota) are protoctists. They feed on decaying organic matter, bacteria
and protozoa.
Which of the terms describes their nutrition?
I.
Detritivore
II.
Autotroph
III.
Heterotroph
A.
I only
B.
I and II only
C.
I and III only
D.
I, II and III
(Total 1 mark)
71.
Why do food chains in an ecosystem rarely contain more than five organisms?
A.
Nutrients are recycled by the decomposers back to the producers.
B.
Nutrients are lost from the ecosystem when organisms die.
C.
The conversion of food into growth by an organism is not very efficient.
D.
Energy is recycled by the decomposers back to the producers.
(Total 1 mark)
72.
Several greenhouse gases occur in the atmosphere. Carbon dioxide (CO 2) is one of them but so
are methane (CH4) and oxides of nitrogen (NOx).
Why are oxides of nitrogen classed as greenhouse gases?
A.
They trap some of the long-wave radiation emitted by the Earth’s surface.
B.
They prevent short-wave radiation from reaching the Earth’s surface.
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52
C.
They dissolve in rainwater to produce acid rain.
D.
They are only produced by human activity whereas CO 2 and CH4 are also produced
naturally.
(Total 1 mark)
73.
Population growth, as shown by the curve below, is the result of changes in mortality, natality,
immigration and emigration. Which of the following statements about population growth is
correct?
A.
In phase I there is no mortality.
B.
In phase II mortality equals natality and immigration equals emigration.
C.
In phase II mortality and emigration are less than natality and immigration.
D.
In phase III mortality and emigration are less than natality and immigration.
(Total 1 mark)
74.
Which of the organisms A–D, identified by the key below, represents an Annelid?
1. Shows bilateral symmetry
Does not show bilateral symmetry
go to 2
Cnidaria
2. Has a segmented body
Does not have a segmented body
go to 3
go to 4
3. Has jointed legs
Does not have jointed legs
A
B
4. Has a shell
Does not have a shell
C
D
(Total 1 mark)
75.
To which group do sponges belong?
A.
Cnidaria
B.
Filicinophyta
C.
Porifera
D.
Mollusca
(Total 1 mark)
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76.
The diagram below shows a population growth curve.
*sorry couldnt
find the pic :/
At which time in the population growth curve does the population size begin to decline?
A.
Between the time marked 1 and 2
B.
During the time marked 2
C.
Between the time marked 2 and 3
D.
The graph does not show a time when population size declines
(Total 1 mark)
77.
The graph below shows variation in the concentration of CO2 in the atmosphere as measured at
Mauna Loa in Hawai’i. The small inset graph shows the variations in CO 2 during a one year
period.
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[Source: adapted from Dr P Tans, NOAA Earth System Research Laboratory]
Why does the amount of CO2 fall between April and August?
A.
Seasonal increase in the rate of photosynthesis in the northern hemisphere forests
B.
Seasonal decrease in the rate of photosynthesis in the northern hemisphere forests
C.
Seasonal decrease in the rate of fossil fuel consumption
D.
Seasonal increase in the amount of CO2 dissolved in the oceans
(Total 1 mark)
78.
The scarlet cup fungus (Sarcoscypha coccinea) obtains its nutrition from decaying wood by
releasing digestive enzymes into the wood and absorbing the digested products.
Which of the following terms describe(s) the fungus?
I.
Autotroph
II.
Heterotroph
III.
Saprotroph
A.
III only
B.
II and III only
C.
I and III only
D.
I, II and III
(Total 1 mark)
79.
Below is a graph of atmospheric CO2 levels measured at Mauna Loa Observatory, Hawai’i.
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[Source: adapted from Dr P Tans, NOAA Earth System Research Laboratory]
a)
Explain the observed changes in atmospheric CO2 concentration from 1960 to 2005.
(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)
(b)
Outline the precautionary principle.
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)
(Total 5 marks)
80.
(a) Define the terms species, population and community.
species: group of organisms that can interbreed to produce fertile offspring;
population: group of organisms of the same species living in the same area at the same
time;
community: group of populations living and interacting with each other in an area
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(3)
(b)
Explain the shape of the pyramids of energy that are constructed by ecologists to
represent energy flow in an ecosystem.
energy flows up from one trophic level to the next (in a community); energy is lost at each
stage by waste products/feces/not all the organism is consumed; most
energy is lost through respiration/heat; each level on the pyramid is
about 10%–20% of the size of the one below it / 80%–90% energy lost
between levels; labelled diagram of pyramid of energy (indicating
trophic levels)
(3)
(Total 6 marks)
81.
Up to two additional marks are available for the construction of your answers.
(2)
(a) Draw a labelled diagram showing the ultrastructure of a typical prokaryote.
INCLUDE: cell wall — a uniformly thick wall; pili — hair-like structures / flagellum — at least
length of the cell; 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;
(4)
(b)
Outline how three different environmental conditions can affect the rate of
photosynthesis in plants.
light: rate increases with increasing light; it reaches maximum then plateaus; as all chloroplast
molecules are working at optimal pace;
temperature: 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: rate increases with increasing carbon dioxide level; it reaches maximum then
plateaus; as photosynthesis operating at optimal level
(6)
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(c)
Explain how the emission of gases, both naturally and through human activity, can alter
the surface temperature of the Earth.
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)
(Total 20 marks)
82.
(a) Discuss the impact of an alien species on an ecosystem.
1) Interspecific competition (competition between species). Example: the floating fern
has damaged many lakes in the tropics and subtropics; grows fast, covers the
water surface and eliminate native species. It has been controlled by introducing
another alien species: salvinia weevil which feeds on the floating fern (biological
control).
2) Species extinction. Example: three species of rats introduced on the mainland of New
Zealand causing many species of birds to disappear.
3) Predation. Example: one Island that remained rat-free in New Zealand, Big South
Cape Island, was home for many rare birds until the rats finally reached it. They
grew exponentially, attacked eggs, young birds and even adult birds - two species
of birds went extinct, however a third was saved by human intervention and
relocated on another island that was rat-free.
e.g. Cane toad introduction to Australia; (Accept rats to New Zealand, etc.) impact on
specified ecosystem; competes with local toads/frogs to displace them; poisons
local mammals;
(3)
(b)
Outline the temperature and vegetation characteristics of one major biome.
correctly named biome e.g. temperate deciduous forest; temperature range / e.g.
warm/15–18°C summers and cold/3–7°C winters / significant annual temperature
variation; dominant plant/ecosystem characteristics e.g. dominant plants are
broad leaf trees (that lose leaves annually) / significant diversity of understanding
plants;
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(2)
(Total 5 marks)
83.
(a) Define biomass.
the total dry organic matter of living organisms/ecosystems
(1)
(b)
Describe how biomass may be measured.
organism/sample is cleaned of any other material (e.g. plant is pulled free of soil and
roots washed); measure wet mass of organism/sample; organism/sample is dried in
an incubator/drying oven to constant mass; biomass calculated based on wet mass
of sample
(2)
(c)
Explain the biomass change in different trophic levels.
biomass is largest in lowest trophic level / lowest in highest trophic levels / decreases
from lower to higher trophic levels; only 10–20% organic material/biomass passes
up each trophic level; organic material used for respiration / activity / lost as heat
(you should probably include an example)
(3)
(Total 6 marks)
84.
(a) Define the terms gross production and net production.
gross production: amount of organic matter/biomass produced by plants / plant
respiration and net production;
net production: amount of gross production of an ecosystem remaining after subtracting
the amount used in respiration/gross production — respiration
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(2)
(b)
Using the table below, compare the characteristics of the following biomes.
Biome
Desert
Tropical rainforest
Tundra
Characteristic of
vegetation
Temperature
Moisture
high temperature/
thermal amplitude
in day and cold at
night
dry / average rainfall
less than 25 cm
year^–1
xerophytes / succulent/
sparse low lying
bushes adapted to
water conservation;
hot
damp / wet / average
rainfall 225 cm
year^–1
epiphytes / trees and
wide leaf plants in
undergrowth / huge
diversity / tall mature
trees of many species;
cold / –6°C to –
12°C
dry / average rainfall
25 cm year^–1
small and close to
ground / red leaves /
grasslands with a few
small trees;
(3)
(Total 5 marks)
85.
(a) (i)
State one example of a deliberate release of an alien species,
including the name of the organism and where it was released.
e.g. beaver/castor liberated in Tierra del Fuego (you need a named example and a location)
(1)
(ii)
Using the example from (a)(i), outline the reason for its release and the impact it
had on the environment.
reason for release; impact on environment;
e.g. for hunting/fur; but built dams which altered river courses
(2)
(b)
Explain, using a named example, the cause and consequence of biomagnification.
named example; definition of biomagnification; cause; consequence;
e.g. name: DDT / pesticide to control mosquitoes of malaria; definition of
biomagnification: chemicals accumulate along the food chain; cause: as fat
soluble, it accumulates in fatty tissue; consequence: becoming more concentrated
at each trophic level / increasingly more toxic / ultimately leading to death of
organism up in food chain
(3)
(Total 6 marks)
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86.
The graph below shows variation in the concentration of CO2 in the atmosphere as measured at
Mauna Loa in Hawai’i. The small inset graph shows the variations in CO 2 during a one year
period.
[Source: adapted from Dr P Tans, NOAA Earth System Research Laboratory]
Why does the amount of CO2 fall between April and August?
A.
Seasonal increase in the rate of photosynthesis in the northern hemisphere forests
B.
Seasonal decrease in the rate of photosynthesis in the northern hemisphere forests
C.
Seasonal decrease in the rate of fossil fuel consumption
D.
Seasonal increase in the amount of CO2 dissolved in the oceans
(Total 1 mark)
87.
The scarlet cup fungus (Sarcoscypha coccinea) obtains its nutrition from decaying wood by
releasing digestive enzymes into the wood and absorbing the digested products.
Which of the following terms describe(s) the fungus?
I.
Autotroph
II.
Heterotroph
III.
Saprotroph
A.
III only
B.
II and III only
C.
I and III only
D.
I, II and III
(Total 1 mark)
88.
(a) Define biomass.
the total dry mass of organic matter in living organisms/ecosystems
(1)
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61
(b)
Outline the effects of ultraviolet (UV) radiation on living tissues.
UV radiation may cause damage to nucleic acids/proteins/lipids; give rise to increase in
skin cancer rates/glaucoma/cataracts/skin ageing; may negatively affect
plant/phytoplankton productivity; small amount beneficial e.g. vitamin D
synthesis; used to kill microbes/water purification; used to treat jaundice in
newborn infants
(2)
(Total 3 marks)
89.
(a) Describe the causes and consequences of a named example of biomagnification.
biomagnification is a process in which chemical substances become more concentrated at
each trophic level; certain toxins will accumulate in the body; fat soluble toxins
have a longer half life/will accumulate in body tissues; examples are:
DDT/TBT/organophosphates/mercury/other; effects of toxins can be magnified up
the food chain; top predators/consumers/carnivores have highest concentrations
stored in their body; For named example include: source of toxin e.g. TBT antifouling paint used on ships; how it enters food chain e.g. taken up by filter feeders;
links in food chain; effect on top consumer; ecosystem/community affected
(5)
(b)
Discuss conditions that favour K-strategies.
K-strategists require more resources; are long-lived; are large, therefore need large
habitats; slow maturation, therefore require longer protection from predators;
more care for offspring / small number of offspring; require stable habitat; usually
have stable population size; perform better in an environment with high levels of
competition/ no vacant niches; examples are: elephants / parrots / whales / Arctic
tern / tortoise / other correct example
(5)
(Total 10 marks)
90.
Seasonal changes of heterotrophic plankton biomass were measured in the western arctic Pacific
during a one year period. The mesozooplankton, whose size is greater than 330 μm, was formed
mainly by copepods. The microzooplankton, ranging from 10 to 200 μm, comprised mainly of
ciliates and flagellates. Heterotrophic nanoflagellates (HNF), size range 2 to 10 μm, are
organisms that feed on small flagellates and bacteria. The results are shown below.
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[Shinada, A et al. 2001. “Seasonal dynamics of planktonic food chain in the Oyashio region, western subarctic
Pacific”. Journal of Plankton Research. Vol 23, issue 11. Pp 1237–1248. © Oxford University Press. Reproduced
with permission.]
(a)
State the biomass of HNF found in this region in summer.
40 mg (carbon) m–3
(1)
(b)
Calculate the percentage increase in mesozooplankton from summer to spring. Show your
working.
367%
(2)
(c)
Suggest how the seasonal changes cause the differences in biomass of heterotrophic
plankton.
warmer temperatures (in summer/spring) cause enzyme activation / converse; more reproduction of
organisms (so more food) / converse; (more sun) more photosynthesis so more biomass (of
autotrophs) (so more food for organisms); in summer there are other organisms that feed on them;
ocean water movement could carry nutrients; seasonal changes in the abundance of food causes
difference
(3)
(Total 6 marks)
91.
(a) Outline the major differences in temperature and moisture that are characteristic of
two named biomes.
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(2)
(b)
Explain, using a named example, the cause and consequence of biomagnification.
definition of biomagnification; cause; consequence;
e.g. name: DDT / pesticide to control mosquitoes of malaria; definition of
biomagnification: chemicals accumulate along the food chain; cause: as fat
soluble, it accumulates in fatty tissue; consequence: becoming more concentrated
at each trophic level / increasingly more toxic / ultimately leading to death of
organism up in food chain;3
(3)
(Total 5 marks)
92.
(a) Outline the use of two named ex situ conservation measures.
Example 1: zoos; captive breeding of animals / permits assisted reproductive methods /
use of modern technology;
example 2: name: botanic gardens; allows for protected growth of plants / protected from
extreme climatic conditions / provision of all necessary conditions;
(4)
(b)
Discuss the environmental conditions that favour r-strategies and K-strategies.
K-strategies involve longer life-span, late maturity / likely to involve parental care, the
production of few offspring, and reproducing more than once; most organisms
have life histories that are intermediate; in unstable environment r-strategies
efficient;
better to produce as many offspring as quickly as possible; r-strategies favoured when
ecological disruption/in primary communities (in succession); such as pathogens
and pest species; K-strategies efficient in stable environment / maximizes fitness/in
climax communities; pays to invest resources in long-term development and long
life; some populations (e.g. Drosophila) switch strategies depending on
environmental conditions;
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(5)
(Total 9 marks)
93.
Zoophobas morio is an insect. Its larvae feed on bat feces in caves in Guatemala. What type of
organism is a Zoophobas morio larva?
A.
Autotroph
B.
Consumer
C.
Detritivore
D.
Saprotroph
(Total 1 mark)
94.
The diagram below shows some of the links in the carbon cycle.
What processes are taking place at I, II and III?
I
II
III
A.
photosynthesis
fossilization
combustion
B.
cell respiration
fossilization
greenhouse effect
C.
photosynthesis
decomposition
combustion
D.
cell respiration
decomposition
greenhouse effect
(Total 1 mark)
95.
Global warming threatens the survival of Arctic foxes. Which of the following factors could be
involved?
A.
I.
Competition with other fox species spreading north
II.
Reduction in numbers of prey species of Arctic foxes
III.
Decrease in oxygen availability to Arctic foxes
I only
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B.
I and II only
C.
II and III only
D.
I, II and III
(Total 1 mark)
96.
Which graph shows the sigmoid population growth curve?
(Total 1 mark)
97.
Ants, bees and wasps are classified in the same order. What can be deduced about these
animals?
A.
They are classified in the same class.
B.
They are classified in different phyla.
C.
They are classified in the same family.
D.
They are classified in different kingdoms.
(Total 1 mark)
98.
Pseudolarix amabilis produces seeds but not flowers. Physcomitrella patens has leaves but not
roots.
To which groups do they belong?
Pseudolarix amabilis
Physcomitrella patens
A.
coniferophyta
filicinophyta
B.
filicinophyta
angiospermophyta
C.
coniferophyta
bryophyta
D.
angiospermophyta
coniferophyta
(Total 1 mark)
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99.
Limpets are small animals that feed on the green algae which grow on rocks on seashores.
Oystercatchers (Haematopus bachmani) are birds that feed on limpets.
In a study on the north-west coast of the USA, where three limpet species are common (Lottia
digitalis, Lottia pelta and Lottia strigatella), the limpets were protected from the oystercatchers
by large wire cages. After two years the number of limpets in this area was compared with the
number of limpets in an area without cages, where oystercatchers were present.
[Source: Wooton, J T. 1992. “Indirect effects, prey susceptibility, and habitat selection: impacts of birds on limpets
and algae”. Ecology. Vol 73. Pp 981–991. Copyright by the Ecological Society of America.]
(a)
State the effect that the exclusion of the oystercatchers had on the total number of limpets
per m2.
Total number of limpets increased
(b)
Construct a food web to show the feeding relationship between the three species of
limpets, the oystercatchers and the green algae.
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(c)
Suggest reasons for the difference in numbers of L. strigatella between the areas where
oystercatchers were present and where oystercatchers were excluded.
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);
There is evidence to show that both air and water temperatures have increased over a period of
time. An investigation was undertaken to determine the effect this change in climate had on the
populations of another species of limpet, Patella depressa, around south-west England.
The population of the limpet was recorded in many locations and around 30 years later, this
study was repeated. The chart below compares the population in each of the locations.
(d)
On the map above label one location,
(i)
with the letter X, where the limpet population was abundant in the 1950s and
occasional in the 1980s (1980–1984).
X at 4th location going anticlockwise from top right
(ii)
with the letter Y, where the limpet population was abundant in both the 1950s and
in the 1980s (1980–1984).
Y at 8th, 9th or 11th location going anticlockwise from top right
(e)
Outline, using the data, the overall trend in the limpet population from the 1950s to the
1980s (1980–1984).
(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;
(f)
Suggest two reasons for the change in limpet population between the 1950s and the 1980s
(1980–1984).
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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;
100. A colony of a marine diving bird, Brunnich’s guillemot (Uria lomvia), lives on the southern
limits of the Arctic on Coats Island. Brunnich’s guillemots feed principally on Arctic cod
(Arctogadus glacialis) which are characteristic of Arctic waters.
The graph shows the changes in ice cover on Coats Island over a period of 19 years.
(a)
(i)
Outline the changes in ice cover shown in the data above.
ice cover has decreased (slightly);
the data show much variability/fluctuates;
(ii)
Suggest one reason for the changes in ice cover.
warmer air/atmosphere/water temperatures/global warming
(bringing about more ice melt)
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At Coats Island, chick mass at 14 days was measured in most years between 1988 and 2002.
The scattergraph below shows the results, plotted against proportion of ice cover.
(b)
(i) Outline the relationship between ice cover and the mass of 14-day-old chicks
on Coats Island.
increase in summer ice cover has a positive effect on mass increase;
high proportion of ice cover has little effect / (slightly) negative
effect on chick mass/growth;
(ii)
Suggest reasons for the relationship.
changes in (water) temperature/climate change influence fish
populations / food available for chick growth;
changes in habitat affect chick growth / rearing of chicks;
(c)
Predict, with a reason, the change in the mass of chicks in the years ahead.
mass may go down as proportion of ice cover has decreased;
mass may increase as most recent data shown in (bar) graph shows
increasing proportion of ice area;
101.
(a) Outline one example of herbivory.
(2)
named example of herbivore;
named example of plant;
e.g. aphid
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rose
(b)
State the units used in a pyramid of energy.
kJ m–2 yr–1 / kilojoules per metre squared per year / example of energy
per unit area per time unit (must be metric units)
(1)
(c)
Explain the small biomass of organisms in higher trophic levels.
much loss of energy / 10/20% retained / 80/90% loss of energy;
respiration;
egestion;
less valuable as a food source than primary producers;
102.
(a) Discuss the impacts of a named alien species introduced as a biological control
measure.
named alien species e.g. western mosquitofish / small Indian mongoose /
rosy wolfsnail;
introduced for removal of pests;
competes with native species;
excessive predation on native species that do not have defences;
impacts industry such as tourism/harvesting of natural resources;
Accept other specific examples of effects.
(b)
Outline the effects of ultraviolet radiation on living tissues.
ultraviolet/UV light penetrates tissues;
damages DNA / causes gene mutation;
can lead to uncontrollable cell division;
can cause skin cancer;
103. How is energy passed from one trophic level to the next?
I.
Food
II.
Light
III.
Heat
A.
I only
B.
I and II only
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C.
II and III only
D.
I, II and III
(Total 1 mark)
104. Up to two additional marks are available for the construction of your answers.
(2)
(a) Draw a labelled sigmoid population growth curve.
(4)
(b)
Outline the process of spermatogenesis in humans.
(5)
production of sperm/spermatozoa in the testes/seminiferous tubules;
first stage of sperm production requires divisions by mitosis;
cells then undergo a period of growth;
future sperm cells then undergo two meiotic divisions;
cells then differentiate to form sperm cells;
nourished by Sertoli cells
number becomes haploid / chromosome number halved / 46 to
23 chromosomes;
(c)
Explain the structure and function of the placenta during pregnancy.
embryonic/disc shaped structure that nourishes the developing embryo;
starts forming at implantation of the blastocyst/embryo;
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embryonic tissue invades/grows into the uterine wall;
fetal capillaries exchange material with maternal blood/lacunae;
allows exchange of food/oxygen/antibodies from mother’s blood to fetus;
allows exchange of carbon dioxide/waste products from fetal blood to mother;
connected to the embryo/fetus by an umbilical cord;
placenta takes over hormonal role of ovary;
indication of time this happens / at approximately 12 weeks;
secretes estrogen/progesterone;
hormone secretion maintains pregnancy;
expelled from uterus after childbirth;
105.(a)(i) Define biomagnification.
biomagnification is a process in which chemical substances become
more concentrated at each trophic level
(ii)
Outline a named example of biomagnification.
toxins/substances enter the body in water or food;
heavy metals are water soluble / synthetic organic compounds
are fat soluble;
heavy metals bind to enzymes / synthetic organic
compounds stored in fat;
no removal mechanism for heavy metals / synthetic
organic compounds cannot be metabolized;
example of chemical/mercury (e.g. DDT/organophosphorus/
TBT/PCB);
example of affect on top carnivore in food chain (e.g. thin
egg shells for birds of prey);
(b)
Outline the characteristics of a tropical rainforest biome.
The description should be limited to moisture, temperature and
characteristics of vegetation.
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lush vegetation;
great diversity of animals/plants;
e.g. forests of equatorial Africa;
evergreen;
high insolation;
high precipitation;
high temperature;
increased productivity;
high level of competition;
adaptations of leaves;
106. Discuss international measures that would promote the conservation of fish, including methods
used to measure conservation of fish stocks.
measures to promote conservation:
reduce total allowable catch below maximum sustainable yield/MSY;
limit areas where fishing can take place;
decrease total net size;
increase mesh size to let immature fish through / set minimum landing
sizes for fish;
reduce fishing effort;
reduce/stop subsidies for increasing size of fleet;
methods used to measure conservation:
monitor fish catches;
calculate the mass of fish that can be removed annually / maximum
sustainable yield;
required knowledge of birth rate, growth rate of fish and mortality rates;
can be estimated by looking at age structure of landed fish;
can be estimated by catch per fishing effort;
107. The food web below shows a community in central France 24 000 years ago.
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Which statement is a correct description of Ursus spelaeus?
A.
It is an omnivore which feeds on Lemmus lemmus.
B.
It is a producer preyed upon by Vaccinium oxycoccos.
C.
It is a top carnivore and a primary consumer.
D.
It is a decomposer and it competes with Rangifer tarandus.
(Total 1 mark)
108. Which diagram shows the flow of energy through a community with three trophic levels?
109. According to the precautionary principle, what should happen if there are fears that eating a
food might cause a health problem?
A.
People should be warned about the possible health problem.
B.
The company producing the food should be warned about the possible health problem.
C.
People who have fears about the food should test it to see if it causes a real health
problem.
D.
The company producing the food should test the food to prove that it does not cause a
health problem.
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110. If natality is slightly larger than mortality, and immigration is much larger than emigration, what
will happen to the size of a population?
A.
It will increase
B.
It will decrease
C.
It will fluctuate up and down
D.
It will remain constant
(Total 1 mark)
111. In the hierarchy of taxa, what is in a family?
A.
A group of classes
B.
A group of genera
C.
A group of orders
D.
A group of phyla
112. Methane produced by anaerobic bacteria contributes substantially to atmospheric methane
concentration. These bacteria are found in a variety of habitats. Some live inside the cytoplasm
of larger unicellular organisms and are known as endosymbionts. In marine sediments,
endosymbionts living in the cytoplasm of a group of unicellular organisms, known as ciliates,
can contribute up to 90% of methane production.
To see if endosymbionts in freshwater sediments had the same effect on methane production a
one-year study was carried out in Holland. The graph below shows the rate of methane
production by untreated sediment samples and sediment samples treated to kill the ciliates
containing endosymbionts. The standard deviations are indicated by bars. The total number of
ciliates is also indicated by circles.
(a)
State what the standard deviation indicates.
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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
(b)
State the maximum number of ciliates and the month in which the maximum occurs.
November had 113 (+2) ciliates ml-1 sediment
(c)
Compare the methane production in the untreated and treated samples.
production by treated and untreated samples is almost the same;
production by untreated samples is usually slightly higher than treated samples;
except Nov., January when the treated samples have a slightly higher methane production;
(d)
Deduce, with reasons, whether the endosymbionts in the ciliates are responsible for the
methane produced by the sediment samples.
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;
(e)
Explain how methane and other greenhouse gases cause global warming.
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;
Models predict global warming will cause sea temperatures to rise by approximately 2°C by
2100. An investigation was carried out to study the effect of slight increases in temperature on
the ability of Antarctic marine molluscs to carry out basic activities essential for survival.
The graph below shows the effect of temperature on the percentage of limpets (Nacella
concinna) able to right themselves after being turned over.
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(f)
Outline what the two parts of the scientific name Nacella concinna refer to.
first name / Nacella refers to the genus and the second name / concinna
refers to the species
(g)
State the relationship between temperature and the percentage righting in N. concinna.
negative correlation / inversely proportional / as temperature increases the
percentage righting in N. concinna decreases
(h)
Estimate the percentage change of N. concinna able to right themselves when the
temperature is raised from 0°C to 2.5°C.
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
(i)
At present, the maximum summer temperature in the normal Antarctic environment of
this organism is 1°C. Suggest what might be the effect on the survival of this organism if
the predicted rise in sea temperature due to global warming occurs.
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;
113.
(a) Outline the effect of light intensity on the rate of photosynthesis.
as light intensity increases rate of photosynthesis increases up to a
point when reaches maximum rate;
as light intensity increases beyond this maximum there is no further
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effect on rate;
(b)
Identify which phyla of plants fit each of the brief descriptions below.
(i)
Evergreen woody plant; leaves are shaped like needles; seed-producing with
reproductive structures in cones.
Phylum:
(ii)
Underground stem that bears roots and leaves called fronds; spores develop in
spore cases called sporangia located on the underside of fronds.
Phylum:
114.
coniferophyta
filicinophyta
(a) Explain the consequences of releasing raw sewage into a river.
raw sewage contains organic matter;
increase in N or P / eutrophication / algal bloom;
increase in bacteria / microbes (that feed on dead algae);
increased BOD / reduced dissolved oxygen;
oxygen sensitive organisms in river die / emigrate;
pollution sensitive organisms increase / diversity decreases;
increased levels of toxins / hormones / heavy metals;
(b)
Outline the habitat of methanogens.
anaerobic habitats;
marshes / guts of mammals / oxygen depleted soils;
115. The timing of breeding in tree swallows (Tachycineta bicolor) was studied in the United States
and Canada from 1959 to 1991. Figure A represents the mean egg laying date for each year. The
date is indicated as number of days after January 1st. Figure B shows the correlation between
mean May temperature (°C) and mean laying date over the same period.
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(a)
Identify the year with the earliest mean egg laying date.
1991
(b)
Outline the relationship between mean laying date and mean May temperature.
as mean temperature goes up, earlier mean laying date
(c)
Evaluate the evidence for global warming using figures A and B.
trend for egg laying being earlier over study period (in figure A);
higher temperatures lead to earlier egg laying;
egg laying correlated with warmer temperature;
data highly variable / evidence is indirect;
(d)
A change in mean laying date may increase competition with another species.
(i)
State the competitive exclusion principle.
only one species can occupy a niche within an ecosystem / niches
in an ecosystem will not overlap in the long term
(ii)
Apply the competitive exclusion principle to a change in mean laying date for the
tree swallow.
earlier egg laying date means that parents may compete for food / nesting
materials / nesting sites with other species or any example of how change
may cause niche to overlap;
tree swallow may expand range northward to hatch on the same day / tree;
tree swallow may cause a decline in population of species that now
overlaps niche / tree swallow may decline in population because of
overlapping niche or any ex. which shows the consequence of overlapping niche;
116.
(a) Define the term biomagnification.
(biomagnification) is a process in which chemical substances become
more concentrated at each trophic level
(b)
Outline one example of biomagnification.
example of chemical that was magnified eg DDT / mercury;
source / use of chemical substance eg weed killer / ground water contamination;
example of top heterotroph affected eg birds of prey / human;
consequence of biomagnification eg thin egg shells / birth deformities;
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117.
(a) Outline the temperature, moisture and vegetation characteristics of any one biome.
correctly named biome eg temperate deciduous forest;
level of precipitation eg moderate precipitation / 75–150 cm throughout
the year;
temperature range eg 15–18°C / warm summers and 3–7°C / cold winters /
significant annual temperature variation;
dominant plant eg dominant plants are broad leaf trees (that lose leaves
annually) / ecosystem characteristics eg significant diversity of understory
plants;
(b)
Discuss ecological arguments for the preservation of biodiversity.
species within an ecosystem are interdependent;
loss of one species affects a network of other species;
organism that expands to fill unoccupied niche might disrupt balance;
species impact abiotic factors;
example of impact on abiotic factor such as: increased erosion / decrease soil
fertility / microclimate changes etc;
human cultures / indigenous populations ability to live sustainably within
ecosystem might be affected;
118. Which group of organisms in the carbon cycle converts carbon into a form that is available to
primary consumers?
A.
Decomposers
B.
Detritus feeders
C.
Producers
D.
Secondary consumers
(Total 1 mark)
119. Which phylum does an animal belong to, if it has stinging tentacles and a mouth, but no anus?
A.
Annelida
B.
Cnidaria
C.
Porifera
D.
Platyhelminthes
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(Total 1 mark)
120. Up to two additional marks are available for the construction of your answers.
(2)
(a) Draw a labelled graph showing a typical sigmoid growth curve.
b)
Outline the consequences of an increased greenhouse effect on arctic ecosystems.
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;
(c)
Explain how natural selection leads to evolution.
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;
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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;
121.
a) State one example of a microbial photoautotroph and a microbial chemoautotroph.
Photoautotroph : Cyanobacteria
Chemoautotroph : Methanobacteria
(b)
Draw and label the nitrogen cycle.
122. The timing of breeding in tree swallows (Tachycineta bicolor) was studied in the United States
and Canada from 1959 to 1991. Figure A represents the mean egg laying date for each year. The
date is indicated as number of days after January 1st. Figure B shows the correlation between
mean May temperature (°C) and mean laying date over the same period.
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(a)
Identify the year with the earliest mean egg laying date.
1991
(b)
Outline the relationship between mean laying date and mean May temperature.
as mean temperature goes up, earlier mean laying date
(c)
Evaluate the evidence for global warming using figures A and B.
trend for egg laying being earlier over study period (in figure A);
higher temperatures lead to earlier egg laying;
egg laying correlated with warmer temperature;
data highly variable / evidence is indirect;
(d)
A change in mean laying date may increase competition with another species.
(i)
State the competitive exclusion principle.
only one species can occupy a niche within an ecosystem / niches
in an ecosystem will not overlap in the long term
(ii)
Apply the competitive exclusion principle to a change in mean laying date for the
tree swallow.
earlier egg laying date means that parents may compete for food / nesting
materials / nesting sites with other species or any example of how change
may cause niche to overlap;
tree swallow may expand range northward to hatch on the same day / tree;
tree swallow may cause a decline in population of species that now
overlaps niche / tree swallow may decline in population because of
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overlapping niche or any example which shows the consequence of
overlapping niche;
123.
(a) Define gross production.
(gross production =) net production + respiration;
(gross production is) the total amount of organic matter produced by
plants in an ecosystem;
(b)
Outline the characteristics of a desert biome
temperature is high during daytime and low during night time;
solar radiation during day is high / heat loss during night is high;
moisture is less than 500 mm rainfall per annum;
vegetation is spar
fauna is specialized;
124.
(a) Outline the factors that affect the distribution of animal species.
distribution is the range of places that an animal inhabits;
is closely linked to the levels of the abiotic & biotic factors of that environment;
main abiotic factors are water, temperature;
other factors include breeding sites, food supply and territory;
temperature, extremes of temperatures require special adaptations;
water, some animals are aquatic and some live in deserts;
breeding sites, special sites are needed to ascertain survival of offspring;
food supply, availability of special foods limits range of habitation;
territory, has an effect on the distribution of a species clumped rather than dispersed;
(b)
Discuss the environmental conditions that favour r-strategies.
r- strategists are usually small organisms that are found in an unstable
environment;
little advantage in adaptations that permit successful competition as the
environment is likely to change quickly;
are density independent;
environment should have ample supply of energy;
many offspring are produced so habitat should be able to support that;
early maturity so climate should favour this, eg short spring season in the
arctic regions;
short life expectancy so offspring also has a chance of survival;
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