1. GURU CHARAN KUMAR/IB ESS 2012
End of Semester Test November 2012
Grade: 11
Subject: Environmental Systems & Societies
Level: SL
Paper: 1
Duration: 1hour 30 minutes
Date: 21.11.2012
Maximum Mark: 80
Candidate Name: ______________________________
Subject Teacher: Guru Charan Kumar / Mesha Das
Instructions to Candidates
Section A: answer all of Section A in the spaces provided.
Additional Material
This question paper consists of 16 printed pages.
Page 1 of 16

2. GURU CHARAN KUMAR/IB ESS 2012
Page 2 of 16

3. GURU CHARAN KUMAR/IB ESS 2012
SECTION A
The graph below shows the interdependence of population size of two species of mites.
Eotetranychus sexmaculatus serves as the food supply for Typholodromus occidentalis.
50
E. sexmaculatus
2500
E. sexmaculatus
(prey)
T. occidentalis
(predator)
2000
40
1500
30
1000
20
500
T. occidentalis
1)
10
0
0
5
10
15
20
July
25
30
5
10
15
20
25
August
30
5
10
15
20
25
September
30
5
10
15
20
25
October
5
15
25
30 5 10 15 20 25 30 5 10 15 20 25 30 5 10 15 20 25 30
10
20
November
December
January
February
[Source: C B Huffaker, (1958), Hilgardia, Volume 27, pages 343–383.
Reprinted by permission of University of California Press.]
(a)
Predict when the next population maximum of T. occidentalis will occur. Show your
working.
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(2)
(b)
Determine the numbers of both organisms on September 30.
T. occidentalis: ............................................................................................................
E. sexmaculatus: ......................................................... . ..............................................
(1)
(c)
(i)
Identify the five day period for which the rate of increase of E. sexmaculatus is
at its maximum.
...........................................................................................................................
(1)
(ii)
Determine when the difference in numbers between both populations is at a
maximum.
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(1)
(d)
(i)
Calculate the time lag between the maximums of both species in the period
from October 5 through November 5.
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4. GURU CHARAN KUMAR/IB ESS 2012
...........................................................................................................................
........................................................................................................................... (1)
(ii)
Suggest a reason for this time lag.
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(1)
(e)
(i)
Describe the role that negative feedback might play in this species interaction.
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(2)
(ii)
Explain why the global human population is less prone to negative feedback
control than other organisms.
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(3)
(f)
Outline two examples of feedback in global warming.
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5. GURU CHARAN KUMAR/IB ESS 2012
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(2)
(Total 14 marks
2)
Figures 1 and 2 represent the food webs for two ecosystems.
Figure 1. Terrestrial Grassland
Sunlight
Grass
autotroph
Inorganic
material
Decay
and mineralization
Herbivore
heterotroph
Death
Carnivore
heterotroph
Figure 2. Marine Food Web
Human
Sperm whale
Baleen whale
Crabeater
seal
Small-toothed
whale
Leopard seal
Elephant
seal
Seabird
Fish
Squid
Carnivorous plankton
Krill
Herbivorous
Page 5 of plankton
16
Phytoplankton

6. GURU CHARAN KUMAR/IB ESS 2012
[Source: Tudge, C (1991) Global Ecology, The Natural History Museum, pp. 112–113]
(a)
(i)
State, giving three reasons, which of the food webs, Figure 1 or Figure 2, is
likely to be more stable.
...........................................................................................................................
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...........................................................................................................................
(3)
(ii)
Deduce what would happen to the ecosystem in Figure 1 if rabbits were
removed.
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...........................................................................................................................
(2)
(iii)
Predict two changes that may occur if foxes were removed from the food web in
Figure 1.
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(2)
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7. GURU CHARAN KUMAR/IB ESS 2012
Figure 3. Antarctic Marine Food Web
Baleen whales
Krill
Fish
Seals
Penguins
Squid
[Source: Trudge C (1991) Global Ecology, The Natural History Museum, pp. 113]
(b)
In Figure 3, the size of the circle represents the relative biomass of each animal
species within the food web.
Identify which of the diagrams in Figure 4 below best illustrates what would happen to
the food web balance in Figure 3,
(i)
if humans hunted for seals and fish.
...........................................................................................................................
(1)
(ii)
if humans harvested krill.
...........................................................................................................................
(1)
(Total 9 marks)
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8. GURU CHARAN KUMAR/IB ESS 2012
3)
(a)
Explain the 2 difference between an open system and a closed system.
...........................................................................................................................
...........................................................................................................................
(2)
(b)
The first and second laws of thermodynamics suggest that energy is neither made or
lost, merely transformed. Using a named ecosystem, outline how this occurs.
.....................................................................................................................................
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.....................................................................................................................................
.....................................................................................................................................
(2)
(c)
(i)
Explain how socio-political and economic pressures have caused or are causing
the degradation of a named area of biological significance.
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(3)
Page 8 of 16
(Total 7 marks)

9. GURU CHARAN KUMAR/IB ESS 2012
4)
a)
Examine the diagram below. It is not intended to represent any particular ecosystem
and the organisms are not shown to the same scale. Choose one of the organisms
shown in the diagram.
Write its name here .....................................................................................................
marsh plant
aquatic
invertebrate
phytoplankton
tree
bird
mammal
aquatic plants
amphibian
midge
larvae
fish
aquatic snail
aquatic plant
mussel
[Source: Adapted from Adds, J et al. The Organism and the Environment, 2nd edition (1997), page 81]
For the organism you have chosen, describe and evaluate a method for estimating its
abundance.
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10. GURU CHARAN KUMAR/IB ESS 2012
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(5)
(b)
Explain why it might be important to know the abundance of the species of organisms
in an ecosystem in assessing that ecosystem’s diversity.
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(2)
(c)
State how you would attempt to identify an organism with which you were unfamiliar.
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(2)
(d)
(i)
Name and briefly describe an ecosystem of which you have made a special
study.
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
Describe one human activity that might influence your chosen ecosystem.
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(1)
(iii)
State one abiotic factor that might be changed by this human activity.
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11. GURU CHARAN KUMAR/IB ESS 2012
(1)
(iv)
Explain how this human activity might change the abiotic factor.
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(2)
(v)
Outline how you would measure changes in this abiotic factor.
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(2)
(e)
(i)
Explain, with an example, what is meant by the term Trophic levels.
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(2)
(ii)
Explain how you would measure the changes in the species diversity of an
ecosystem.
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(2)
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12. GURU CHARAN KUMAR/IB ESS 2012
(Total 20 marks
5)
The following is a schematic diagram of an “ecotron”. This is a walk-in chamber with
computer controlled climatic conditions for studying small communities representative of
natural ecosystems.
lighting
airtight transparent
ceiling
irrigation system
air outlet
plant, animal
and decomposer
communities
sensors
air pump
Scale: 1m
[Source: modified from NERC www.cpb.bio.ic.ac.uk/ecotron/ecotron.html]
(a)
State whether this is an open, closed or isolated system. Give one reason for your
answer.
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......................................................................................................................................
(1)
(b)
Identify and explain two ways in which the inputs to the system would differ from the
outputs while communities are growing within the ecotron.
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(4)
(c)
If a fall in temperature of the system is detected by the sensors, mechanisms will be
automatically initiated to increase the temperature. State which kind of feedback this
demonstrates.
......................................................................................................................................
(1)
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13. GURU CHARAN KUMAR/IB ESS 2012
(d)
(i)
Outline how the second law of thermodynamics can explain the pyramid shape
associated with most food chains including that found in the ecotron.
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(2)
(ii)
In this context, explain why food chains studied in the ecotron are generally
limited to no more than three trophic levels.
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(2)
(Total 10 marks)
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14. GURU CHARAN KUMAR/IB ESS 2012
6)
a)
Define the term biodiversity.
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(2)
(b)
Simpson’s diversity index is D =
(i)
N ( N 1)
n( n 1)
State what the symbol n represents in the above equation.
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
Suggest what a high D value indicates about an ecosystem.
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(1)
(iii)
Predict the effect on the value of D if the number of organisms of one species
increased but the total number of organisms of all other species in an ecosystem
remained constant.
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...........................................................................................................................
(1)
(iv)
Suggest one reason for a low D value in an ecosystem.
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(1)
(c)
(i)
Outline a method for estimating plant biomass within a named ecosystem.
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15. GURU CHARAN KUMAR/IB ESS 2012
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(3)
(ii)
Outline a method for estimating the abundance of small mammals in a tundra
environment.
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(2)
(Total 11 marks)
7) The figure below shows the range of tolerance to temperature for a fish population.
Lower limit
of tolerance
No
organisms
Zone of
intolerance
Upper limit
of tolerance
Few
organisms
Zone of
physiological
stress
Abundance
of organisms
Optimum range
Temperature
Low
Few
organisms
No
organisms
Zone of
physiological
stress
Zone of
intolerance
High
[MILLER, Living in the Environment, 7E. © 1992 Brooks/Cole, a part of Cengage Learning, Inc.
Reproduced by permission. www.cengage.com/permissions]
(a)
(i)
Outline what the figure above shows about fish density and temperature.
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Page 15 of 16

16. GURU CHARAN KUMAR/IB ESS 2012
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(2)
(ii)
Explain what is meant by a limiting factor in the context of the fish population
in this lake.
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(1)
(iii)
State, giving a reason, whether temperature is a density-dependent or densityindependent factor in the regulation of fish populations.
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...........................................................................................................................
(1)
(b)
Temperature is an abiotic feature of an ecosystem. List four other abiotic factors of an
ecosystem.
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(2)
(c)
With reference to one abiotic factor you have named in (b), outline and evaluate a
method for measuring this factor.
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(3)
(Total 9 marks)
Page 16 of 16