1. GURU CHARAN KUMAR/IB ESS 2012
HUMANITIES DEPARTMENT
ESS GRADE 11 SUMMATIVE-ANSWER SCHEME-SEPTEMBER 2012
1) (a) (i)
name and brief description (e.g. intertidal rock pool
at Tagus river, Portugal);
(ii)
(iii)
Candidates must state two abiotic factors appropriate
to ecosystem to receive [1].
e.g.
salinity;
pH;
temperature;
dissolved oxygen;
wave action;
turbidity;
flow velocity;
light intensity;
wind speed;
particle size;
slope;
soil moisture;
drainage;
mineral content;
1
1 max
Take quantitative samples – known area or volume
Measure the whole habitat size
Dry samples to remove water weight
Take Dry mass for sample then extrapolate to entire trophic level
Evaluation:It is an estimate based on assumption that
all individuals at that trophic level are the same
The sample accurately represents the whole habitat
(b)
3 max
appropriate example (name of organism);
Award [1] for appropriate method.
e.g. non-motile animal or plant by quadrat;
Method must be appropriate for the species named.
Award [1] for description.
repeat sampling procedure (time);
ensure sampling is consistent and replicated;
calibration of instrument;
location of sampling;
Award [1] for evaluation of method. Take account of e.g.:
birth;
death;
immigration;
emigration;
4 max

2. GURU CHARAN KUMAR/IB ESS 2012
(c)
(i)
(ii)
50 49
;
(25 24) (25 24)
= 2.04;
D=
there is a difference between the (relative) abundance of
organisms;
one area has been disturbed by human activities;
two areas are at different seral stages;
Any other reasonable suggestion.
3
1 max
[12]
iii) Diagram showing at least three organisms (two links) [1]
e.g. Grevillea leaves → caterpillar → kookaburra;
Spinifex seeds → ants → lizard → snake → eagle;
grass → cow → human;
The names of organisms are not actually required in the question so a
generalized diagram is acceptable:
green plant/producer → herbivore/primary consumer → carnivore/secondary
consumer;
Do not award credit for a food web diagram; arrows must be in correct direction.
explanation [1]
a series of organisms at different trophic levels (that occur in the same
environment/ habitat)
2 max
(Total 16 marks)
2) (a)
(b)
a parasite lives in or on another (host) organism/species and gains all
or much of its food from that organism (usually without killing it)
OWTTE;
a predator is an animal that hunts another animal and kills it for
food OWTTE;
pyramid of numbers;
“pyramid” alone is insufficient; allow Eltonian pyramid.
Do not allow: biomass pyramid, food-chain, food-web.
(ii)
c)
(i)
parasites are usually much smaller than their host;
so many of them can feed on a single organism at a time;
more than one species of parasite may live on a single host;
parasites can breed more quickly than herbivores;
energy available higher up a food chain is limited by energy fixed
by producers;
losses due to respiration reduce available energy/much energy
(about 90%) is converted to heat at each level of the food chain;
because all organisms must transform some energy to heat to
carry out their metabolic functions;
as implied by the Second Law of thermodynamics;
2
1
2

3. GURU CHARAN KUMAR/IB ESS 2012
predators are always near the top of food chain/at third trophic
level or above;
so much of the available energy/production from producers is
converted to heat and lost from the system before it reaches the
predators
3) (a) (i)
(4)
[1] for every two correctly placed in the table.
3 max
Producer
Primary
Consumer
Secondary
Consumer
Tertiary
Consumer
Decomposer
phytoplankton
zooplankton
jellyfish
puffins
dolphins
crustaceans
(ii)
(iii)
4) (a) (i)
energy is lost as heat/through respiration at each stage in
the food chain;
so after 4 or 5 trophic stages there is not enough energy to
support another stage;
3
sand eels are the only source of food for mackerel, puffin and
gannet;
so numbers of these species may decline/they may have to
switch food source;
seals will have to rely more on herring, possibly reducing
their numbers/may have to switch food source;
amount of zooplankton may increase improving food supply
for jellyfish and herring
4
6
1
(ii)
producers = first accumulator/algae, plants/level 1
top carnivores = ultimate accumulators/humans/level 6
Both required for [1]
1
pesticide becomes increasingly concentrated as you go up
the food chain;
because each successive trophic level supports fewer
organisms and so the pesticide becomes concentrated in
the tissues;
a progressively longer life span – intake of many individuals
of a lower level;
2
energy is used in respiratory processes at each trophic stage
and is lost as heat;
also lost as waste;
3
pyramid of biomass represents biomass at a given time;
whereas pyramid of productivity represents rate at which
stocks are being generated;
pyramid of biomass is measured in units of mass/
energy/J m–2/g m–2 ;
pyramid of productivity is measured in units of flow/
J m–2 yr–1/g m–2 yr–1;
3
(iii)
(b)
(i)
(ii)
[10]