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); 1

(ii) 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 max

(iii) 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 3 max

(b) 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

GURU CHARAN KUMAR/IB ESS 2012

(c) (i) D = ;

= 2.04; 3

(ii) 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; 1 max

Any other reasonable suggestion. [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) 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; 2

(b) (i) pyramid of numbers; 1

“pyramid” alone is insufficient; allow Eltonian pyramid.

Do not allow: biomass pyramid, food-chain, food-web.

(ii) parasites are usually much smaller than their host;

so many of them can feed on a single organism at a time; 2

more than one species of parasite may live on a single host;

parasites can breed more quickly than herbivores;

c) 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;

)2425()2425(

4950

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 (4)

predators

3) (a) (i) [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) 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

(iii) 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 4

for jellyfish and herring

4) (a) (i) 6 1

(ii) producers = first accumulator/algae, plants/level 1

top carnivores = ultimate accumulators/humans/level 6

Both required for [1] 1

(iii) 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

(b) (i) energy is used in respiratory processes at each trophic stage

and is lost as heat;

also lost as waste; 3

(ii) 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 [10]