This document contains a summary of a student's exam on environmental systems and societies from February 2013. It includes 4 questions on topics like biomass, net primary productivity, ecosystem structure and function, and human impacts. Question 1 defines biomass and describes methods to estimate total biomass. Question 2 asks about factors influencing biomass and NPP in different biomes. Question 3 defines ecological terms like ecosystem and discusses matter flows. Question 4 examines trophic efficiency and impacts of CFCs, acid deposition, and global warming on NPP.

1. GURU CHARAN KUMAR/IB ESS
HUMANITIES DEPARTMENT
ENVIRONMENTAL SYSTEM & SOCITIES
GRADE 11 SUMMATIVE- FEBURARY 2013
QUESTION 1
Question 2
a)
(i)
the mass of organic material in organisms or ecosystems,
usually per unit area;
(ii)
(b)
1
dry weight measurements are taken;
these figures are then extrapolated to estimate total biomass;
2
(i)
tropical rainforest;
1
(ii)
ideal growing conditions due to high temperatures (typically 28 °C);
and high rates of precipitation (typically over 2000 mm p.a.);
continuous growing season;

2. GURU CHARAN KUMAR/IB ESS
due to geographical location in equatorial area with sun
directly overhead;
for much of the year and energy of sun therefore concentrated
in this zone;
3
biomass is per unit area, productivity is production per unit time;
NPP is the quantity of biomass potentially available to
consumers in an ecosystem;
2
(i)
temperature deciduous woodland;
1
(ii)
deep humus means lots of organic matter and this leads to greater
fertility than acid humus (due to pine needles), therefore
coniferous is less fertile;
this soil has less leaching than the temperate coniferous
– i.e. fewer minerals washed out;
and parent material not as weathered as in tropical rainforest;
therefore likely to be contributing more minerals;
(iii)
(c)
3 max
[13]
QUESTION 3
(a)
a community of interdependent organisms and the physical environment
they inhabit/OWTTE;
1
(b)
e.g. water flow through a river ecosystem;
Accept any reasonable answer that identifies a flow and an ecosystem.
Award [0] if no named ecosystem.
1
(c)
biomass within trees and plants/nutrient within soil;
Do not accept for example “trees” or “soil”. The item stored must
be identified.
1
(d)
0.04;
1
(e)
e.g. tropical rainforest and tundra;
mean NPP tropical rainforest greater than tundra/mean biomass
tropical rainforest far greater than tundra;
NPP per kg biomass of tropical rainforest is far lower than tundra;
Candidates may give figures from the table but they need to make
comparative statements.
tropical rainforest hot and wet so greater opportunity to develop
large biomass/high rate of photosynthesis and high rate of
respiration so NPP/per kg biomass/per year is low;
tundra cold and dry so low rates of photosynthesis and respiration/
plants slow growing, slow accumulation of biomass, relatively large
growth in biomass per year;
Award up to [2 max] for comparison and up to [2 max] for
explanation. Award any other combination of two ecosystems.
(f)
name of primary producer: e.g. grassland;
method: [2 max]
collect all the vegetation (including roots, stems, leaves) within a
series of quadrats;
4 max

3. GURU CHARAN KUMAR/IB ESS
weigh vegetation;
dry the vegetation until no further weight loss is encountered/dry
weight represents biomass;
Award [2 max] if no named primary producer.
3 max
[11
QUESTION 4
(a) (i) The percentage of energy transferred from one trophic level to the next varies between
5% and 20% and is called the ecological efficiency.
(ii) Ecosystem E/mature tropical rain forest
Reason: any of climax community/higher habitat diversity/higher production base
(b) Any three of: solar radiation or light/ precipitation or water/ temperature/ pH/ soiltype/
climate. (But do not allow climate and either precipitation or temperature or both for the mark.)
(c) (i) 15 200
(ii) 14 400
24400
×100 = 59 %
correct answer [1]; correct working [1]
(iii) It is not a climax community [1]/ is a crop in a managed system [1];
has high inputs of fertiliser [1]/
and pesticides to eliminate food chains [1]/
energy subsidy [1]
(iv) high rate of respiration as temperature is high.[1]/
.. Production is lost in respiratory losses [1];
All NPP is used in HR [1]
or reasonable alternative explanation.
(d) (i) Increase in CFCs leads to loss of ozone layer [1];
more UV radiation damage to producers [1];
less photosynthesis so less GPP [1]
(ii) Acid deposition reduces tree growth [1]/
trees die back [1];
Al ions cause brittle stems [1];
increasing acidity of soil reduces NPP [1].
iii) Global warming [1];
as increased CO levels in atmosphere [1]; 2
as reduced sink for carbon [1]