IBESS - Topic 2 Review: Chapters 3, 14, 16
Topic 2: The Ecosystem (31 hours)
38 Review Points
2.1 Structure
Obj.
2.1.1
Assessment Statement
Distinguish between biotic and abiotic (physical) components
of an ecosystem.
2.1.2
2.1.3
Define the term trophic level.
Identify and explain trophic levels in food chains and food webs
selected from the local environment.
2.1.4
Explain the principles of pyramids of numbers, pyramids of
biomass, and pyramids of productivity, and construct such
pyramids from given data.
Notes
Relevant terms (for example, producers, consumers,
decomposers, herbivores, carnivores, top carnivores) should be
applied to local, named examples and other food chains and
food webs.
Pyramids are graphical models of the quantitative differences
that exist between the trophic levels of a single ecosystem. A
pyramid of biomass represents the standing stock of each
trophic level measured in units such as grams of biomass per
square metre (g m-2). Biomass may also be measured in units of
energy, such as J m-2.
In accordance with the second law of thermodynamics, there is
a tendency for numbers and quantities of biomass and energy
to decrease along food chains; therefore the pyramids become
narrower as one ascends.
Pyramids of numbers can sometimes display different patterns,
for example, when individuals at lower trophic levels are
relatively large. Similarly, pyramids of biomass can show
greater quantities at higher trophic levels because they
represent the biomass present at a given time (there may be
marked seasonal variations). Both pyramids of numbers and
pyramids of biomass represent storages.
Pyramids of productivity refer to the flow of energy through a
trophic level and invariably show a decrease along the food
chain. For example, the turnover of two retail outlets cannot be
compared by simply comparing the goods displayed on the
shelves; the rates at which the shelves are being stocked and
the goods sold also need to be known. Similarly, a business may
have substantial assets but cash flow may be very limited. In
the same way, pyramids of biomass simply represent the
momentary stock, whereas pyramids of productivity show the
rate at which that stock is being generated. Biomass, measured
in units of mass or energy (for example, g m–2 or J m–2), should
be distinguished from productivity measured in units of flow
(for example, g m–2yr–1 or J m–2yr–1).
2.1.5
Discuss how the pyramid structure affects the functioning of an
ecosystem.
2.1.6
Define the terms species, population, habitat, niche,
communityand ecosystem with reference to local examples.
A pyramid of energy may be represented either as the standing
stock (biomass) measured in units of energy (J m–2) or as
productivity measured in units of flow of energy (J m–2yr–1),
depending on the text consulted. As this is confusing, this
syllabus avoids the term pyramid of energy.
This should include concentration of non‑biodegradable toxins
in food chains, limited length of food chains, and vulnerability
of top carnivores. Definitions of the terms biomagnification,
bioaccumulation and bioconcentration are not required.
2.2 Measuring Abiotic Components of the System
Obj.
2.2.1
Assessment Statement
List the significant abiotic (physical) factors of an ecosystem.
Notes
2.2.2
Describe and evaluate methods for measuring at least three
abiotic (physical) factors within an ecosystem.
Students should know methods for measuring any three
significant abiotic factors and how these may vary in a given
ecosystem with depth, time or distance. For example:
• marine—salinity, pH, temperature, dissolved oxygen, wave
action
• freshwater—turbidity, flow velocity, pH, temperature,
dissolved oxygen
• terrestrial—temperature, light intensity, wind speed, particle
size, slope, soil moisture, drainage, mineral content.
This activity may be carried out effectively in conjunction with
an examination of related biotic components.
2.3 Measuring Biotic Components of the System
Obj.
2.3.1
Assessment Statement
Construct simple keys and use published keys for the
identification of organisms
Notes
Students could practise with keys supplied and then construct
their own keys for up to eight species.
2.3.2
Describe and evaluate methods for estimating abundance of
organisms.
2.3.3
Describe and evaluate methods for estimating the biomass of
trophic levels in a community.
Define the term diversity.
Methods should include capture–mark–release– recapture
(Lincoln index) and quadrats for measuring population density,
percentage frequency and percentage cover.
Dry weight measurements of quantitative samples could be
extrapolated to estimate total biomass.
Diversity is often considered as a function of two components:
the number of different species and the relative numbers of
individuals of each species.
𝑁(𝑁 − 1)
𝐷=
∑ 𝑛(𝑛 − 1)
2.3.4
2.3.5
Apply Simpson’s diversity index
and outline its significance.
Students are not required to memorize this formula but must
know the meaning of the symbols:
D = diversity index
N = total number of organisms of all species found
n = number of individuals of a particular species
D is a measure of species richness. A high value of D suggests a
stable and ancient site, and a low value of D could suggest
pollution, recent colonization or agricultural management. The
index is normally used in studies of vegetation but can also be
applied to comparisons of animal (or even all species) diversity.
2.4 Biomes
Obj.
2.4.1
Assessment Statement
Define the term biome
2.4.2
Explain the distribution, structure and relative productivity of
tropical rainforests, deserts, tundra and any other biome.
Notes
Biomes usually cross national boundaries (biomes do not stop
at a border; for example, the Sahara, tundra, tropical
rainforests).
Refer to prevailing climate and limiting factors. For example,
tropical rainforests are found close to the equator where there
is high insolation and rainfall and where light and temperature
are not limiting. The other biome may be, for example,
temperate grassland or a local example. Limit climate to
temperature, precipitation and insolation.
2.5 Function
Obj.
2.5.1
Assessment Statement
Explain the role of producers, consumers and decomposers in
the ecosystem.
Notes
2.5.2
Describe photosynthesis and respiration in terms of inputs,
outputs and energy transformations.
Biochemical details are not required. Details of chloroplasts,
light-dependent and light independent reactions,
mitochondria, carrier systems, ATP and specific intermediate
biochemicals are not expected.
Photosynthesis should be understood as requiring carbon
dioxide, water, chlorophyll and certain visible wavelengths of
light to produce organic matter and oxygen. The
transformation of light energy into the chemical energy of
organic matter should be appreciated.
2.5.3
Describe and explain the transfer and transformation of energy
as it flows through an ecosystem.
Respiration should be recognized as requiring organic matter
and oxygen to produce carbon dioxide and water. Without
oxygen, carbon dioxide and other waste products are formed.
Energy is released in a form available for use by living
organisms, but is ultimately lost as heat.
Explain pathways of incoming solar radiation incident on the
ecosystem including:
• loss of radiation through reflection and absorption
• conversion of light to chemical energy
• loss of chemical energy from one trophic level to another
• efficiencies of transfer
• overall conversion of light to heat energy by an ecosystem
• re-radiation of heat energy to the atmosphere.
Construct and analyse simple energy-flow diagrams illustrating
the movement of energy through ecosystems, including the
productivity of the various trophic levels.
The distinction between storages of energy illustrated by boxes
in energy-flow diagrams (representing the various trophic
levels), and the flows of energy or productivity often shown as
arrows (sometimes of varying widths) needs to be emphasized.
The former are measured as the amount of energy or biomass
per unit area and the latter are given as rates, for example, J m2
day-1.
2.5.4
Describe and explain the transfer and transformation of
materials as they cycle within an ecosystem.
2.5.5
Define the terms gross productivity, net productivity, primary
productivity and secondary productivity.
Define the terms and calculate the values of both gross primary
productivity (GPP) and net primary productivity (NPP) from
given data.
Define the terms and calculate the values of both gross
secondary productivity (GSP) and net secondary productivity
(NSP) from given data.
2.5.6
2.5.7
Processes involving the transfer and transformation of carbon,
nitrogen and water as they cycle within an ecosystem should
be described, and the conversion of organic and inorganic
storage noted where appropriate.
Construct and analyze flow diagrams of these cycles.
Productivity is production per unit time.
Use the equation
NPP = GPP – R
where R = respiratory loss
Use the equations
NSP = GSP – R
GSP = food eaten – fecal loss
where R = respiratory loss
The term “assimilation” is sometimes used instead of
“secondary productivity”.
2.6 Changes
Obj.
2.6.1
Assessment Statement
Explain the concepts of limiting factors and carrying capacity in
the context of population growth
Notes
2.6.2
Describe and explain S and J population curves.
Explain changes in both numbers and rates of growth in
standard S and J population growth curves.
Population curves should be sketched, described, interpreted
and constructed from given data.
2.6.3
2.6.4
2.6.5
Describe the role of density‑dependent and density‑
independent factors, and internal and external factors, in the
regulation of populations.
According to theory, density-dependent factors operate as
negative feedback mechanisms leading to stability or
regulation of the population.
Describe the principles associated with survivorship curves
including, K‑ and r‑strategists.
Both types of factors may operate on a population. Many
species, particularly r‑strategists, are probably regulated by
density independent factors, of which weather is the most
important. Internal factors might include density-dependent
fertility or size of breeding territory, and external factors might
include predation or disease.
K‑ and r‑strategists represent idealized categories and many
organisms occupy a place on the continuum.
Describe the concept and processes of succession in a named
habitat.
Students should be familiar with interpreting features of
survivorship curves including logarithmic scales.
Students should study named examples of organisms from a
pioneer community, seral stages and climax community.
The concept of succession, occurring over time, should be
carefully distinguished from the concept of zonation, which
refers to a spatial pattern.
2.6.6
Explain the changes in energy flow, gross and net productivity,
diversity and mineral cycling in different stages of succession.
2.6.7
Describe factors affecting the nature of climax communities.
In early stages, gross productivity is low due to the initial
conditions and low density of producers. The proportion of
energy lost through community respiration is relatively low
too, so net productivity is high, that is, the system is growing
and biomass is accumulating.
In later stages, with an increased consumer community, gross
productivity may be high in a climax community. However, this
is balanced by respiration, so net productivity approaches zero
and the production:respiration (P:R) ratio approaches one.
Climatic and edaphic factors determine the nature of a climax
community. Human factors frequently affect this process
through, for example, fire, agriculture, grazing and/or habitat
destruction.
2.7 Measuring Changes in the System
Obj.
2.7.1
Assessment Statement
Describe and evaluate methods for measuring changes in
abiotic and biotic components of an ecosystem along an
environmental gradient.
Describe and evaluate methods for measuring changes in
abiotic and biotic components of an ecosystem due to a
specific human activity.
2.7.2
2.7.3
Describe and evaluate the use of environmental impact
assessments (EIAs).
Notes
Methods and changes should be selected appropriately for the
human activity chosen. Suitable human impacts for study might
include toxins from mining activity, landfills, eutrophication,
effluent, oil spills and overexploitation. This could include
repeated measurements on the ground, satellite images and
maps.
Students should have the opportunity to see an actual EIA
study. They should realize that an EIA involves production of a
baseline study before any environmental development,
assessment of possible impacts, and monitoring of change
during and after the development.
Multiple Choice ( ¼ point each)
1. Which of the following is a characteristic of K-selected organisms?
a. They are typical of pioneer communities.
b. Usually a very high percentage of young die during the early part of their life cycle.
c. Sexual maturity is reached early in the lifespan.
d. They usually have a high degree of parental care of young.
2.
In a survey of an antelope population, 80 antelope were marked and released. Two weeks later a second sample was
captured, of which 16 antelope were found unmarked and 4 were marked. What is the estimated population size?
a. 100
b. 200
c. 400
d. 1600
3.
Which of the following represents an example of photosynthesis?
a. water + carbon dioxide + energy → glucose + oxygen
b. glucose + oxygen → water + carbon dioxide + energy
c. water + carbon dioxide → glucose + oxygen + water + energy
d. nitrogen + carbon dioxide + energy → methane + oxygen
4.
Net Primary Production is the amount of energy
a. produced from ‘alternative’ sources in developing countries.
b. fixed in an ecosystem by photosynthesis.
c. fixed in an ecosystem by photosynthesis, minus the losses due to respiration by producer organisms.
d. fixed by the herbivores in an ecosystem.
5.
Which of the following correctly describes the components of a population, community, ecosystem and habitat?
A.
B.
C.
D.
6.
Population
Biotic only
Biotic only
Biotic and abiotic
Biotic only
Community
Biotic only
Biotic and abiotic
Biotic and abiotic
Biotic only
Ecosystem
Biotic and abiotic
Biotic and abiotic
Biotic only
Biotic and abiotic
Habitat
Biotic and abiotic
Biotic and abiotic
Abiotic only
Abiotic only
An animal population is given 50 kg of feed per day, of which 40 kg is consumed. 20 kg of feed per day is used in
respiration and 15 kg of faeces per day is released. Which of the following are the correct values for gross and net
productivity?
A.
B.
C.
D.
Gross Productivity
(kg day-1)
40
25
50
40
Net Productivity
(kg day-1)
25
5
35
5
7.
The main deserts of the world are found at
a. latitudes between the tundra and temperate forests.
b. lower latitudes than temperate and tropical forests.
c. latitudes between the temperate and tropical forests.
d. higher latitudes than the tundra.
8.
The diagram below shows a complete food web. Each letter represents a species.
P
R
H
L
S
F
E
G
T
N
O
Which are secondary consumers?
a. G, S, R, P and F
b. H and P
9.
c. N, L, E and T
d. O
As succession approaches a climax, which changes are likely to occur in an ecosystem?
Gross productivity of
Net productivity of
Inorganic mineral
whole ecosystem
whole ecosystem
storages
A.
Increase
Increase
Increase
B.
Decrease
Increase
Decrease
C.
Increase
Decrease
Decrease
D.
Increase
Decrease
Increase
10. The main factors that determine the type of biome found are
I. temperature.
II. precipitation.
III. soil type.
IV. wind direction.
a. I and II only
b. I and III only
c.I, II and IV only
d.I, II, III and IV
k
j
carnivores
h
g
i
herbivores
e
d
f
producers
b
D E C O M P O S E R S
R E
S P I R A T I O N
11. The diagram below shows the flow of energy through a food web.
c
sunlight not
used in
photosynthesis
sun
a
Gross Primary Productivity (GPP) is
a. b – c
b. b – a.
c. b.
d. b – c – d.
12. Refer to the diagram in question 10. Net Primary Productivity (NPP) is
a. b – c – d.
b. d + e + f.
c. e.
d.e – d.
13. Below is the diagram of the nitrogen cycle.
Organic
residues
Animals
Ammonium
ions
Plants
IV
I
Nitrite ions
Atmospheric
nitrogen
III
II
Nitrate ions
Denitrification is
a. I.
b. II
c. III
d. IV.
14. An increase in parasitism, causing reduced survival in a host population as that population increases in size, is an
example of
a. an internal regulating factor.
c.a density independent factor.
b. positive feedback.
d. a density dependent factor.
15. If toxic materials were to be released into a coral reef ecosystem, in which part of the ecosystem would you expect
them to accumulate to the greatest extent?
a. In the algae living amongst the corals
c. In the open water
b. In the tissues of small fish
d. In the tissues of large carnivorous fish such as sharks
16. Which of the following can generally be deduced from the shape of the survivorship curves for a given species?
a. Number of births per year
b. Maximum rate of population growth
c. Carrying capacity for a given population
d. Relative amount of parental care and investment per individual offspring
Paper 1 Response Practice
1. A study has been made of the number of flowering plant species that occur on six islands off the coast of the same
country. The graph below shows the relationship between the area (in km2) of each of the islands and the number of
flowering plant species found on them.
140
120
100
80
Number of flowering
plant species
60
40
20
0
0
1
2
3
4
5
6
7
8
9
10
Area of island / km 2
(a)
Describe the relationship between island area and plant diversity shown by the graph.
(2 points)
positive relationship/species diversity increases as island areaincreases;
as island size increases, rate of increase in number of plant
species decreases/steepness of curve decreases;
2 max
(b)
Suggest one possible reason for the relationship described in (a).
number of habitats increases with island area/larger islands more
complex ecosystems;
larger islands have longer shores, therefore more likely to receive
drifting seeds, fruits, etc.;
larger islands more likely to be nesting sites for seabirds and
therefore to have seeds,
fruits brought from mainland;
larger islands more likely to be conserved;
larger islands can support larger populations of a given organism
and so extinction is less likely;
Any reasonable alternative explanation.
(c)
(1 point)
1 max
Predict the effects of the introduction of goats or some other species of large herbivore on a small island
ecosystem.
(2 points)
reduction in plant biomass;
reduction in number of plant species;
increase in very low “ground-living” plant species;
competition with and decline of any other herbivorous species;
trampling and soil erosion;
accelerated turnover of nutrients (especially N, P) though herbivore excretion;
Any reasonable alternative explanation.
2 max
2.
The table below gives the mean dry weight biomass for the primary producers in certain ecosystems.
Ecosystem
Tropical rainforest
Deciduous forest
Boreal (coniferous) forest
Grassland
Tundra
Desert
Freshwater lake
(a)
(i)
Define the term dry weight biomass.
Biomass/kg m–2
45.0
35.0
30.0
6.0
0.6
0.2
0.1
(1 point)
the weight/mass of (organic) material, after the removal of water;
(ii)
For one of the ecosystems listed above, describe and evaluate a method for obtaining such dry weight
biomass data.
(4 points)
Selected ecosystem ...........................................................................................
Method
Methodology will vary slightly with ecosystem chosen.
Award [1] for each of the following up to [4 max]. Award [3 max]
if no evaluation of (E) points given.
mark out measured area;
select quadrats using an appropriate method;
harvest all plant material within sample area;
air dry/oven dry;
Do not accept ‘burn’
weigh;
ideally take several samples and obtain mean;
problems with very large trees/difficult to harvest/destruction
of ecosystem (E);
problems with estimation of subterranean biomass (especially
in forest ecosystems) (E);
Any other reasonable point
Points of methodology inappropriate to selected ecosystem should
not be credited.
Reject any discussion of animals/secondary productivity
(iii)
4 max
Name one abiotic factor important in the ecosystem you have selected, and describe how you would study
its variation over time.
(3 points)
Methodology will depend on abiotic factor chosen and must
be appropriate to the selected ecosystem.
name of factor (e.g. temperature, rainfall);
Do not accept a biotic factor
brief methodology (e.g. use thermometer/thermograph/raingauge);
repeat observation under similar conditions regularly overperiod/day/year;
The table below gives the number of individuals of four species of trees in two small patches of Australian forest.
Tree species
Allocasurinahuegelina
Banksiagrandis
Eucalyptus calophylla
Acacia saligna
(b)
(i)
Area A
4
5
7
4
Area B
1
8
9
2
Using the formula for Simpson’s diversity index
N(N  1)
n(n  1)
D=
calculate which of area A or area B has the higher diversity index. Show your working.
(3 points)
20 19
380
= 4.4

12  20  42  12 86
20 19
380
area B:
= 2.9

0  56  72  2 130
Accept more but not less significant figures than above.
therefore, area A is the most diverse area;
[1] for correct method, [1] for correct answers. Award [1] foridentifying area A.
Allow ECF for final point, but no mark if no working shownat all
area A:
(ii)
Name one environmental factor that might explain this difference.
(1 point)
Award [1] for any reasonable factor e.g.
succession;
soil texture;
moisture;
pH of soil;
logging/burning;
light intensity;
1 max
Reject a statement about number of species and abundance of species.
The sketch below shows four types of termite found in Australia. (Termites are burrowing, colonial insects.)
[Source: ‘Some Termites from Western Australia’, (1989).Reprinted with the permission of the Western Australian
Gould League Inc.]
(c)
(i)
List three characteristics displayed by the organisms illustrated above that might be used to construct a
keyto assist in identifying termites from the same part of Australia.
(2 points)
Award [1] for two of the following and [2] for three
presence of wings;
presence of pincers;
steeply curved antennae/feelers;
abdomen more than twice the size of head and thorax/
relative size of head, thorax, abdomen;
horn-like structure on head;
absolute size;
Any other reasonable suggestion
Reject number of legs. All the specimens shown have six,
as do almost all (adult) insects.
(ii)
2 max
Name two methods, other than the use of a key, that you might use to identify an insect you had not seen
before.
(2 points)
Award [1] for each of the following:
use field guide/illustrated textbook;
compare with museum specimen;
internet resources, OWTTE;
consult expert on the group;
distribution;
DNA testing;
behaviour (including sound);
habitat;
time of day or year;
Any other reasonable points
(iii)
Bearing in mind that termites live in colonies of many thousands of individuals, and that these colonies
sometimes form large mounds, suggest how you might estimate the number of termites on five hectares of
land. Evaluate your methods.
(4 points)
Award [3 max] for method and [1 max] for evaluation.
methods:
simple numerical count of termite mounds;
sample area might be taken and result multiplied to give total
figure;
mean of several samples might be taken;
use aerial photos to count mounds;
(Reject use of satellite images: scale probably too small).
use catch – release – recapture/Lincoln index method to
estimate number of termites in a colony;
multiply estimate of numbers in colony by number of colonies;
evaluation:
problems of dealing with very large numbers;
difficulty of access to interior of termite mound;
problems of variation in numbers with season;
difficulty of estimated numbers outside mound foraging;
Lincoln index method may not be appropriate for termite
community if organisms do not move around randomly between
marking and recapture;
problems of recruitment to population and deaths between
marking and recapture;
max
Any other reasonable suggestions for method or evaluation
4
When marking be tolerant: reward adequate understanding
of methods or concepts. However, award [3 max] if mounds
are not mentioned at all or if an account focuses solely on
mounds to the exclusion of actual insects.
3.
The figure below gives information on the character and role of mangroves and their interdependence with coral
reefs.
Character and role of mangroves
LAND
Muds are soft, so arched
roots strengthen trees
against strong winds
and waves.
Tides move in and out daily.
Mangrove forests protect
coast against storms and
erosion.
Exposed roots take in oxygen and
give out carbon dioxide.
Young plants are established. High water
Low water
Raised roots collect mud
washed in by tides. Slowly
the coast is built out.
Mangrove–coral reef interdependence
Mangrove roots and sea Adult shrimps, lobsters
grass in shallow water, fish move out to main
reef.
act as “nurseries” for
young sea creatures.
Leaf fragments feed Mangrove roots and
shrimps, crabs,
sea grass filter out sediment
and chemicals from water.
young fish.
Sunlight penetrates
clear water.
Reef is cleansed
by tidal movements.
Main coral reef
Mangrove forest
Sea grass
[Source: adapted from Prosser, Natural Systems and Human Responses, Nelson 1992, page 227]
(a)
Using the information in the figure only, identify examples of the following components of the mangrovecoral reef ecosystem.
(1 point)
(i)
A producer .......................................................................................................
mangrove tree / coral / sea grass;
(ii)
A consumer ......................................................................................................
crab / fish / shrimp / lobster / coral;
(b)
The figure illustrates the gradual change in a living community which occurs over time. State the name of
this process.
(1 point)
(c)
Construct a simple flow diagram to show how energy passes through the mangrove-coral reef ecosystem.
(3 points)
succession
sunlight … converted by mangrove and coral provides food for primary
consumer e.g. shrimp … provides food for secondary consumers large
fish etc … eventually die and broken down by decomposers;
3 max
[1] for diagram, [2] for information.
(d)
(i)
Outline the possible impact of the removal of mangroves on
the rest of the ecosystem.
(2 points)
nurseries for young sea creatures lost so fewer survive
into adulthood;
coral becomes swamped with sediment as mangrove roots
no longer filter it out;
more sediment in water means water is less clear / more
turbid and coral productivity declines;
(ii)
people living in the area.
loss of income from fishing and tourism as coral
dies and fewer fish in this area;
more coastal erosion as protection from storms is lost;
(2 points)
(Question 4 Practice Only – No Points Awarded)
4. (a)
(i)
Name and briefly describe an ecosystem you have studied. State two abiotic factors significant in the
ecosystem.
(1 point)
name and brief description (e.g. intertidal rock pool at Tagus river, Portugal)
salinity;
pH;
temperature;
dissolved oxygen;
wave action;
turbidity;
flow velocity;
light intensity;
wind speed;
particle size;
slope;
soil moisture;
drainage;
mineral content;
(ii)
Outline and evaluate a method to measure one of the selected abiotic factors.
(3 points)
freshwater ecosystem, abiotic factor – temperature
use thermometer;
take account of: temperature may change with depth of the lake;
temperature may change at different hours of the day/seasons;
so need to take several observations to calculate mean;
aquatic ecosystem, abiotic factor – pH
use pH meter/pH paper;
take account of: pH is a logarithmic scale (increase of
1 point on the scale represents 10 times);
pH may change with depth of water column;
so need to take several observations to calculate mean;
terrestrial ecosystem, abiotic factor – soil texture
use of sieves;
use of triangular graph with proportions of sand, silt and clay;
take account of: field sample may be wet, so must be
dried before testing;
sample must be well shaken to separate particles;
soil may vary within profile/locally;
so need to take several samples;
presence of living organisms;
presence of organic matter;
(b)
3 max
Name an organism found in the ecosystem specified above. Describe and evaluate a method for estimating
its abundance.
(4 points)
appropriate example (name of organism);
Award [1] for appropriate method.
e.g. non-motile animal or plant by quadrat;
transect sampling;
by capture-mark-recapture if motile animal;
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
Two areas of forest each contain 50 trees. The species composition of the two areas is as follows.
Area A
Area B
Eucalyptus
42
25
Casurina
8
25
Simpson’s diversity index can be calculated by applying the formula below,
(c)
N ( N  1)
n(n  1)
where:
(i)
D=
N = total number of organisms of all species,
n = number of organisms of a particular species.
Calculate Simpson’s diversity index for area B (showing your working).
D=
(2 points)
50  49
;
(25  24)  (25  24)
= 2.04;
(ii)
Simpson’s diversity index for area A is 1.38. Suggest a reason for the difference between the values for
these two areas.
(1 point)
there is a difference between the (relative) abundance oforganisms;
one area has been disturbed by human activities;
two areas are at different seral stages; 1 max
Any other reasonable suggestion.
Net primary productivity / g m–2 yr–1
Paper 2 Response – No Points Awarded Practice Only
The graph below shows net primary productivity (NPP) of eight major biomes.
2500
2000
1500
1000
500
0
Tropical Deciduous Tropical Coniferous Agricultural Temperate
grasslands
rainforests
forests
grasslands
forests
land
Tundra
Deserts
Biomes
[D Waugh, Geography An Integrated Approach, (Nelson Thornes Ltd., 2000) p. 304.
Reproduced by permission of Nelson Thornes Ltd.]
(a)
i)
Compare, and give reasons for, the differences in net primary productivity between any two
biomes named in the graph.
(4 points)
For example, comparing tropical rainforest with desert
tropical rainforest has much higher productivity than desert;
year-round growing season in tropical rainforest;
desert – low precipitation, tropical rainforest – high precipitation;
periodicity/unevenness of rainfall;
resulting in lower photosynthesis in desert;
Accept any other reasonable evaluation of the data.
ii)
State two of the main factors which influence productivity.
(2 points)
Award [1] each for any two of the following factors.
precipitation;
temperature;
soil fertility;
light intensity;
altitude;
slope angle;
Accept any other reasonable suggestion.
(b)
4 max
2 max
Explain, with the aid of a diagram, the transfers and transformations of energy as it flows through an
ecosystem.
(7 points)
Award [3 max]for the diagram.
at least three trophic levels identified as storages;
at least three correct flows in correct direction;
completeness i.e. decomposers and/or heat loss included;
heat
solar
insolation
producers
heat
herbivores
heat
carnivores
heat
top
carnivores
heat
decomposers
Award [1] each for any four of the following, [4 max]. Accept any
other reasonable points.
only 10 % of energy available for next trophic level;
primary consumers (herbivores)/secondary consumers (carnivores)/
decomposers;
conversion of light to chemical energy;
re-radiation of heat energy to atmosphere;
loss of radiation through reflection or absorption;
law of conservation of energy/first law of thermodynamics;
7 max
(c)
Compare the structure and distribution of tropical rainforests and tundra.
(4 points)
Award [2 max] for structure, [2 max] for distribution.
Tundra
Rainforest
single layer of vegetation
simplicity
high latitude
less affected by human activities
many layers;
complexity;
low latitude;
reduced and fragmented by human activities;
A table format is not required but each comparison made must
have a statement about each region to gain the mark.
4
Expression of ideas (3)