TEST 9 ANSWERS (F4 C8)
YEAR 2003
1.
Which of the following organisms is a saprophyte?

2.
Figure shows a pyramid of numbers. Which of the following is not true about the organisms in the pyramid in figure
above?
A
B
C
D
3.
What is the correct sequence of ecological change that occurs to a barren
land over a long period of time?
A
Colonization, climax community, succession
B
C
Succession, colonization, climax community
Colonization, succession, climax community
D
Succession, climax community, colonization
4.
Which organism is classified in the Prokaryote kingdom?

5.
Table shows the results of an experiment to study the population of garden
snails in a vegetable farm.
What is the approximate population of the snails in the farm?
A
B
6.
125
320
C
D
330
520
Figure shows a dichotomous key for animals.
Which of the
following is most probably P. Q, R and S?
A
B
C
D
P
Garden snail
Squid
Garden snail
Squid
Q
Squid
Snake
Earthworm
Squid
R
Cockroach
Ant
Prawn
Cockroach
S
Earthworm
Prawn
Snake
Earthworm
7.
Figure shows a mangrove swamp at the mouth of a river in the year 1970.
Which of the following would represent the possible zonal shift at the river mouth in the year 2010?


YEAR 2004
1. The picture shows the root structure of a mangrove tree.
What is the structure Q?
A
B
2.
Knee root
Buttress root
C
D
Fibrous root
Stilt root
The figure shows the effect of interaction between two organisms, P and Q.
Q
What type of interaction is this?
A
B
C
D
3.
Parasitism
Mutualism
Saprophytism
Commensalism
The figure represents a pyramid of numbers of a vegetable farm. P,Q, R and 5 represent the different organisms in
the pyramid of numbers.
An insecticide was used to eliminate the population of Q. Which of the following represents the pyramid of numbers
after the insecticide was used?

YEAR 2005
1.
The diagram shows the feeding method of organism X.
What is the feeding method of organism X?
A
B
C
D
2.
Holozoic
Parasitic
Saprophytic
Autotrophic
A former mining ground can form a primary forest.
Which of the following sequences is correct in the formation of the primary
forest?
A
B
C
D
Successor, climax community, pioneer
Pioneer, climax community, successor
Successor, pioneer, climax community
Pioneer, successor, climax community
3.
The table shows the result of a study on the population of garden snails in a vegetable garden.
The estimated population size of the garden snails is
A
B
20
125
C 320
D 520
YEAR 2006
1.
Diagram shows part of the nitrogen cycle.
Name bacteria X.
A
B
2.
Rhizobium
Lactobacillus
C Nitrobacter
D Nitrosomonas
Diagram shows a crab with barnacles on its shell.
What is the interaction between the crab and the barnacles?
A
B
Parasitism
Mutualism
C
D
Saprophytism
Commensalism
3.
The following information is about a habitat.
Which of the following is the most suitable method to use to estimate the
population of woody plants in the habitat?
A
B
4.
Quadrate of size 1 m x 1 m
Quadrate of size 5 m x 5 m
C
D
Line transect
Belt transect
The following information is related to a process occurring in an ecosystem.



The pioneer species is replaced a new species in more adapted to the
habitat
The process occurs gradually over a long of time
The process ends with a climax community
The process is
A
colonization
C
succession
B
competition
D
evolution
YEAR 2007
1. Diagram shows an interaction between two organisms.
What type of interaction is this?
A
B
Commensalism
Mutualism
C Parasitism
D Saprophytism
2. Which of the following is the correct sequence in the process of plant succession in a pond?

3.
Diagram shows three types of plants, P, Q and R, found in a mangrove swamp
area.
What are plants P, Q and R?
A
B
C
D
4.
P
Avicennia sp.
Rhizophora sp.
Bruguiera sp.
Bruguiera sp.
Q
Rhizophora sp.
Bruguiera sp.
Avicennia sp.
Rhizophora sp.
R
Bruguiera sp.
Bruguiera sp.
Rhizophora sp.
Avicennia sp.
Which of the following describes a habitat?
A The function of an organism in an ecosystem
B The natural surroundings where organisms live
C Different species which live together in an ecosystem
D Several species of organisms which live together in the same place
5.
A student carried out a study on the population of grass P in the schools field. He used the quadrat sampling
technique in the study. Table below shows the result of the study.
The percentage coverage of grass P in the schools field is
A
B
22.7%
37.8%
C
D
2.27%
3.78%
YEAR 2008
1. Table 3 shows the number of plant P present in 10 different quadrates, each measuring
1 m x 1 m.
Quadrat number
I
II
III
IV
V
VI
VII
VIII
IX
X
Number of plant P
14
10
0
22
18
16
12
0
15
13
Calculate the density of P.
A
B
8m-2
12m-2
C 15 m-2
D 120 m-2
2. Diagram 13 shows an interaction between two marine animals.
What is the type of interaction between the organisms?
A
Parasitism
B
Prey-predator
C
D
Saprophytism
Commensalism
3.
Diagram 10 shows a process of colonisation and succession in a pond.
Arrange the diagram in the correct sequence.

YEAR 2005
Section A
1.
P, Q and R in Figure 1 shows three types of interactions between organisms.
(a)(i)
Name the type of interaction represented by P and Q.
P : Mutualism
Q : Commensalisms
[2 marks]
(ii) Describe the interaction represented by P.
 Nitrogen fixing bacteria / Rhizobium in nodules of roots
 Fix the nitrogen into ammonium compounds / ammonia ions
 Rhizobium obtain carbohydrates / shelter / energy from the plant
[3 marks]
(b)(i)
Y?
In the interactions represented by Q and R, what terms are used to describe organisms X and
Organism X : Epiphyte
Organism Y : Saprophyte
[2 marks]
(ii) State one characteristics of organism X that adapts it for the interaction.
Has air root / has false bulb / ability to make its own food without obtaining any
minerals from the trees
[1 mark]
(c)
The rubber tree in the interaction represented by Q dies.
Explain what will happen to organism X.
- X still grow
- because it able to photosynthesize / synthesizes own food
[2 marks]
(d)
.
Saw dust can be used in the interaction represented by R for the commercial cultivation of mushroom.
-
Mushrooms grow on dead organic materials.
Mushrooms secrete enzyme.
Break down complex organic compound into simple product / glucose
[3 marks]
YEAR 2007
Section B
8. The following organisms are found in a paddy field community.
Grasshopper, Paddy plant, Caterpillar, Frog, Owl, Snake, Rat
These organisms interact with each other in the community.
(a) (i) Based on the above organisms, construct:
- A food web showing the interaction of all organisms
 (2)
-
A pyramid of numbers consisting of four trophic levels
 (2)
[4 marks]
(ii) Grasshoppers and caterpillars are pests for paddy plants. How can the population of
grasshoppers and caterpillars be controlled? Explain the impact of the control methods on the paddy
field community.
Criteria
1 : name the method
2 : Impact of control method to the community
Sample answer
Use pesticide  (1)
Kill the pest / grasshopper and caterpillar.  (1)
Accumulation of chemical substances in the surroundings cause water pollution and air
pollution.  (1)
Biological control method.  (1)
Predator kills only the specific pest / grasshopper and caterpillar.  (1)
Causing imbalanced population of the organism in the community.  (1)
[6 marks]
9. (a) Diagram 9.1 shows the process of colonisation and succession in a habitat.
Diagram
9.1
What is meant by “colonisation and succession in a habitat”?
Based on Diagram 9.1, explain how colonisation and succession bring about the
formation of the primary forest in a habitat.
[10 marks]
Sample answer
State the meaning of colonisation and sussession:
Colonisation is a process whereby a species manage to survive in a newly formed area / place.  (1)
Succession is a process when one community changes its environment and causes it to be replaced
by another community.  (1)
[2 marks]
Explain how colonisation and succession bring about the formation of primary forest:
Pioneer species causes changes in the environment in the habitat, make it more suitable for other
species.  (1)
The remains of plants and decayed bodies add nutrients to the soils. Sink and deposited to the bed of
the pond.  (1)
Water level in the ponds decreases.  (1)
Floating plants block the sunlight from reaching the submerged plants in the pond.  (1)
Less photosynthesis for the submerged plants, more dies off.  (1)
Floating plants (successors) replace the submerged plants.  (1)
The successors caused the changes in the habitat.  (1)
The succession process continues, the floating plants are replaced by the emergent plants.  (1)
Finally, the emergent plants are gradually replaced by woody plants which dominates the habitat. The
pond disappears. Primary forest is formed.  (1)
Maximum : 8 marks
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CHAPTER 8 : DYNAMIC ECOSYSTEM
2005
-
2006
-
2007
-
2008
 (1)
1. Pleurococcus sp. is a unicellular green alga found on the bark of trees. The population distribution of
Pleurococcus sp. is affected by abiotic factors such as light intensity.
A group of students carried out an experiment to investigate the effect of light intensity on the population
distribution of Pleurococcus sp.
Diagram 1 shows a tree trunk on which Pleurococcus sp. was growing.
Two samples of the distribution of Pleurococcus sp., Grid X and Grid Y, were taken. Grid X was placed on the
tree trunk facing east which received more sunlight. Grid Y was placed on the tree trunk facing south which
received less sunlight.
Table 1(a) and Table 1(b) show the total surface area covered by Pleurococcus sp. on Grid X and Grid Y.
Grid
Total surface area covered by Pleurococcus sp.
X
32 – 36 cm2
Table 1 (a)
Grid
Total surface area covered by Pleurococcus sp.
Y
4 - 8 .cm2
Table 1 (a)
(a) Record the total surface are covered by Pleurococcus sp. in the spaces provided in Table
1(a) and Table 1(b).
[3 rnarksj
(b) (i) State two different observations made from the diagrams in Table 1(a) and Table 1(b).
Observation 1:
The total surface area covered by Pleurococcus sp in Grid X is 33 cm2
Observation 2:
The total surface area covered by Pleurococcus sp in Grid Y is 5 cm2
( marks]
(ii) State the inferences from the observations in 1(b)(i).
Inference from observation 1:
In grid X there is a growth of Pleurococcus sp because it receives sunlight.
Inferences from observation 2:
In grid Y there is a growth of Pleurococcus sp because it receives sunlight
[3 marks]
( c ) Complete Table 2 based on this experiment.
Variable
Method to handle the variable
Manipulated variable
Position of the grids (X,Y) / (Pleurococcus
sp.)
Place the grids (on the tree trunk that are)
facing east or south
Responding variable
Total surface area covered by
Pleurococcus sp
Count the number of squares covered with
the Pleurococcus sp in Grid X and Grid Y
Constant variable
1.
2.
3.
4.
Type of tree
Sampling time
Size of grid use
Fixing/placing Grid X and Grid Y at
the same height from the ground
1. Use the same tree to place Grid X
and Grid Y
2. Sampling experiment is carried out
at the same time
3. Using the size for Grid X and Grid Y
4. Placing Grid X and Grid Y at the
same height from the ground
Table 3
(3 marks)
(d) State the hypothesis for this experiment.
When the Pleurococcus sp is facing east, the total surface area covered increases
[3 marksl
(e) (i) Construct a table and record all the data collected in this experiment.
Your table should have the following aspects:
 Title with correct unit
 Position of the grid
 Total surface area covered by Pleurococcus sp.
(3 marks)
Position of grid
Total surface area covered by Pleurococcus sp./cm2
X
32 – 36
Y
4-8
(ii) Use the graph paper provided to answer this question. The population of Pleurococcus sp. is represented
by the total surface area covered in the grid. Using the data in 1(e)(i), draw a bar chart to show the relationship
between the population of Pleurococcus sp. and the position of the grids.
Population of Pleurococcus sp./cm2
40
30
20
10
0
X
Y
Position of the grid
(f) Based on the bar chart in I(e)(i), explain the relationship between the population distribution of Pleurococcus
sp. and the light intensity.
The population of Pleurococcus sp. is greater for Grid X which receives high light intensity
[3marks]
(g) State the operational definition for population distribution of Pleurococcus sp.
Population distribution is defined as the total surface area covered by Pleurococcus sp. within a 10
cm x 10 cm (or 100 cm2) grid at different (compass) directions
[3 marks]
(h) Lightning strikes the tree and causes the tree to fall. The Pleurococcus sp. under study is then exposed to
direct sunlight from 7.00 a.m. till 6.00 p.m. daily.
Based on the results of this experiment, predict what will happen to the total surface area covered by the
Pleurococcus sp. after one week.
Explain your prediction.
Size of the total surface area covered by Pleurococcus sp increases because there is more light
intensity and more photosynthesis will take place.
[3 marks]
(i) The following is a list of biotic and abiotic factors.
pH paper, fish, waterlily, humidity, snail, temperature, soil
Classify these factors in Table 3.
Biotic factors
Abiotic factors
Fish
Waterlily
Snail
pH
Humidity
Temperature
Soil