MODUL 7
T0PIC : DYNAMIC ECOSYSTEM
Objective question
1 Which of the following organisms is a parasite ?
A C
B D
2 If almost all the snakes in the field are killed because of a disease, which organism in the food chain will immediately increased in number?
A Cats C Caterpillars
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B Eagles D Rats
The following statement is about some organisms in an ecosystem.
The green alga produce food for itself and for the fungus. The alga is also sheltered and protected from drying out by the fungus.
The fungus supplies carbon dioxide and nitrogenous compounds for the alga.
Which of the following interaction best describes the above statement.
A Parasitism C Mutualism
B Competition D Commensalism
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4 Diagram shows a pyramid of numbers of organisms shown in a paddy field with four trophic level.
4
3
2
1
Which of the following sit on the trophic level 4?
A Eagles C Lion
B Snakes D Fish
5 Diagram shows a food web in the forest.
Trees
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Squirrels
Snakes
Beetles
Birds
Rabbits
Caterpillars
Eagles
Which of the following organisms have the lowest population in the forest?
A Trees C Eagles
B Snakes D Rabbits
The following diagram shows the total energy transferred through four trophic levels.
Trees Grasshoppers Birds Snakes
4000 kJ 800kJ 160kJ 32kJ
What percentage of energy is lost from the producer to the tertiary consumer?
A 99% C 80%
B 20% D 10%
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7 Table shows the biomass of a few types of organisms in a community.
Organism Total Biomass of All
Organism at each
P
Q
R
S trophic level(kg)
1200
30
150
670
T
U
100
2700
Which of the following is a possible food chain in this community?
A P → U → S → T C P → S → T → Q
B Q → R → S → P D U → S → P → Q
8 Which of the following are primary consumers ?
A Decomposers C Herbivors
B Autotrophs D Carnivores
9 The picture shows the root structure of a mangrove tree.
In the profile of a mangrove swamp below , which part of the zone can this tree be found?
High tide
Low tide
Zone 1 Zone II Zone III
A Zone I C Zone III
B Zone II D Zone IV
Zone IV
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10 The factors which influence the distribution of organisms in pond include
I the pH
II light intensity
III the presence of predators
IV concentration of carbon dioxide
A I and II C II, III and IV
B I, II and III D I, II and IV
11 The table shows the results of an investigation on the population of rats in a paddy field.
Catch
First
Number of rats caught
300 is marked
Second 80 marked 120 unmarked
What is the estimated population of rats in that area?
A 180 C 450
B 200 D 750
12 A student used quadrat sampling techniques in an experiment to study the coverage of plant
X in a grass field. The student used a quadrat measuring 1m 2 . The table shows the student’s
results.
Quadrat 1 2 3 4 5
Number of speices X
15 14 19
What is the percentage of cover of plant X in the field?
A 46 % C 11∙5%
B 23% D 2∙3 %
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13 Diagram shows a plastic quadrat used to determine the coverage of bread mould on a peace bread. The shaded area shows the present of mould.
Based on the result obtained in the diagram, calculate the percentage of the bread mould , taking the area of on small square to be 1 cm²
A 30 % C 60%
B 40% D 70%
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14 Table below shows stages in the ecological changes that occur in a swamp within a period of time.
S Succession
T Competition
U Formation of climax communities
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V Colonization
What is the correct sequence of the changes that occur?
A T, S, V, U C V, T, S, U
B T, V, S, U D V, S, T, U
15 The graph shows changes in the population of two species of beetles, T and U, over a period of time. Both species feed on the same food source.
T U
Population
What is the interrelationship between species T and U?
A Symbiosis C Parasitism
B Predation D Competition
Which of the following correctly shows the role of useful microorganisms?
I
Microorganisms
Virus
II Bacteria
III Yeast
IV Fungi
Uses
Producing antibiotic
Cleaning of oil spills
Fermentation to produce alcohol
Decomposition in nitrogen cycle
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A I and III C II, III and IV
B I, II and III D I, II, III and IV
Which of the following exits only as an parasites?
A Viruses C Fungi
B Protozoa D Algae
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18 Diagram shows part of the nitrogen cycle.
Plant protein Animal protein
Nitrate
Ammonium compound
Bacteria X
What is bacteria X?
Nitrite
A Rhizobium C Nitrobacter
B Lactobacillus D Nitrosomonas
19 The following information is related to a process occurring in an ecosystem.

The pioneer species is replaced by a new species which is more adapted to the habitat

The process occurs gradually over a long period of time

The process ends with a climax community
The process is
A colonisation C succession
B evolution D competition
20 Which of the following diseases cannot be controlled through vaccination?
I Cold
II Cough
III Measles
IV Poliomielitis
A I and II C II and IV
B III and IV D I, III and IV
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Structure Question
1 Diagram below shows an ecosystem consisting of different flora and fauna and the environment in which they live. a) Abiotic and biotic components influence the lives of all organisms in the ecosystem.
Give two example of biotic and abiotic components in the ecosystem.
Biotic : 1…………………………………………………………………………………….…..
2………………………………………………………………………………………..
Abiotic: 1 ………………………………………………………………………………………..
2……………………………………………………………………………………….
( 2 marks )
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b) Based on the diagram, give an example of the following. a) Producer …………………………………………………………………………………….. b) Primary consumer………………………………………………………………………….. c) Carnivore……………………………………………………………………………………..
(3 marks) c) Based on the ecosystem given, build a food web consisting at least three food chains.
(3 marks) d) Explain the method used to estimate the population size of a species of grass in the
ecosystem.
……………………………………………………………………………………………………….
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(4 marks) e) The grass absorbs 15 000 kJ solar energy. Energy loss at each trophic level is 90%.
Calculate the total energy transferred to the organism in the third trophic level.
(1 mark)
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2 Diagram below shows some parts of the nitrogen cycle.
Nitrogen in the atmosphere
Denitrification
Process X
Plant Protein
Nitrites
Nitrosomonas bacteria
Process Y
DIAGRAM 2 a) i) Fill in the three empty boxes by choosing the correct words from the following list:
Ammonia, Animal protein, Decomposers, Nitrates
(4 marks) ii) Name the process X and Y :
Process X : ……………………………………………………………………………………….
Process Y : ……………………………………………………………………………………....
( 2 marks) b) Give one major function of nitrogen in plants.
………………………………………………………………………………………………………
( 1 mark)
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c) In some plants, nitrogen in the air can be converted into plant protein. Explain how this
happens.
. ………………………………………………………………………………………………………
………………………………………………………………………………………………………
………………………………………………………………………………………………………
………………………………………………………………………………………………………
(3 marks) d) Suggest the effect to the ecosystem if Nitrosomonas sp. has been destroyed or dead .
……………………………………………………………………………………………………….
………………………………………………………………………………………………………
………………………………………………………………………………………………………
(3 marks) e) Name and state the roles of other microorganisms not shown in the above nitrogen cycle.
………………………………………………………………………………………………………
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( 1 mark ) f) What is meant by the term denitrification?
………………………………………………………………………………………………………
………………………………………………………………………………………………………
( 1mark ) g) Some farmers do not use artificial fertilizers to add nitrates into the soil and called as
organic farmers. Explain why organic farmers often grow more peas and beans than other
farmers.
………………………………………………………………………………………………………
………………………………………………………………………………………………………
………………………………………………………………………………………………………
………………………………………………………………………………………………………
( 2 marks)
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3 Diagram below shows a mangrove swamp at a river mouth in 1950 and 2007 respectively. The line XY shows the position of the beach.
Diagram 3.0
DIAGRAM 3 a) i) What has happened to the mangrove zone in diagram 3.
……………………………………………………………………………………………………
( 1 mark)
ii) Name the process that is taking place.
……………………………………………………………………………………………………
(1 mark)
iii) Explain the process mention in (a) ii)
……………………………………………………………………………………………………
……………………………………………………………………………………………………
……………………………………………………………………………………………………
(3 marks)
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b) By using suitable keys, sketch the zones of mangrove swamp in diagram 4 ii) in which
the following mangrove trees can be found.
Brugueira sp, Avicennia sp, Rhizophora sp . (3 marks)
DIAGRAM 3.1 c) i) State the type of seedlings produced by the mangrove trees.
…………………………………………………………………………………………………….
(1 mark)
ii) Explain how this type of seedling increases the chances of survival of the mangrove
trees.
…………………………………………………………………………………………………….
…………………………………………………………………………………………………….
(2 marks) d) State one problem faced by mangrove trees. Explain how mangrove trees overcome this
problem.
……………………………………………………………………………………………………..
……………………………………………………………………………………………………..
( 2 marks )
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1
Section C a) Diagram 1 shows a type of bacteria living in the root nodules of a leguminous plant.
DIAGRAM 1 a) Describe the relationship between the bacteria and the leguminous plant (4 marks) b) Describe how to determine the percentage coverage of lichens on the bark of the tree.
(6 marks) c) Diagram below shows an ecosystem in a pond.
Discuss the flow of energy in the food chain of the ecosystem. (10 marks)
Skema Modul 7 ( Ecosystem Dinamic)
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Section A
1
2
3
4
5
6
7
B
C
A
C
B
D
C
8
9
C
C
10 D
Structure question
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19
20
1a) Temperature, water, soil
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14
15
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D
A
C
C
D
C
A
C
A
A
Either 2
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[ 2 ] b) Producers, consumers c) Eg. Plant/Grass
Snakes
Snails
Grasshopper Zebra Deer
Frog Leopald/Tiger
Bird d) 1. A quadrat is placed randomly at a selected site
2. The grass species between the boundary of quadrat is identified and counted
3. The procedures are repeated at a number of randomly selected sites throughout the ecosystem
4. The density of the species is estimated by using the following formula:
Density = Total number of individuals of a species in all quadrats
Total number of quadrats X area of each quadrat e Primary – 1500kJ
Secondary – 1500kJ
Tertiary – 150kJ
2a)i) Animal protein, Ammonia, Nitrates, Decomposers
I mark for each food chain
[ 3 ]
[ 4 ]
[ 2 ]
[ 4 ]
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b) c) ii) d)
X – Nitrogen fixation
Y – Decomposition
- Nitrogen is the major component of protein in the cell
- The root nodules of the plants such as leguminous plant contain bacteria/
Rhizobium sp e) f) g)
- that are capable of converting atmospheric nitrogen into
complex compounds
- such as nitrates which are then used by the plants to
make protein
- Death of Nitrosomonas bacteria will effect the process of building up of ammonia
- causes the death of nitrobacter bacteria
- which then results with stopping of nitrate production
- Nitrobacter bacteria convert / oxidize nitrite into nitrate
- Denitrifying bacteria – break nitrate into nitrogen,
- saprophytic bacteria/saprophytic fungus
– decompose the protein / organic substance into inorganic substance
- which convert atmospheric nitrogen into nitrate.
3ai) They have been moved from their original position ii) Succession iii) - The roots of the pioneer species trap the mud, causing the soil to become more compact
- At the same time the soil level increases, thereby exposing its exposure to the tides and this makes the soil unsuitable for the pioneer species .
- The species in zone U are the successors , which take over the area of zone T
- Slowly, succession of the species in zone W takes place b
- Denitrification is the process of breaking up nitrate in the soil into nitrogen
gas by the denitrifying bacteria such as Pseudomonas sp.
- More peas and beans are often grown by organic farmers because in the
root nodules of those plants live nitrogen fixing bacteria such as
Rhizobium sp
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○ ○
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∆ ∆ ∆
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○ ci)
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Viviparous seedling
∆
∆
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Brugeira sp Avicennia sp Rhizophora sp
○ ii) - The seedling are able to germinate while still being attached to the parent plant.
○
- As the seedling fall into the water , they can float horizontally and, subsequently, get washed up on mudflats where they settle and grow into new plants d - The mangrove trees are exposed to direct sunlight which results in a high rate of transpiration.
- This problem is overcome by the thick and succulent leaves of mangrove trees which can store water
Essei Question
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[ 3 ]
[ 1 ]
[ 2 ]
[ 2 ]

1a - Nitrogen fixing bacteria such as the Rhizobium sp. Live inside the root nodules of a leguminous plant.
- In this relationship, known as mutualism, both the organisms benefit
- The Rhizobium sp bacteria convert atmospheric nitrogen into ammonia that is used by plant
The plants in turn provide the bacteria with energy-rich sugars b c
- place a quadrat measuring 10 cm XZ 10cm on the bark of the tree
- To estimate the percentage coverage, the number of squares occupied by the lichens are counted and this number is then multiplied by the area of each square
- Each small square of the quadrat represents 1 % coverage or 1 cm
²
of the area.
Only squares that are covered by half or more than half of the spesies are counted
- the square that are covered by less than half of the lichens are not included
- the procedure is repeated by placing the quadrat at different aspects of the tree trunk
- the percentage coverage is calculated by using the following formulae
Percentage coverage = aerial coverage of all quadrats(m
²) X 100% of lichen total number of quadrats sample X quadrat area
- In a pond ecosystem, the source of energy is sunlight
- Producers such as lotus plants and sedges absorb solar energy from the sun and convert it into chemical energy stored in food during photosynthesis
- Some of this energy is used by the lotus plants for cell division, growth and excretion
- When the producers die, the energy becomes available to decomposers such as saprophytic bacteria
- As one organism eats another in the pond, there is a transfer of energy from one consumer to another
- When primary consumers such as mosquito larvae feed on the leaves of the lotus plant, some of the energy stored in the lotus plant is passed on to the mosquito larvae
- About 10% of the plant’s available energy is passed on to the primary consumers
- The primary consumers released energy during respiration , etc and used the energy for growth, movement
- Some of this energy becomes available to the decomposers through excretion and defeacation of the primary consumers
- When the secondary consumers like the small fish eat mosquito larvae, the primary
[ 1 ]
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6 marks
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4 marks
[ 1 ]
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consumers available energy is passed on to the secondary consumers
- The small fish loses energy through respiration, excretion and defeacation
- The small fish is then eaten by the big fish. Energy flows through the food chain in the ecosystem when a consumer eats another organism
- When the mosquito larvae, the big fish and the small fish die, they are decomposed by saprophytic bacteria.
[ 1 ]
[ 1 ]
[ 1 ]
10 marks
(max)
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