Past Year DB014 Ecology Answer

TOPIC : ECOLOGY

1 a Sunlight
b Plants: Producer
Birds: Herbivore
Eagle: Carnivore
C Plants Grasshoppers Birds Snakes Eagle
Plants Rats Birds Snakes Eagle
d Eagle
e Eagle, birds, eagle


2) FIGURE 3 represents a food web consisting of several food chains in a particular
ecosystem.
The arrows show the direction of energy flow.























a) State the type of food chain that constitutes the above food web.
Grazing food chain
[1 mark]
b) i) What is autotroph?

An organism that obtains organic food/sugar by synthesizing them from inorganic
materials
[1 mark]
ii) Name the trophic level occupied by the autotroph in the above food web?
First trophic level.
[1 mark]


c) The formation of new tissue by autotroph does not utilize all of the absorbed sunlight.
State two reasons for the loss of energy at this level.
Some of energy reflected/ used in transpiration

Lost by respiration
Lost in excretion

[2 marks]

d). i) State the number of trophic levels for the above food web.

Four
[1 mark]


3) FIGURE 3 shows the energy flow in a forest ecosystem. All values given in parentheses
-2
-1
are in kJ m yr .
























a)
How many trophic levels are involved in the energy flow?

Four

[1 mark]
b) Name the process involved in biomass production in the autotroph?

Photosynthesis

[1 mark]
c) What is another name for autotroph?

Producer
[1
mark]


d) Give ONE example each for biotic factor and abiotic factor that influence energy

flow.

i) Biotic factor :Consumer
ii) Abiotic factor : Climate / soil / Sun
[2 marks]


e) Name TWO processes involved in the release of carbon dioxide into atmosphere.

Respiration

Burning
Decomposition
[2
marks]
f) Give ONE example for each of the following:

Detritivore : Earthworm / Snail / Nematode / Crab / Shrimp
Decomposer : Bacteria / Fungi
[2 marks]



. 4. FIGURE 4 shows three zones X,Y and Z of a deep freshwater lake.


























FIGURE 4

(a) Name X, Y and Z.
X: Littoral
Y: Limnetic

Z: Limnetic / Profundal

[3 marks]
(b) State ONE example of primary consumer in zone Y.

Zooplankton
[1 mark]



(c) (i) What happen to the photosynthesis rate in zone Y as it gets deeper?
Decrease as amount of sunlight penetration become less

[2 marks]



(d) What is the energy source for organism in zone Z and where does it come from?

Energy from organic matter / dead organism

Come from littoral/X and limnetic/Y zones
[2 marks]



(e) Zone Z does not exist in shallow lakes. Why?

Sunlight reaches all the way to the bottom of the lakes (if students answer profundal

zone in question 4(a))
[1mark]



5. FIGURE 3A shows a type of food chain in a particular ecosystem.

























i) State the type of food chain. [1 mark]

Grazing food chain



ii) How many trophic levels are there in the food chain? [1 mark]

Four



iii) Name ONE group of organism that acts as decomposer. [1 mark]

Fungi / Bacteria



iv) Give TWO reasons why sunlight energy absorbed by autotrophs is not totally utilized
to build a new tissues?

[2 marks]
Energy is used in transpiration

Energy is used for cellular respiration

v) Why is food web more realistic compared to food chain? [1 mark]
Some organism can occupy more than one trophic level



6. FIGURE 4 shows a food web in a sea ecosystem.

























a) Name ONE secondary consumer in this food web. [1 mark]

Salmon



b) Based on food web in FIGURE 4, draw a food chain that consists only four trophic
levels. [1 mark]

Rumpai laut dan plankton/Weed & Plankton Shellfish Salmon Shark



c) Sea lice can damage the salmon’s skin, while wrasse is a small fish which feeds upon

sea lice. State the relationship between the salmon and the wrasse. [1 mark]

Mutualism



d) A disease killed most of the salmon in the sea. What will happen to the number of
wrasse? Why ? [2 marks]

Decrease
Because no of sea bird and sea lice as food source that consume by Wrasse is decline.

7. FIGURE 1 shows the zonation of a lake ecosystem.






















a) Name the zones label A, B and C. Give examples of organisms living in each zone.

[6 marks]

Zone Example of organism
A : Littoral zone Rooted plant

B : Limnetic zone Phytoplanton/ Zooplanton

C : Profundal zone Fish



b) Which is the most fertile zone in the lake ecosystem? Give the reason.

[2 marks]
A.

Has well lit water close to shore has sufficient light penetration as major source of
energy in ecosystem.



c)

i) What is labeled by X? [1 mark]

Compensation point



ii) How does the presence of X affect the lake zonation? [1 mark]

X determine the distribution of producer / phytoplankton / plant that occupy the photic
zone.

8. FIGURE 1 shows the terrestrial ecosystem of a tropical rainforest.



























a) Define ecosystem. [1 marks]
Ecosystem is the community of organism in an area and physical factor/environment

with which those organisms interact.



b) Identify strata W, X and Y. [3 marks]

W : Emergent layer
Y : Herbs layer

Z : Ground layer



c) Describe strata Z. [2 marks]

Strata Z receive dead plant and animal.
Level of decomposition is high.

Dominated by decomposer and detritus



d) State the biotic components in the tropical rainforest. [2 marks]
Plant / Producer

Animal / Consumer



e) What is the role of tropical rainforest in the carbon cycle? [2 marks]

Tropical rainforest captured large amount of CO by photosynthesis due to large
2
number of plant population.
It provides large amount of carbon storage as reservoir available as nutrient.



9. . FIGURE 1 shows a food web.





























FIGURE 1

(a) Suggest ONE organism from FIGURE 1 that represents:
[3 marks]
A producer : Carrot / Grass / Paddy

A primary consumer : Grasshopper / rat / rabbit / bird
A secondary consumer : Fox / Owl / Bird



(b) State the difference between a food web and a food chain.
[2 marks]

Food chain is the pathway for transfer of energy from one trophic level to another while food
web consists of several food chain // Food chain shows linear feeding relationship while food web
shows an interconnected feeding relationship.



(c) What do the arrows in the food web indicate?

[1 mark]
Direction of energy flow


(d) State the types of energy that is channeled through the food web.

[1 mark]

Chemical energy







(e) At each level, part of the energy is lost to the environment. State TWO ways through which

energy is lost at each level of the food web.
[2 marks]

Through respiration
Through excretion



(f) Which population would be increased the most if the owls are eliminated?
[1 mark]

Rat






















































10.

10 (b) (i) I : Combustion / burning
II : Respiration
(ii) Plant / algae / cyanobacteria / Photosynthetic organism
(iii) To return the carbon
To the atmosphere and water / reservoir pool.









11. FIGURE 4 shows parts of the biological nitrogen fixation process in the nitrogen cycle.

FIGURE 4



(a) State the names of

(i) compound N : Ammonium / NH 4 +
(ii) compound M : Decomposing bacteria / fungi // detritivore / decomposer

[2 marks]
(b) (i) State the name of compound O.
Nitrate / NO 3 +



(ii) What is the function of compound O?

As nutrient for plants

[2 marks]






(c) State the processes involved in the formation of compounds

(i) N : Ammonification

(ii) O : Nitrification
[2 marks]



(d) State the names of bacteria

(i) X : Nitrosomonas sp.

(ii) Y : Nitrobactor sp.
[2 marks]
(e) What other organisms can perform the same process as bacteria
(i) X : no answer

(ii) Y : no answer

[2 marks]


12. FIGURE 3 shows summary of a nitrogen cycle.























FIGURE 3
a) (i) State THREE processes involved in S.

Biological (nitrogen fixation)
Industrial / chemical (nitrogen) fixation // Haber process

Natural (nitrogen) fixation / lighting / atmospheric / thunderstorm

[3
marks]

(ii) What is the significance of process S?
To enrich nitrogen source in soil

[1
mark]






b) Name the organism A and B.

Organism A : Nitrosomonas sp.

Organism B : Nitrobacter sp.
[2 marks]

c) Name the substances P and Q.

Substance P : Ammonia / NH // Ammonium ion / NH 4 +
3
Substance Q : Nitrate // Nitrat ion / NO 3 -

[2
marks]

d) Name TWO groups of organism involved in process U.

Saprophytic fungi
Saprophytic bacteria

[2
marks]