BIOLOGY XII
CHAPTER: ECOSYSTEM
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PART A
1. Which of the following ecosystem has the highest gross primary productivity?
A) Mangroves 

B) Rainforest

 C) Grassland 

D) Coral reef

2. In an ecosystem the rate of production of organic matter during photosynthesis is termed as
A) secondary productivity

 B) net productivity
C) net primary productivity

 D) gross primary productivity

3. Which one of the following types of organisms occupy more than one trophic level in a pond ecosystem?
A) Fish 

B) Zooplankton 

C) Frog 

D) Phytoplankton

4. Of the total incident solar radiation, the proportion of PAR is
A) about 70% 

B) about 60% 

C) less than 50% 

D) more than 80%

5. In a terrestrial ecosystem such as forest, maximum energy is in which trophic level?
A) T3 

B) T4 

C) T1 

D) T2

6. If we completely remove the decomposers from an ecosystem, its functioning will be adversely affected, because
A) mineral movement will be blocked
B) the rate of decomposition will be very high
C) energy flow will be blocked
D) herbivores will not receive solar energy

7. During ecological succession
A) the numbers and types of animals remain constant
B) the changes lead to a community that is in near equilibrium with the environment and is called pioneer community
C) the gradual and predictable change in species composition occurs in a given area
D) the establishment of a new biotic community is very fast in its primary phase

8. An ecosystem which can be easily damaged but can recover after some time if damaging effect stops will be having
A) low stability and high resilience 

B) high stability and low resilience
C) low stability and low resilience 

D) high stability and high resilience

9. Which of the following would appear as the pioneer organisms on bare rocks?
A) Mosses 

B) Green algae 

C) Lichens 

D) Liverworts

10. The dominant second trophic level, in a lake ecosystem, is
A) phytoplankton 

B) zooplankton 

C) benthos

 D) plankton

11. When man eats fish which feeds on zooplanktons which have eaten small plants, the producer in this chain is
A) small plants

 B) fish 

C) man 

D) zooplankton

12. Bamboo plant is growing in a fir forest then what will be the trophic level of it?
A) First trophic level (T1)

 B) Second trophic level (T2)
C) Third trophic level (T3)

 D) Fourth trophic level (T4)

13. Which ecosystem has the maximum biomass?
A) Grassland ecosystem

 B) Pond ecosystem
C) Lake ecosystem

 D) Forest ecosystem

14. The rate of formation of new organic matter by rabbit in a grassland, is called
A) net productivity 

B) secondary productivity
C) net primary productivity

 D) gross primary productivity

15. Vertical distribution of different species occupying different levels in a biotic community is known as
A) zonation 

B) pyramid

 C) divergence

 D) stratification

16. Mass of living matter at a trophic level in an area at any time is called
A) standing crop 

B) detritus 

C) humus

 D) standing state

17. Identify the likely organisms (1), (2), (3) and (4) in the food web shown below.

P) (1) -Deer; (2) – Rabbit; (3) – Frog; (4) – Rat
Q) (1) – Dog; (2) – Squirrel; (3) – Bat; (4) – Deer
R) (1) – Rat; (2) – Dog; (3) – Tortoise; (4) – Crow
S) (1) – Squirrel; (2) – Cat; (3) – Rat; (4) – Pigeon
A) A 

B) B

 C) C 

D) D

18. What type of ecological pyramid would be obtained with the following data?
Secondary consumer: 120 g
Primary consumer: 60 g
Primary producer: 10 g
A) Inverted pyramid of biomass 

B) Pyramid of energy
C) Upright pyramid of numbers 

D) Upright pyramid of biomass

19. The slow rate of decomposition of fallen logs in nature is due to their
A) anaerobic environment around them

 B) low cellulose content
C) low moisture content 

D) poor nitrogen content

20. Energy transfer from one trophic level to other, in a food chain, is
A) 10% 

B) 20% 

C) 1% 

D) 2%

21. Natural reservoir of phosphorus is
A) rock 

B) fossils 

C) sea water 

D) animal bones

22. In a biotic community, the primary consumers are
A) detritivores 

B) herbivores

 C) carnivores 

D) omnivores

23. The rate at which light energy is converted into chemical energy of organic molecules is the ecosystem’s
A) net secondary productivity 

B) gross primary productivity
C) net primary productivity 

D) gross secondary productivity

24. Which one of the following statements for the pyramid of energy is incorrect?
A) Its base is broad
B) It shows energy content of different trophic level organisms.
C) It is inverted in shape.
D) It is upright in shape

25. Which one of the following statements is correct for secondary succession?
A) It begins on a bare rock.
B) It occurs on a deforested site.
C) It follows primary succession.
D) It is similar to primary succession except that it has a relatively fast pace

26. Which one of the following animals may occupy more than one trophic levels in the same ecosystem at the same time?
A) Sparrow

 B) Lion

 C) Goat

 D) Frog

27. The biomass available for consumption by the herbivores and the decomposers is called
A) net primary productivity 

B) secondary productivity
C) standing crop 

D) gross primary productivity

28. Which one of the following is not a functional unit of an ecosystem?
A) Energy flow 

B) Decomposition 

C) Productivity 

D) Stratification

29. The breakdown of detritus into smaller particles by earthworm is a process called
A) humification 

B) fragmentation
C) mineralization 

D) catabolism

30. Which of the following is expected to have the highest value (gm/m2/yr) in a grassland ecosystem?
A) Secondary production 

B) Tertiary production
C) Gross production (GP)

 D) Net production (NP)

31. Which decomposers is/are abundant in the bottom of the pond?
a) Only fungi 

b) only bacteria

 c) only flagellates 

d) All of these

32. Energy in ecosystem always unidirectional movement of from lower trophic level to higher trophic levels due to
a) decrease in size of organisms 

b) decrease feeding habit
c) energy loss as heat to the environment 

d) None of these

33. Choose incorrect about decomposition
a) It is largely an oxygen-requiring process.
b) It is not controlled by chemical composition of detritus.
c) It is not controlled by climatic factors.
d) All of these

34. Identify correct about standing crop of an ecosystem
a) It is mass of living material at a particular time of particular trophic level
b) It is measured as the mass of living organisms.
c) It is measured as the number of organisms in unit area.
d) All of these

35. Which of the ecosystem do not follow the below pyramid pattern?

a) Grassland ecosystem- Pyramid of number
b) Pond ecosystem- Pyramid of number
c) Grassland ecosystem-Pyramid of energy
d) None of these

PART- B

36. Which one of the following is not used for construction of ecological pyramids?
A) Fresh weight 

B) Dry weight
C) Number of individuals

 D) Rate of energy flow

37. Food chain in which microorganisms’ breakdown the food formed by primary producers is
A) parasitic food chain 

B) detritus food chain
C) consumer food chain 

D) predator food chain

38. About 70% of total global carbon is found in
A) oceans 

B) forests

 C) grasslands

 D) agroecosystems

39. Pyramid of numbers in a grassland/tree ecosystem is
A) always inverted 

B) always upright
C) both (A) and (B)

 D) spindle-shaped

40. Which of the following acts as “nature’s scavengers”?
A) Insects 

B) Microorganisms

 C) Man 

D) Animals

41. The primary succession refers to the development of communities on a
A) forest clearing after devastating fire
B) newly-exposed habitat with no record of earlier vegetation
C) freshly cleared crop field
D) pond, freshly filled with water after a dry phase

42. If 2000 J of energy is trapped at producer level, then how much energy will be available to peacock as food in the following chain?
Plant → Mice → Snake → Peacock
A) 2 J 

B) 0.2 J 

C) 20 J 

D) 0.002 J

43. Which of the following ecological pyramids is generally inverted?
A) Pyramid of biomass in a sea 

B) Pyramid of numbers in grassland

C) Pyramid of energy 

D) Pyramid of biomass in a forest

44. Which one of the following is a characteristic feature of cropland ecosystem?
A) Absence of weeds 

B) Ecological succession
C) Absence of soil organisms 

D) Least genetic diversity

45. Pyramid of numbers in a pond ecosystem is
A) irregular

 B) inverted

 C) upright

 D) spindle shaped

46. Pick up the correct food chain.
A) Grass → Chameleon → Insect → Bird
B) Grass → Fox → Rabbit → Bird
C) Phytoplankton → Zooplankton → Fish
D) Fallen leaves → Bacteria → Insect larvae

47. Which of the following is the most stable ecosystem?
A) Mountain

 B) Ocean 

C) Forest 

D) Desert

48. Which one of the following processes during decomposition is correctly described?
A) Catabolism – Last step in the decomposition under fully anaerobic condition
B) Leaching – Water soluble inorganic nutrients rise to the top layers of soil
C) Fragmentation – Carried out by organisms such as earthworm
D) Humification – Leads to the accumulation of a dark colored substance humus which undergoes microbial action at a very fast rate

49. In most ecosystems, all the pyramids, of number, of energy and biomass are upright due to
a) Producers are more in number and biomass than the herbivores,
b) Herbivores are more in number and biomass than the carnivores
c) Energy at a lower trophic level is always more than at a higher level.
d) All of these

50. Researchers have put an average price tag on the fundamental ecosystems services is
a) US $ 10 trillion a year

 b) US $ 18 trillion a year
c) US $ 33 trillion a year 

d) US $ 66 trillion a year
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ANSWER KEY- ECOSYSTEM
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