MCQ Questions for Class 12 Biology: Ch 14 Ecosystem

MCQ Questions for Class 12 Biology: Ch 14 Ecosystem

1. If we completely remove the decomposers from an ecosystem, its functioning will be adversely affected, because
(a) energy flow will be blocked
(b) herbivores will not receive solar energy
(c) mineral movement will be blocked
(d) rate of decomposition will be very high
► (c) mineral movement will be blocked

2. Which one of the following is a denitrifying bacterium?
(a) Pseudomonas
(b) Escherichia coli
(c) Nitrobacter
(d) Nitrosomonas
► (a) Pseudomonas

3. The common nitrogen-fixer in paddy fields is
(a) Rhizobium
(b) Azospirillum
(c) Frankia
(d) Oscillatoria
► (b) Azospirillum

4. Flow of energy in our ecosystem takes place :
(a) only in one direction
(b) possible in two directions
(c) in three dimensions
(d) may occur in multiple directions
► (a) only in one direction

5. River water deposits
(a) loamy soil
(b) alluvial soil
(c) laterite soil
(d) sandy soil
► (b) alluvial soil

6. During adverse season, therophytes survive by
(a) bulbs
(b) corms
(c) rhizomes
(d) seeds
► (d) seeds

7. Breakdown of detritus by microbial enzymes into simple forms is called?
(a) Mineralization
(b) Fragmentation
(c) Catabolism 
(d) Leaching
► (b) Fragmentation

8. Which one of the following is the most important service provided by ecosystems?
(a) soil formation
(b) aesthetic values
(c) pollination
(d) water purification
► (a) soil formation

9. In a biotic community, the most important factor for survival of an animal is
(a) day length
(b) soil moisture
(c) green food
(d) predators
► (c) green food

10. In a biotic community, the primary consumers are 
(a) carnivores
(b) omnivores
(c) detritivores
(d) herbivores
► (d) herbivores

11. The pyramid which cannot be inverted in a stable ecosystem is that of
(a) Biomass
(b) Number
(c) Energy
(d) All the above
► (c) Energy

12. Which of the following pairs is a sedimentary type of biogeochemical cycle?
(a) oxygen and nitrogen
(b) phosphorus and sulphur
(c) phosphorus and nitrogen
(d) phosphorus and carbon dioxide
► (b) phosphorus and sulphur

13. Which one of the following ecosystem types has the highest annual net primary productivity?
(a) tropical deciduous forest
(b) temperate evergreen forest
(c) temperate deciduous forest
(d) tropical rain forest
► (d) tropical rain forest

14. 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)
► (c) Gross Production (GP)

15. Which of the following is the most stable ecosystem?
(a) Forest
(b) Desert
(c) Mountain
(d) Ocean
► (d) Ocean

16. What is true of ecosystem?
(a) Primary consumers are least dependent upon producers
(b) Primary consumers out - number producers
(c) Producers are more than primary consumers
(d) Secondary consumers are the largest and most powerful
► (c) Producers are more than primary consumers

17. Conditions favouring decomposition are:
(a) high temperature and intermediate humidity
(b) low temperature and low humidity
(c) low temperature and high humidity
(d) high temperature and low humidity
► (a) high temperature and intermediate humidity

18. Which of the following ecosystems has highest rate of gross primary production?
(a) Grasslands
(b) Mangroves
(c) Equatorial rain forest 
(d) Coral reefs
► (d) Coral reefs

19. Which of the following ecological pyramid is always erect and upright?
(a) Pyramid of biomass
(b) Pyramid of energy
(c) Pyramid of number
(d) None of these
► (b) Pyramid of energy

20. The greatest biomass of autotrophs in the oceans is that of
(a) sea grasses and slime moulds
(b) free floating microalgae, cyanobacteria and nanoplankton
(c) benthic brown algae,coastal red algae and daphnids
(d) benthic diatoms and marine viruses
► (b) free floating microalgae, cyanobacteria and nanoplankton

21. In an ecosystem, which one shows one-way passage
(a) free energy
(b) carbon
(c) nitrogen
(d) potassium
► (a) free energy

22. Pedology is science of
(a) earth
(b) soil
(c) diseases
(d) pollution
► (b) soil

23. If by radiation all nitrogenase enzymes are inactivated, then there will be no
(a) fixation of nitrogen in legumes
(b) fixation of atmospheric nitrogen
(c) conversion from nitrate to nitrite in legumes
(d) conversion from ammonium to nitrate in soil
► (a) fixation of nitrogen in legumes

24. Forest controls drought through
(a) Functioning as water shed.
(b) Lot of water plant
(c) Retention of water and prevention of soil erosion.
(d) Increasing rainfall
► (d) Increasing rainfall

25. A biome is
(a) Sum of all ecosystems on the Earth
(b) Biotic components in a population
(c) Sum of ecosystems in a geographical area
(d) Biotic components in an ecosystem
► (c) Sum of ecosystems in a geographical area

26. The slow rate of decomposition of fallen logs in nature is due to their
(a) low cellulose content
(b) poor nitrogen content
(c) anaerobic environment around them
(d) low moisture content
► (d) low moisture content

27. Mass of living matter at a trophic level in an area at any time is called
(a) standing crop
(b) deteritus
(c) humus
(d) standing state
► (a) standing crop

28. Approximately how much of the solar energy that falls on the leaves of a plant is converted to chemical energy by photosynthesis?
(a) Less than 1%
(b) 2-10%
(c) 30%
(d) 50%
► (b) 2-10%

29. Available organic matter for herbivores is represented by:
(a) Secondary productivity
(b) GPP
(c) NPP
(d) All the the above
► (c) NPP

30. Correct decreasing order for rate of primary productivity on land will be :
(a) Tropical rainforests >Savannah > Arid regions>Temperate forests
(b) Temperate forests > Tropical rainforests > Savannah > Arid regions
(c) Tropical rainforests > Temperate forests > Savannah > Arid regions
(d) Savannah > Temperate forests > Tropical rainforests > Arid regions
► (c) Tropical rainforests > Temperate forests > Savannah > Arid regions

31. The decomposition of organic matter is brought about by
(a) Protozoans
(b) Plants
(c) Microorganisms
(d) None of the above
► (c) Microorganisms

32. In which of the following places, succession will occur in short time?
(a) on a bare rock
(b) in heavily overgrazed pasture
(c) in a small oligotrophic lake
(d) area exposed by a retreating glacier
► (b) in heavily overgrazed pasture

33. Sudden mass killing of fishes is likely in
(a) mesotrophic lake
(b) oligotrophic lake
(c) salt lake
(d) eutrophic lake
► (d) eutrophic lake

34. 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
► (a) net primary productivity
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