Biology MCQs for Class 12 with Answers Chapter 14 Ecosystem

Free PDF Download of CBSE Biology Multiple Choice Questions for Class 12 with Answers Chapter 14 Ecosystem. Biology MCQs for Class 12 Chapter Wise with Answers PDF Download was Prepared Based on Latest Exam Pattern. Students can solve NCERT Class 12 Biology Ecosystem MCQs Pdf with Answers to know their preparation level.

Ecosystem Class 12 Biology MCQs Pdf

1. Which of the following represents the sedimentary type of nutrient cycle?
(a) Nitrogen cycle
(b) Carbon cycle
(c) Phosphorus cycle.
(d) Oxygen cycle

Answer

Answer: c


2. In a pond ecosystem, the food chain starts with
(a) Zooplanktons.
(b) Small insects
(c) Phytoplanktons
(d) Small fishes

Answer

Answer: c


3. The last stable community in succession that is in equilibrium with the environment, is called
(a) serai community
(b) pioneer community
(c) climax community
(d) all of these

Answer

Answer: c


4. Which of the following is a pioneer species in xerarch succession?
(a) Phytoplanktons
(b) Lichens
(c) Bryophytes
(d) Sedges

Answer

Answer: b


5. Which of the following statements is correct for secondary succession?
(a) It begins on a bare rock.
(b) It occurs on a deforested area.
(c) It follows primary succession.
(d) It is similar to primary succession, but has a relatively fast pace.

Answer

Answer: d


6. The sequence of communities of primary succession in water is [NCERT Exemplar]
(a) phytoplankton, sedges, free-floating hydrophytes, rooted hydrophytes, grasses and trees.
(b) phytoplankton, free-floating hydrophytes, rooted hydrophytes, sedges, grasses and trees.
(c) free-floating hydrophytes, sedges, phytoplankton, rooted hydrophytes, grasses and trees.
(d) phytoplankton, rooted submerged hydrophytes, floating hydrophytes, reed swamp, sedges, meadow and trees.

Answer

Answer: d


7. The reservoir for the gaseous type of biogeochemical cycle exists in [NCERT Exemplar]
(a) stratosphere
(b) atmosphere
(c) ionosphere
(d) lithosphere

Answer

Answer: b


8. The process of mineralisation by micro organisms helps in the release of [NCERT Exemplar]
(a) inorganic nutrients from humus
(b) both organic and inorganic nutrients from detritus
(c) organic nutrients from humus
(d) inorganic nutrients from detritus and formation of humus.

Answer

Answer: a


9. Which of the following ecosystems is most productive in terms of net primary production? [NCERT Exemplar]
(a) Deserts
(b) Tropical rain forests
(c) Oceans
(d) Estuaries

Answer

Answer: b


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

Answer

Answer: b


11. Vertical distributioon of different species occupying different levels in an ecosystem, is called _______ .

Answer/Explanation

Answer:
Explaination: Stratification.


12. The rate of production of biomass is termed as _______ .

Answer/Explanation

Answer:
Explaination: Productivity.


13. The degradation of humus by some microbes to release the inorganic nutrients, is called _______ .

Answer/Explanation

Answer:
Explaination: Mineralisation.


14. _______ of organisms is the beginning of the detritus food chain.

Answer/Explanation

Answer:
Explaination: Death.


15. _______ are the saprotrophs (heterotrophs) which meet their energy requirements by degrading the detritus.

Answer/Explanation

Answer:
Explaination: Decomposers.


16. The amount of energy _______ at successive trophic levels.

Answer/Explanation

Answer:
Explaination: Decreases.


17. The _______ is measured as biomass or number per unit area.

Answer/Explanation

Answer:
Explaination: Standing crop.


18. The pyramid of number in a grassland ecosystem is .

Answer/Explanation

Answer:
Explaination: Upright.


19. are the pioneer species in the primary succession on a rock.

Answer/Explanation

Answer:
Explaination: Lichens.


20. The technical term given to nutrient cycles is cycles.

Answer/Explanation

Answer:
Explaination: Biogeochemical.


21. Match the items in Column I with those in Column II.

Column I Column II
A. Standing crop 1. The amount of mineral nutrients in the soil at a given time
B. Standing state 2. Sedementary cycle
C. Climax community 3. Herbivores and carnivores
D. Primary producers 4. In near equilibrium with the environment
E. Phosphorus cycle 5. Mass of living matter in a trophic level at a given time
F. Secondary producers 6. Phytoplanktons
Answer/Explanation

Answer:
Explaination: A – 5, B – 1, C – 4, D – 6, E – 2, F – 3


22. Match the items in Column I with those in Column II.

Column I Column II
A. Pyramid of  energy 1. Phytoplanktons
B. Pyramid of biomass 2. Mesic forest
C. Climax community 3. Upright/inverted
D. Hydrarch succession 4. Always upright
5. Pioneer species
Answer/Explanation

Answer:
Explaination: A – 4, B – 3, C – 2, D – 1


23. Natural or man-made distribances during succession, can convert a particular serai stage to an earlier stage. [True/False]

Answer/Explanation

Answer:
Explaination: True.


24. The pioneer species always remain in equilibrium with the environment and do not change easily. [True/False]

Answer/Explanation

Answer:
Explaination: False.


25. The function of reservoir of any nutrient cycle is to store as much matter as possible. [True/False]

Answer/Explanation

Answer:
Explaination: False.


26. In a hydrarch succession, the marsh-meadow stage is preceded by the scrub stage. [True/False]

Answer/Explanation

Answer:
Explaination: False.


27. In an ecological pyramid, the amount of energy available at the lower trophic level is always more than that at a higher trophic level. [True/False]

Answer/Explanation

Answer:
Explaination: True.


Directions (Q28 and Q29): Mark the odd one in each of the following groups.
28. Phytoplanktons, Zooplanktons, Reed-swamp stage, Lichens.

Answer/Explanation

Answer:
Explaination: Lichens.


29. Fragmentation, Stratification, Leaching, Catabolism.

Answer/Explanation

Answer:
Explaination: Stratification.


30. What is an ecosystem?

Answer/Explanation

Answer:
Explaination: An ecosystem is a functional unit of nature, where biotic components (living organisms) interact among themselves and also with the abiotic environmental or physical factors.


31. What is meant by species composition in an ecosystem?

Answer/Explanation

Answer:
Explaination: Species composition refers to all the plant, animal and microbial species present in a given ecosystem.


32. What is ‘stratification’ in an ecosystem?

Answer/Explanation

Answer:
Explaination: ‘Stratification’ in an ecosystem refers to the vertical distribution of different species occupying different levels.


33. How is ‘ stratification’ represented in a forest ecosystem? [Delhi 2014]

Answer/Explanation

Answer:
Explaination: In a forest, the trees occupy the upper/ topmost vertical strata, the shrubs, the second and herbs, the bottom layers.


34. How is primary productivity in an ecosystem determined? [AI2012C]

Answer/Explanation

Answer:
Explaination: Primary productivity is determined as the amount of biomass or organic matter produced per unit area over a time period by the plants during photosynthesis.


35. GPP – R = NPP
What does ‘R’ represent in the given equation for productivity in an ecosystem? [Delhi 2014C]

Answer/Explanation

Answer:
Explaination: R represents the respiratory losses.


36. What is net primary productivity of an ecosystem? [Foreign 2015]

Answer/Explanation

Answer:
Explaination: Net primary productivity of an ecosystem refers to the biomass available in the producers for consumption by heterotrophs, i.e., herbivores and decomposers.


37. Write the equation that helps in deriving the net primary productivity of an ecosystem. [Delhi 2013]
Or
How is the net primary productivity of an ecosystem derived? [AI 2012C]

Answer/Explanation

Answer:
Explaination: Gross primary productivity (GPP) – Respiratory loss (R) = Net primary productivity (NPP); it is the amount of energy/biomass available in the producers for consumption by herbivores.


38. How is net primary productivity different from gross primary productivity?[AI2012C]
Or
Write a difference between net primary productivity and gross productivity. [AI 2011]

Answer/Explanation

Answer:
Explaination:
Net primary productivity refers to the , biomass/organic matter available at the 1 producer level to the primary consumers,
i.e. GPP – Respiratory losses.
Gross primary productivity is the rate of production of biomass/organic matter by producers during photosynthesis.


39. What is the approximate value of net primary productivity of the biosphere?

Answer/Explanation

Answer:
Explaination: 170 billion tons of (dry weight) organic matter.


40. How much of productivity is contributed by oceans?

Answer/Explanation

Answer:
Explaination: Oceans contribute about 55 billion tons organic matter.


41. Why is the assimilation of energy at the herbivore level, called secondary productivity?

Answer/Explanation

Answer:
Explaination: Herbivores are the primary consumers; the rate of assimilation or formation of new biomass at the consumer level is secondary productivity.


42. All the primary productivity is not available to a herbivore. Give one reason. [HOTS]

Answer/Explanation

Answer:
Explaination: A considerable amount of gross primary productivity is used by the plants in respiration; so not all primary productivity is available for consumers.


43. Name the two climatic factors that regulate decomposition.

Answer/Explanation

Answer:
Explaination: Temperature and soil moisture are the two climatic factors that regulate decomposition.


44. Why is an earthworm called a detritivore? [Foreign 2012]

Answer/Explanation

Answer:
Explaination: Earthworms ingest and breakdown the detritus into smaller particles; hence they are called detritivores.


45. What is meant by PAR?

Answer/Explanation

Answer:
Explaination: The part of the solar radiation which can be absorbed and used by the plants for photosynthesis, is called photosynthetically active radiation (PAR).


46. What are primary carnivores?

Answer/Explanation

Answer:
Explaination: Primary carnivores are the secondary consumers, which depend on the herbivores (primary consumers) for their food needs.


47. What is a detritus food chain made up of? How do they meet their energy and nutritional requirements? [AI 2013]

Answer/Explanation

Answer:
Explaination:
– It is made up of decomposers, i.e. some bacteria and some fungi.
– They meet their energy and nutrient requirements by degrading the dead organic matter or detritus.


48. Name two omnivores that occupy positions in both grazing food chain as well as detritus food chain.

Answer/Explanation

Answer:
Explaination: Cockroaches and crows.


49. Write the basis on which an organism occupies a space in its community/natural surroundings. [Foreign 2010]

Answer/Explanation

Answer:
Explaination: Their feeding relationship with other organisms.


50. Mr Galgotia eats curd/yoghurt. In this case, which trophic level will he occupy? [CBSE Sample Paper 2010; HOTS]

Answer/Explanation

Answer:
Explaination: He occupies third tropic level, i.e., he is a secondary consumer.


51. ‘Man can be primary as well as a secondary consumer.’ Justify this statement. [Foreign 2015]

Answer/Explanation

Answer:
Explaination:
– When man eats plant food, he is primary consumer.
– When he eats meat (animal food), he is a secondary consumer.


52. State what ‘standing crop’ of a trophic level represents. [AI 2013]

Answer/Explanation

Answer:
Explaination: Standing crop of a trophic level represents the amount of living matter (biomass) present at a trophic level at a given time.


53. List any two ways of measuring the standing crop of a trophic level. [Foreign 2010]

Answer/Explanation

Answer:
Explaination:
Standing crop is measured as
(i) biomass, i.e. mass of living organisms in an unit area
(ii) number of organisms in an unit area.


54. How are biomass and standing crop related to each other? [CBSE Sample Paper 2013, 2014]

Answer/Explanation

Answer:
Explaination:
– Biomass is the mass of living organisms or organic matter.
– Standing crop is measured in terms of biomass.


55. Why is measurement of biomass in terms of dry weight more accurate than fresh weight? [HOTS]

Answer/Explanation

Answer:
Explaination: Measurement of biomass in terms of dry weight is more accurate because it avoids variations in weights due to seasonal moisture differences.


56. Define ecological succession.

Answer/Explanation

Answer:
Explaination: Ecological succession is a community controlled phenomenon, in which the structure and composition of communities change in an orderly and sequential manner, leading ultimately to the establishment of a climax community.


57. What is a sere?

Answer/Explanation

Answer:
Explaination: The entire sequence of communities, that successively change in a given area resulting in a climax community, is called a sere.


58. Define climax community.

Answer/Explanation

Answer:
Explaination: The community established at the terminal stage of succession, is called climax community.


59. Mention the role of pioneer species in primary succession on rocks. [Foreign 2012]

Answer/Explanation

Answer:
Explaination: Lichens are the pioneer species in the succession on rocks; they secrete acids to dissolve the rock and help in weathering and soil formation and pave way to bryophytes.


60. In the North East region of India, during the process of jhum cultivation, forests are cleared by burning and left for regrowth after a year of cultivation. How would you explain the regrowth of forest in ecological terms? [HOTS]

Answer/Explanation

Answer:
Explaination: It is secondary succession.


61. Differentiate between standing state and standing crop in an ecosystem. [Foreign 2010]

Answer/Explanation

Answer:
Explaination:
Differences:

Standing State Standing Crop
– Standing state refers to the amount of nutrients such as nitrogen, phosphorus, calcium, etc. present in the soil of an ecosystem at a given time. – Standing crop refers to the amount of biomass or organic matter available at a given trophic level/ecosystem at a given time.
– It is in the abiotic components. – It is in the biotic components.

62. Name the two forms of reservoir of carbon, that regulate the ecosystem carbon cycle.

Answer/Explanation

Answer:
Explaination:
(i) Dissolved carbon in oceans.
(ii) Carbon in fossil fuels.


63. How much of carbon is
(a) fixed in the biosphere through photosynthesis annually?
(b) dissolved in the ocean?

Answer/Explanation

Answer:
Explaination:
(a) 4 × 1013 kg of carbon is fixed annually.
(b) 71% of carbon is dissolved in the ocean.


64. Name the natural reservoir of phosphorus and the form in which it is present.

Answer/Explanation

Answer:
Explaination:
– Rocks are the natural reservoir of phosphorus.
– It is present in the form of phosphates.


65. Who put a price tag for the ecosystem services? What is its value?

Answer/Explanation

Answer:
Explaination:
– Robert Constanza et al have tried to put a price tag. , – It’s estimated to be about 33 trillion US dollars.


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