CBSE Class 12 Biology Ecosystem MCQs Set 04

Question: The gradual and fairly predictable changes in the species composition of a given area is called :
a) Bioprospecting
b) Biofortification
c) Ecological succession
d) Ecological assessment
Answer: c

Question: During decomposition, humification leads to accumulation of a dark coloured amorphous substance called humus. Which of the following is correct regarding humus?
a) Susceptible to microbial action
b) Undergoes decomposition at an extremely high rate
c) Colloidal in nature
d) It promotes compaction of soil
Answer: c

Question: In an aquatic ecosystem, which type of food chain is the major conduit for energy flow?
a) GFC
b) Parasitic food chain
c) DFC
d) Both 1 and 3
Answer: a

Question: All successions, whether taking place in water or on land, proceed to which climax community?
a) Hydric
b) Xeric
c) Mesic
d) Halophytic
Answer: c

Question: Mass of the living material at a particular time is called standing crop. Biomass of a species is more accurately expressed in terms of
a) Fresh weight
b) Dry weight
c) Both (a) and (b)
d) Kcal m⁻² yr⁻¹
Answer: b

Question: The components of an ecosystem are seen to function as a unit when we consider which of the following aspects?
a) Productivity and decomposition
b) Decomposition and energy flow
c) Productivity and energy flow
d) Productivity, decomposition, energy flow and nutrient cycling
Answer: d

Question: About succession, which of the following statements is correct?
a) In xerosere, xeric conditions progress to hydric conditions
b) In hydrosere, mesic environment progresses to hydric conditions
c) In hydrosere, hydric environment progresses to mesic conditions
d) Abandoned farmlands show primary succession
Answer: c

Question: Ecological pyramids show diagrammatic representation of ecological parameters like number, biomass and energy. Which of the following is/are limitations of ecological pyramids?
a) Same species at different trophic levels are not considered
b) Food webs are not accommodated
c) Saprophytes are not given any place
d) All the above
Answer: d

Question: The gradual and fairly predictable changes in species composition of a given area are NOT characterised by
a) Increase in number of species
b) Increase in number of individuals
c) Increase in biomass
d) Decrease in niche specialisation
Answer: d

Question: Amount of biomass or organic matter produced per unit area over a time period by plants is best expressed in terms of
a) Weight (g m⁻² yr⁻¹)
b) Energy (Kcal m⁻² yr⁻¹)
c) Fresh weight
d) Dry weight
Answer: d

Question: About flow of food energy by the process of eating and being eaten, which of the following is incorrect?
a) In aquatic ecosystems, GFC is the major conduit for energy flow
b) In terrestrial ecosystems, DFC is the major conduit for energy flow
c) In predator food chains, organism size increases with trophic level
d) DFC can never be connected with GFC
Answer: d

Question: In an ecosystem based on the production of nearly 6 million plants, how many top consumers can be supported?
a) 708000
b) 354000
c) 3
d) 30000
Answer: c

Question: In an ecosystem, if the dry weight of producers is 809 kg m⁻², the biomass of tertiary consumers will be
a) 37 kg m⁻²
b) 11 kg m⁻²
c) 15 kg m⁻²
d) 1.5 kg m⁻²
Answer: d

Question: How much amount of carbon is fixed in the biosphere through photosynthesis annually?
a) 2 × 10¹³ kg
b) 4 × 10¹³ kg
c) 5 × 10¹³ kg
d) 6 × 10¹³ kg
Answer: b