CBSE Class 12 Biology Ecosystem VBQs

Question. A functional unit of nature, where living organisms interact among themselves and also with the surrounding physical environment is
(a) biosphere
(b) ecosystem
(c) environment
(d) None of these
Answer : B 

Question. The two components of an ecosystem are
(a) plants and animals
(b) weeds, trees, animals and man
(c) energy flow and mineral cycling
(d) biotic and abiotic
Answer : D

Question. Abiotic components refer to
(a) non-living physico-chemical factors
(b) living physico-chemical factors
(c) gases produced by industries
(d) living organisms
Answer : A

Question. Biotic components refer to
(a) gases produced by industries
(b) nutrient-deficient soil
(c) living organisms
(d) fossil fuels
Answer : C

Question. Vertical distribution of different species occupying different levels in a biotic community is known as
(a) divergence
(b) stratification
(c) zonation
(d) pyramid
Answer : B 

Question. Stratification is more pronounced in
(a) tropical rainforest
(b) deciduous forest
(c) temperate forest
(d) tropical savannah
Answer : A

Question. Which one of the following is not a functional unit of an ecosystem?
(a) Energy flow
(b) Decomposition
(c) Productivity
(d) Stratification
Answer : D

Question. Maximum primary productivity of pond is achieved by
(a) phytoplankton
(b) zooplankton
(c) floating plants
(d) red algae
Answer : A

Question. In a pond ecosystem, the autotrophic components are
(a) phytoplanktons
(b) algae
(c) submerged and marginal plants
(d) All of the above
Answer : B 

Question. Primary production is
(a) expressed in terms of weight (gm−2) or energy (kcal m−2)
(b) the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis
(c) Both (a) and (b)
(d) None of the above
Answer : C

Question. The rate of biomass production is
(a) productivity
(b) photosynthesis
(c) respiration
(d) decomposition
Answer : A

Question. In an ecosystem, the rate of production of organic matter during photosynthesis is termed as
(a) net primary productivity
(b) gross primary productivity
(c) secondary productivity
(d) net productivity
Answer : B 

Question. Net primary productivity is equal to
(a) organic matter synthesised by photosynthesis plus utilisation in respiration and other losses
(b) organic matter synthesised by photosynthesis minus utilisation in respiration and other losses
(c) rate of increase in body weight of producers plus losssuffered through respiration and damages
(d) rate of resynthesis of organic matter by the consumers
Answer : B 

Question. Secondary productivity is rate of formation of new organic matter by
(a) producer
(b) parasite
(c) consumer
(d) decomposer
Answer : C

Question. The rate of decomposition is dependent on ....... .
(a) chemical nature of detritus
(b) temperature and pH
(c) moisture and aeration
(d) All of the above
Answer : D

Question. The organic substances, which decompose slowly are
(a) chitin
(b) lignin
(c) cellulose
(d) All of these
Answer : D

Question. The rate of decomposition is quicker when detritus is rich in
(a) nitrogen and sugar
(b) phosphorus and sugar
(c) calcium and sugar
(d) Both (b) and (c)
Answer : A

Question. Which one of the following processes can slow down the process of decomposition?
(a) anaerobiosis
(b) aerobiosis
(c) photo-oxidation
(d) photophosphorylation
Answer : A

Question. Primary productivity depends upon
(a) availability of nutrients
(b) photosynthetic capacity of plants
(c) Both (a) and (b)
(d) None of the above
Answer : C

Question. Fill up the blanks.
I. Productivity varies in different ecosystems. It is the highest in…A…and lowest in…B….
II. Productivity varies in different seasons. Algal population is low in…C…and high in .…D….
III. …E…is required for higher primary productivity. …F…have the lowest primary productivity as the soil is deficient in moisture.
Choose the correct option for A, B, C, D, E and F.
(a) A–agriculture field, B–forest, C–winter, D–spring, E–Heat, F–Forest
(b) A–forest, B–pond, C–spring, D–summer, E–Rain, F–Forest
(c) A–coral reef, B–desert, C–winter, D–summer, E–Rain, F–Desert
(d) A–desert, B–coral reef, C–summer, D–winter, E–Forest, F–Desert
Answer : C

Question. The process of breaking down complex organic matter into inorganic substances like CO2, water and nutrient is called
(a) humification
(b) mineralisation
(c) decomposition
(d) leaching
Answer : C

Question. Word detritus includes
(a) dead plant parts
(b) remains of animals
(c) animal excretions
(d) All of these
Answer : D

Question. A detritivore is
(a) animal feeding on plant matter
(b) animal feeding on dead and decaying organic matter
(c) a plant feeding on an animal
(d) animal feeding on another animal
Answer : B 

Question. Which of the following is/are example(s) of detritivore?
(a) Millipedes
(b) Earthworm
(c) Fiddler crabs
(d) All of these
Answer : D

Question.  Earthworms are called farmer’s friends because
(a) they help in fragmentation of detritus and loosening of soil
(b) they help in immobilisation of nutrients inside the soil
(c) they reduce the rate of decomposition
(d) Both (b) and (c)
Answer : A

Question. The organisms which physically and chemically break the complex dead organic remains are known as
(a) scavangers
(b) decomposers
(c) Both (a) and (b)
(d) parasites
Answer : B 

Question. In which layer of soil decomposition occurs at maximum rate?
(a) Upper layer of soil
(b) Middle layer of soil
(c) Lower layer of soil
(d) None of these
Answer : A

Question. The products of decomposition process are
(a) humus
(b) inorganic nutrients
(c) organic nutrients
(d) Both (a) and (b)
Answer : D

Question. Breakdown of detritus into smaller particles by detritivores is a process called
(a) humification
(b) fragmentation
(c) mineralisation
(d) catabolism
Answer : D

Question. The term ecosystem was coined by
(a) AG Tansley
(b) E Haeckel
(c) E Warming
(d) EP Odum
Answer : A

Question. The basic categories of ecosystem are
(a) aquatic
(b) terrestrial
(c) Both (a) and (b)
(d) grassland and crop field
Answer : C

Question. Which of the following is an example of man-made ecosystem?
(a) An island
(b) Aquarium
(c) Desert
(d) Forest
Answer : B 

Question. The process by which water soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts is called as
(a) fragmentation
(b) leaching
(c) catabolism
(d) mineralisation
Answer : B 

Question. The enzymatic process by which degraded detritus is converted into simpler inorganic substances is called
(a) catabolism
(b) leaching
(c) mineralisation
(d) fragmentation
Answer : A

Question. The process of accumulation of a dark coloured amorphous substance that is highly resistant to microbial action and undergoes decomposition at an extremely slow rate is called
(a) mineralisation
(b) humification
(c) organisation
(d) transformation
Answer : B 

Question. Humus is
(a) dark coloured amorphous organic matter rich in lignin
(b) dark coloured organic matter rich in cellulose
(c) Both (a) and (b)
(d) red coloured substance rich in iron
Answer : C

Question. The process of mineralisation by microorganisms helps in the release of
(a) inorganic nutrients from humus
(b) both organic and inorganic nutrients from detritus
(c) organic nutrients from humus
(d) inorganic nutrients from detritus and the formation of humus
Answer : A

Question. The climatic factors that regulate soil microbe activities during decomposition are
(a) temperature
(b) soil moisture
(c) Both (a) and (b)
(d) wind
Answer : C

Question. PAR stands for
(a) Photosynthesis Active Reaction
(b) Photosynthesis Absorb Radiation
(c) Photosynthetically Active Radiation
(d) Photosynthetically Active Reaction
Answer : C

Question. Ecosystems need a constant supply of energy
(a) to counteract increasing disorderliness
(b) to counteract decreasing disorderliness
(c) to synthesise molecules
(d) Both (a) and (c)
Answer : B 

Question. In a balanced ecosystem you would expect the biomass of the ......... to be greater than the biomass of any other groups of organisms. The most appropriate word to fill the blank is
(a) producer
(b) primary consumers
(c) secondary consumers
(d) top predators
Answer : A

Question. Which one of the following pairs belongs to the category of primary consumers?
(a) Insects and cattles
(b) Eagle and snakes
(c) Insects and snakes
(d) Snakes and frogs
Answer : A

Question. Identify the food chain. Dead animal→ Blow fly maggots→ Common frog → Snake
(a) Grazing food chain
(b) Detritus food chain
(c) Decomposer food chain
(d) Predator food chain
Answer : B 

Question. Choose the incorrect option.
(a) GFC (Grazing Food Chain) begins with producers at the first trophic level
(b) GFC binds up inorganic nutrients, while detritus chain helps in releasing inorganic nutrients to the cycling pool
(c) Both (a) and (b)
(d) Detritus chain account for less energy flow than grazing food chain
Answer : D

Question. In an ecosystem, organism occupies a specific place in a food chain is called
(a) Branching lines
(b) Progressive straight line
(c) Trophic level
(d) Standing crop
Answer : C

Question. Given flowchart represents grazing and detritus food chain. Grazing food chain: Grass→Rabbit→ Lion Detritus food chain: Dead leaves→ Wood louse→ Black bird The organisms which constitute the first trophic level of the grazing food chain and the detritus food chain are respectively,
(a) grass and dead leaves
(b) grass and wood louse
(c) rabbit and wood louse
(d) rabbit and black bird
Answer : B 

Question. A lion that eats a zebra that ate grass is a
(a) primary producer
(b) primary consumer
(c) secondary consumer
(d) quaternary consumer
Answer : C

Question. All the animals that depend on plants (directly or indirectly) for food are called
(a) decomposers
(b) root feeders
(c) consumers
(d) grazers
Answer : C

Question. Fill up the blanks.
I. Herbivores are also called …A…
II. Secondary consumers are eaten by larger…B….
III. …C…consumer eat the secondary consumers.
IV. Anetwork of manyfood chains is called a…D…. Choose the correct option for A, B, C and D.
(a) A–secondary consumers, B–top predator, C–Quaternary, D–food web
(b) A–primary consumer, B–predators, C–Tertiary consumer, D–food web
(c) A–tertiary consumers, B–natural enemies, C–Primary consumer, D–food web
(d) A–quaternary consumers, B–alligator, C–Top consumer, D–food web
Answer : B 

Question. Frog that feeds on insects, is a
(a) primary consumer
(b) secondary consumer
(c) tertiary consumer
(d) decomposer
Answer : B  

Question. Which element is formed by the weathering of rocks and absorbed by plant from the soil?
(a) Phosphorus
(b) Carbon
(c) Nitrogen
(d) Oxygen
Answer : A

Question. Phosphorus is needed for the production of
(a) DNA and RNA
(b) cellular membranes
(c) bones and teeth
(d) All of these
Answer : D

Question. In the phosphorus cycle, weathering makes phosphate available first to
(a) producers
(b) decomposers
(c) consumers
(d) None of these
Answer : A

Question. The reservoir for the gaseous type of biogeochemical cycle exists in
(a) stratosphere
(b) atmosphere
(c) ionosphere
(d) lithosphere
Answer : B

Question. Which of the following pair is a gaseous type of biogeochemical cycle?
(a) Nitrogen and carbon cycle
(b) Phosphorus and carbon cycle
(c) Nitrogen and sulphur cycle
(d) Sulphur and carbon cycle
Answer : A

Question. In a ……… cycle, the elements returns and is withdrawn from the atmosphere. Most appropriate word to fill the blank is
(a) gaseous
(b) sedimentary
(c) Both (a) and (b)
(d) None of these
Answer : A

Question. The reservoir for the sedimentary cycle exists in
(a) earth’s crust
(b) organic sediments
(c) calcareous sediments
(d) limestone
Answer : A

Question. The total amount of nutrients like carbon, phosphorus, calcium, etc., present in soil at any time is called
(a) standing crop
(b) standing state
(c) nutrient crops
(d) sediment
Answer : B

Question. In an ecosystem, the cycling of nutrient is known as
(a) geological cycle
(b) chemical cycle
(c) geochemical cycle
(d) biogeochemical cycle
Answer : D

Question. In sedimentary nutrient cycling,
(a) the reservoir pool is lithosphere
(b) the sedimentary cycles are less perfect
(c) the withdrawl from reservoir pool is large
(d) All of the above
Answer : D

Question. Which one of the following is not a gaseous biogeochemical cycle in ecosystem?
(a) Oxygen cycle
(b) Phosphorus cycle
(c) Nitrogen cycle
(d) Carbon cycle
Answer : B

Question. What is the reason behind deficit rising in nutrient reservoir?
(a) Due to imbalance in the rate of influx
(b) Due to imbalance in the rate of efflux
(c) Due to imbalance in the rate of influx and efflux
(d) None of the above
Answer : C

Question. Carbon constitutes …… of dry weight of anorgan ism. Most appropriate word to fill the blank is
(a) 49%
(b) 59%
(c) 69%
(d) 39%
Answer : C

Question. …… of the carbon is found dissolved in oceans, which is responsible for its regulation in atmosphere. 
Most appropriate word to fill the blank is
(a) 51%
(b) 81%
(c) 61%
(d) 71%
Answer : A

Question. Which of the following regulates the amount of carbon dioxide in the atmosphere
(a) respiration in animals
(b) respiration in plants
(c) photosynthesis activity of plants
(d) oceanic resesvoir of carbon
Answer : D

Question. What is themediumbywhich carbon cycle takes place?
(a) Through atmosphere
(b) Through ocean
(c) Through living and dead organisms
(d) All of the above
Answer : D

Question. What human activities are responsible to increase the amount of CO 2 in the atmosphere?
(a) Deforestation
(b) Massive burning of fossil fuels
(c) Vehicle used for transport
(d) All of the above
Answer : D

Question. Which of the following factor is contributing to an overload of the carbon cycle?
(a) Photosynthesis
(b) Cellular respiration
(c) Deforestation
(d) Afforestation
Answer : C

Question. The exchange pool in the carbon cycle is
(a) fossil fuels
(b) sedimentary rock
(c) water
(d) atmosphere
Answer : D

Question. Select the incorrect match. AIIMS 2018
I. Sedimentary nutrient cycle–Nitrogen cycle
II. Pioneer species–Lichens
III. Secondary succession–Burned forests
IV. Pyramid of biomass of aquatic ecosystem–Upright
Codes
(a) I and IV
(b) I, II and III
(c) I and III
(d) III and IV
Answer : A

Question. Fill up the blank.
I. Theproductsof ecosystemprocesses are called…A….
II. …B…are the major source of ecosystem services.
III. …C…and his colleagues tried to put price tags on nature’s life support services, which came up toUS …D…a year.
Choose the correct option for A, B, C and D.
(a) A–Ecosystem services, B–Plants, C–Robert Brown,D–31 trillion
(b) A–Ecology services, B–Plants, C–Robert Constanza,D–32 trillion
(c) A–Ecosystem services, B–Forests, C–Robert Constanza, D–33 trillion
(d) A–Ecology services, B–Ponds, C–Robert Brown, D–34 trillion
Answer : C

I. Assertion and Reason
Direction (Q. Nos. 160-168) In each of the following questions, a statement of Assertion (A) is given by corresponding statement of Reason (R). Of the statements, mark the correct answer as
(a) If both A and R are true and R is the correct explanation of A
(b) If both A and R are true, but R is not the correct explanation of A
(c) If A is true, but R is false
(d) If A is false, but R is true

Question. Assertion (A) An ecosystem is an interaction between biotic and abiotic components.
Reason (R) AG Tansley coined the term ecosystem.
Answer : B

Question. Assertion (A) Bacteria and fungi are microconsumers.
Reason (R) Bacteria and fungi use a very little part of living plant and animals.
Answer : C

Question. Assertion (A) Herbivores are also called as first order consumers.
Reason (R) These obtain their food directly from plants.
Answer : A

Question. Assertion (A) A network of food chains existing together in an ecosystem is known as a food web.
Reason (R) An animal like kite cannot be a part of a food web.
Answer : C

Question. Assertion (A) The pyramid of energy is always upright.
Reason (R) The flow of energy is unidirectional.
Answer : A

Question. Assertion (A) The pyramid of number of pond ecosystem is upright.
Reason (R) Phytoplanktons are maximum and secondary consumers are lesser in number.
Answer : A

Question. Assertion (A) Ecological succession can turn a lake into a dryland forest with time.
Reason (R) A bare rock can become a forest through ecological succession.
Answer : B

Question. Assertion (A) Nutrient cycle means the cycling of glucose or reserved food material within the plant body.
Reason (R) Transfer of biogenetic nutrients between living and non-living components is called biogeochemical cycle.
Answer : D

Question. Assertion (A) Oceans act as the global sink for CO 2.
Reason (R) Human activities are increasing CO2 concentration in the air.
Answer : B

II. Statement Based Questions

Question. Consider the following statements.
I. Forest, glassland and desert are examples of terrestrial ecosystem.
II. Pond, lake, wetland, river and estuary are examples of aquatic ecosystem.
(a) Statement I is true, but II is false
(b) Statement I is false, but II is true
(c) Both statements I and II are true
(d) Both statements I and II are false
Answer : C

Question. Consider the following statements.
I. The components of ecosystem do not include decomposition.
II. Decomposers are saprophytic organisms like fungi,bacteria and flagellates especially abundant in the bottom of the pond.
Choose the correct option.
(a) I is true, but II is false
(b) I is false, but II is true
(c) Both I and II are true
(d) Both I and II are false
Answer : B

Question. Consider the following statements.
I. Producers are also called as transducers because they are able to change radiant energy into chemical form.
II. Consumers are animals, which feed on other organisms or their parts.
III. Decomposers are saprotrophs, which feed on dead bodies of organisms.
Which of the statements given above are correct?
(a) I, II and III
(b) I and II
(c) I and III
(d) II and III
Answer : A

Question. Select the true statements.
I. Productivity can be divided into gross primary productivity and net primary productivity.
II. Net primary productivity is the available biomass for the consumption to heterotrophs.
III. Net primary productivity is equal to gross primary productivity minus respiration.
IV. There is unidirectional movement of energy towards higher trophic levels and its dissipation and loss as heat to the environment.
Choose the correct option.
(a) I, II and III
(b) I and IV
(c) II and III
(d) I, II, III and IV
Answer : D