Ecosystem Class 12 Biology Exam Questions

Please refer to Biology For Ecosystem Class 12 Biology Exam Questions provided below. These questions and answers for Class 12 Biology have been designed based on the past trend of questions and important topics in your class 12 Biology books. You should go through all Class 12 Biology Important Questions provided by our teachers which will help you to get more marks in upcoming exams.

Class 12 Biology Exam Questions Ecosystem

Objective Questions

Question. An ecosystem is a
(a) group of components that interact with one another.
(b) group of interacting species in one place at one time.
(c) biological community and component of the physical environment with which the community interacts.
(d) group of interacting chemicals and their cycles.

Question. Vertical distribution of different species occupying different levels is called
(a) enumeration
(b) stratification
(c) species composition
(d) none of these

Question. In an ecosystem abiotic components includes which of the following ?
(a) Flow of energy
(b) Cycling of materials
(c) Consumers
(d) Flow of energy and cycling of materials

Question. Identification and enumeration of plant and animal species of an ecosystem gives its
(a) productivity
(b) stratification
(c) species composition
(d) all of these

Question. The rate at which light energy is converted into chemical energy of organic molecules is the ecosystem’s
(a) net primary productivity
(b) gross secondary productivity
(c) net secondary productivity
(d) gross primary productivity

Question. What is the annual net primary productivity of whole biosphere?
(a) 170 billion tons (dry weight) of organic matter.
(b) 165 billion tons (dry weight) of organic matter.
(c) 160 billion tons (dry weight) of organic matter.
(d) 155 billion tons (dry weight) of organic matter.

Question. How much portion of the photosynthetically active radiation (PAR) is captured by the plants?
(a) 5 – 10%
(b) 7 – 10%
(c) 8 – 10%
(d) 2 – 10%

Question. Each trophic level has a certain mass of living material at a particular time is known as
(a) catabolism
(b) standing crop
(c) humification
(d) primary productivity

Question. Energy pyramids are used to represent energy transfer in an ecosystem because energy is _______ between each trophic level.
(a) gained
(b) lost
(c) conserved
(d) either conserved or gained

Question. Which one of the following pairs is a sedimentary type of biogeochemical cycle ?
(a) Phosphorus and carbon monoxide
(b) Oxygen and nitrogen
(c) Phosphate and nitrogen
(d) Phosphorus and sulphur

Statement Type Questions

Question. Which one of the following statement is correct about decomposition ?
(a) Decomposition rate is slower if detritus is rich in lignin and chitin, and quicker if detritus is rich in nitrogen and water – soluble substances like sugars.
(b) Decomposition rate is slower if detritus is rich in nitrogen and water – soluble substances like sugars, and quicker if detritus is rich in lignin and chitin.
(c) Decomposition rate is slower if detritus is rich in cellulose, and quicker if detritus is rich in phosphorus.
(d) Decomposition rate is quicker if detritus is rich in lignin, and lower if detritus is rich in sulphur.

Question. Which of the following is not a hypothesis for why foodchain length is limited?
(a) Food-chain length is limited by one organism’s ability to consume another.
(b) Food-chain length is limited because they are easily disrupted by environmental perturbations.
(c) Food-chain length is limited by productivity.
(d) Food-chain length is a function of an ecosystem’s physical structure.

Question. Which statement is true corresponding to the given food chain ?
Grass → Rabbits → Snakes → Hawks
(a) Each predator population has a greater biomass than its prey population.
(b) Each prey population has a greater biomass than its predator population.
(c) Each population is omnivorous.
(d) Each level of food chain returns inorganic nutrients and energy to the producer.

Question. The given statements (i – iv) are the characteristics of productivity.
(i) The rate of biomass production is called productivity and is expressed in terms of a kcal m–2.
(ii) Net primary productivity is rate of production of biomass during photosynthesis.
(iii) Net primary productivity minus respiration loss is called net primary productivity.
(iv) Primary productivity depends only on the plant species inhabiting a particular area.Identify the correct statements.
(a) (i) and (iii)
(b) (ii) and (iii)
(c) (ii), (iii) and (iv)
(d) (ii) and (iv)

Question. Which of following is/are trend(s) in from ecological succession ?
(i) An increase in complexity of species.
(ii) An increase in productivity.
(iii) An increase in community stability and species diversity.
(iv) A decrease in non-living organic materials.
(a) (i) and (iii)
(b) (i) and (iv)
(c) (i), (ii) and (iii)
(d) (i), (ii), (iii) and (iv)

Question. Which of the following include(s) ecosystem services ?
(i) Purification of air and water by forests.
(ii) Forests mitigate droughts and flood.
(iii) Forests act as store house of carbon.
(iv) Forests influence hydrological cycle.
(a) (i) and (iii)
(b) (i) and (iv)
(c) (i), (ii) and (iii)
(d) All of these

Question. Choose the correct statements regarding ecological pyramids.
(i) The relationship between organisms at different trophic levels is expressed in terms of number, biomass and energy.
(ii) Any calculations of energy content, biomass or number has to include one group of organism at that trophic level.
(iii) In most ecosystems, all the pyramids of number, biomass and energy are upright.
(iv) The pyramid of biomass in sea is generally inverted.
(v) Pyramid of energy is always inverted and can never be upright.
(a) (i), (iii) and (iv)
(b) (i)
(c) (ii) and (v)
(d) (i) and (v)

Assertion/Reason Type Questions

In the following questions, a statement of Assertion is followed by a statement of Reason.
(a) If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.
(b) If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.

Question. Assertion : Pyramid of energy may be upright or inverted.
Reason : Only 20% of energy goes to next trophic level.

Question. Assertion : In a food chain, members of successive higher levels are fewer in number.
Reason : Number of organisms at any trophic level depends upon the availability of organisms which serve as food at the lower level.

Question. Assertion : Biotic community has higher position than population in ecological hierarchy.
Reason : Population of similar individuals remains isolated in the community.

Matching Type Questions

Question. Match the following and choose the correct option.

Column – I	Column – II
A. Standing state	I. Nitrogen, Carbon
B. Gaseous cycles	II. Amount of nutrients
C. Standing crop	III. Sulphur, Phosphorus
D. Sedimentary cycles	IV. Living matter at different trophic levels

(a) A – II; B – I; C – IV; D – III
(b) A – I; B – II; C – III; D – IV
(c) A – III; B – II; C – IV; D – I
(d) A – I, B – IV; C – III; D – II

Question. Match the following and choose the correct option.

Column – I	Column – II
A. Pioneer community on	I. Crustose lichens lithosphere
B. Ecological succession	II. Mesophytes
C. Climax community	III. Ecosystem development
D. Ecological pyramid	IV. Elton

(a) A – III; B – II; C – IV; D – I
(b) A – III; B – I; C – IV; D – II
(c) A – I; B – III; C – II; D – IV
(d) A – II; B – III; C – IV; D – I

Question. Which of the following pair is not correctly matched ?
(a) Autotrophs – Fungi
(b) Primary consumers – Zooplankton
(c) Secondary consumers – Fishes
(d) Decomposers – Flagellates

Diagram Type Questions

Question. Refer the given nutrient cycle in a terrestrial ecosystem with few labels marked as A, B, C and D. Identify A, B, C and D.

(a) A – Consumers; B – Decomposition; C – Producers D – Weathering
(b) A – Consumers; B – Weathering; C – Producers; D – Decomposition 
(c) A – Producers; B – Consumers; C – Decomposition; D – Weathering
(d) A – Consumers; B – Producers; C – Decomposition; D – Weathering

Question. Given below is an imaginary pyramid of numbers. What could be one of the possibilities about certain organisms at some of the different levels ?

(a) Level PC is “insects” and level SC is “small insectivorous birds”.
(b) Level PP is “phytoplanktons” in sea and “whale” is on top level TC.
(c) Level PP is “peepal trees” and the level SC is “sheep”.
(d) Level PC is “rats” and level SC is “cats”.

Question. Which of the given pyramids represent the variation in biomass at different trophic levels in pond ecosystem?

Question. The given diagram shows (I, II, III, and IV) the flow of materials between different trophic levels. Which arrow is incorrect?

(a) I
(b) II
(c) III
(d) IV

Critical Thinking Type Questions

Question. In parasitic food chain, the pyramid of number is
(a) linear
(b) upright
(c) inverted
(d) inverted upright

Question. The correct order of the process of decomposition is
(a) Catabolism → Fragmentation → Leaching → Humification → Mineralization
(b) Catabolism →Fragmentation → Humification → Leaching → Mineralization
(c) Fragmentation → Humification → Catabolism → Leaching → Mineralization
(d) Fragmentation → Leaching →Catabolism → Humification → Mineralization

Question. 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

Question. The phosphorus cycle differs from the carbon cycle in that
(a) the phosphorus does not enter living organisms, whereas carbon does.
(b) the phosphorus cycle does not include a gaseous phase, whereas the carbon cycle does.
(c) the phosphorus cycle includes a solid phase, whereas the carbon cycle does not.
(d) the primary reservoir of the phosphorus cycle is the atmosphere, whereas the primary reservoir for the carbon cycle is in rock.

Question. Which of the following could not be considered an ecosystem ?
(a) A small pond
(b) All the fish in a coral reef
(c) Earth
(d) A pile of dung in a pasture

Question. Which of the following contribute(s) to the carbon cycle ?
(a) Respiration and photosynthesis
(b) Fossil fuel combustion
(c) Decompostion of dead organisms
(d) All of these

Question. The primary succession refers to the development of communities on a
(a) freshly cleared crop field.
(b) forest clearing after devastating fire.
(c) pond, freshly filled with water after a dry phase.
(d) newly-exposed habitat with no record of earlier vegetation.

Question. Which one of the following is not used for construction of ecological pyramids?
(a) Number of individuals
(b) Rate of energy flow
(c) Fresh weight
(d) Dry weight

Question. Which one of the following is a primary consumer in maize field ecosystem?
(a) Lion
(b) Grasshopper
(c) Wolf
(d) Phytoplankton

Question. First link in any food chain is a plant because
(a) green plants can synthesize food.
(b) they can eat everything.
(c) food is stored at one place.
(d) none of the above.

Question. Energy storage at consumer level is called
(a) gross primary productivity
(b) secondary productivity
(c) net primary productivity
(d) net productivity