Please refer to Class 12 Biology Chapter 14 Ecosystem MCQ Questions with answers below. These multiple-choice questions have been prepared based on the latest NCERT book for Class 12 Biology. Students should refer to MCQ Questions for Class 12 Biology with Answers to score more marks in Grade 12 Biology exams. Students should read the chapter Ecosystem and then attempt the following objective questions.

Class 12 Biology Chapter 14 Ecosystem MCQ Questions

Class 12 Biology Chapter 14 Ecosystem MCQ Questions provided below covers all important topics given in this chapter. These MCQs will help you to properly prepare for exams.

Question. Often in the water bodies subjected to sewage pollution, fishes die because of the-
(a) Foul smell
(b) Pathogens in the sewage
(c) Clogging of their gills by solid particles
(d) Reduction in dissolved oxygen caused by microbial activity.

Question. In aquatic ecosystem—(i)—- is the major conduit for energy flow, as against in the terrestrial ecosystem, a much larger fraction of energy flows through the —–(ii)—- than —–(iii)—-.
(a) (i) GFC, (ii) DFC, (iii) GFC
(b) (i) DFC, (ii) GFC, (iii) DFC
(c) (i) GFC, (ii) GFC, (iii) DFC
(d) (i) DFC, (ii) DFC, (iii) GFC

Question. Select the correct option-

a. Predation	i. Cattle and egret
b. Commensalism	ii. Human and Plasmodium vivex
c. Parasitism	iii. Fungi and bacteria
d. Amensalism	iv. Cat and rat

(a) a-iv, b-i, c-ii, d-iii
(b) a-i, b-ii, c-iii, d-iv
(c) a-iii, b-iv, c-i, d-ii
(d) a-ii, b-iii, c-i, d-iv

Question. Identify the correct sequence of succession in a hydrosere-
(a) Free-floating hydrophytes, Sedges, Phytoplankton, Rooted hydrophytes, Grasses and tree.
(b) Phytoplankton. Rooted submerged hydrophytes, Floating hydrophytes, Reed swamp, Marsh meadow and Trees.
(c) Phytoplankton Sedges, Free-Floating hydrophytes, Reed Rooted hydrophytes, Grasses and Trees.
(d) Phytoplankton, Free-Floating hydrophytes, Rooted hydrophytes, Sedges, Grasses and Trees.

Question. Primary productivity does not depend upon-
(a) Plant species
(b) Environmental factors
(c) Herbivore species
(d) Availability of nutrients.

Question. Ecological niche is-
(a) The sum total of environmental factors or conditions, which determine the existence of organism, population, or community in a particular locality.
(b) An ecological adapted zone and is the address of an organism.
(c) The physical position and functional role of a species within the community.
(d) Formed of all plants and animals living at the bottom of lake.

Question. Ozone present in troposphere promotes-
(a) Oxidation of biochemical
(b) Destruction of chlorenchyma
(c) Both 1 and 2
(d) Growth of plants.

Question. The population interactions in which one organism is widely used in medical science for the action of antibiotics is-
(a) Commensalism
(b) Parasitism
(c) Mutualism
(d) Amensalism

Question. Find the incorrect statements.
(a) Biosphere is a global ecosystem
(b) Transfer of energy in food web is indirections but different part
(c) Ecosystem is structural and not functional unit of nature.
(d) Pond and Lake are aquatic ecosystem.

Question. COP-21 is also known as –
(a) The earth summit
(b) The Paris agreement
(c) The Montreal protocol
(d) The Kyoto protocol

Question. In an ecosystem,
I. Cycling of energy and nutrients is a coupled process.
II. Cycling of energy is an dependent process
III. Movement of energy in unidirectional
IV. Both macro and micro consumers are necessary.
(a) Only I
(b) Only III
(3 I and III both
(d) Only IV

Question. Biological equilibrium in ecosystem is maintained with the help of-
(a) Producers and consumers
(b) Consumers and decomposers
(c) Photosynthesis and transpiration
(d) Photosynthesis and respiration

Question. A scrubber in the of a chemical industrial plant removes.
(a) Particular matter of the size 2.5 micrometer or less.
(b) Gases like Sulphur dioxide
(c) Particular matter of the size 5 micrometer or above.
(d) Gases like ozone and methane.

Question. Which of the following is a useful indicator of eutrophication?
(a) BOD
(b) CFC
(c) DDT
(d) 2,4-D

Question. Which one is not correctly matched?
(a) Productivity – rate of biomass production
(b) Gross primary productivity – Photoautotrophs
(c) Net primary productivity – Available biomass for consumption.
(d) Secondary productivity – formation of new organic matter by producer.

Question. Mycorrhizal association plays an important role in which of the following bio-geochemical cycle?
(a) Carbon cycle
(b) Sulphur cycle
(c) Nitrogen cycle
(d) Phosphorous cycle

Question. Ecotone is-
(a) A polluted area
(b) The bottom of a lake
(c) A zone of developing community
(d) A zone of transition between two communities

Question. The UN Conference of Parties on climate change in the year 2019 was held in-
(a) Spain
(b) Peru
(c) Qatar
(d) Poland

Question. Food chain in which micro-organism breakdown the food formed by primary producers:
(a) Parasitic food chain
(b) Detritus food chain
(c) Consumer food chain
(d) Predator food chain

Question. The productivity of the oceans is approximately ——— the annual net primary productivity of the whole biosphere.
(a) Half
(b) One third
(c) One fifth
(d) One fourth

Question. Friends of the Arcata Marsh organization are associated with which of the following?
(a) Noise control
(b) Integrated waste water treatment
(c) Hiroshima disaster
(d) Terror of Bengal

Question. Which factors is responsible for controlling the rate of decomposition?
(a) Climate factor
(b) Chemical composition of detritus
(c) Both 1 and 2
(d) Nature of detritivores

Question. Which of the following statements is incorrect?
(a) All animals do not depend directly on plants for their food need.
(b) The death of the organism is the beginning of the grazing food chain.
(c) Those animals that depends on the primary carnivores for food are labeled as tertiary consumers.
(d) Primary producers in an aquatic ecosystems are various species like phytoplankton’s, algae, and higher plants.

Question. Consider the following four conditions (i)-(iv) and select the correct pair of them as an adaption to the environment in desert lizards.
The conditions-
I. Burrowing in the soil to escape high temperature.
II. Losing heat rapidly from the body during high temperature .
III. Back in the sun when the temperature is low.
IV. Insulating body due to the thick fatty dermis.
(a) III and IV
(b) I and III
(c) II, III, IV
(d) I and II

Question. Eutrophication is caused by-
(a) Phosphate rocks only
(b) Agricultural fertilizers only
(c) Sewage and phosphate rocks
(d) Sewage and agricultural fertilizers

Question. The Montreal Protocol refers to-
(a) Persistent organic pollutants
(b) Global warming and climate change
(c) Substances that deplete the ozone layer
(d) Biosafety of genetically modified organisms

Question. Find the odd one out with respect to the functions of an ecosystem.
(a) Nutrient cycling
(b) Energy flow
(c) Decomposition
(d) Stratification

Question. In the past 150 years there has been a major new input to the carbon cycle. What is it?
(a) There are more humans releasing large quantities of carbon dioxide as respiration.
(b) Increased animal farming has resulted in greater carbon dioxide releases.
(c) Industri zation has resulted in the burning of fossil fuels such as oil and coal, which releases carbon dioxide into the atmosphere.
(d) Changes in ocean currents have lead to the release of large quantities of carbon dioxide

Question. Which of the following trophic levels would have the largest numbers of individuals?
(a) primary producers
(b) omnivores
(c) primary consumers
(d) opportunistic feeders

Question. Which of the following organisms and trophic levels is mismatched?
(a) algae—producer
(b) phytopJankton—primary consumer
(c) fungi—detritivore
(d) bobcat—secondary consumer

Question. Which of the following biogeochemical cycles is characterized by a major reservoir that is gaseous, and a major inorganic form that can only be utilized by a small group of bacteria and cyanobacteria?
(a) Carbon cycle
(b) Nitrogen cycle
(c) Phosphorus cycle
(d) Sulfur cycle

Question. Biogeochemical cycles are global for elements
(a) that are found in the atmosphere.
(b) that are found mainly in the soil,
(c) such as carbon, nitrogen, and phosphorus.
(d) that are dissolved in water.

Question. On average, how much of the energy assimilated at one trophic level is converted to production at the next trophic level (excluding the conversion of sun-light into chemical energy by plants)?
(a) 5 – 20%
(b) Less than 1 %
(c) 20 – 30%
(d) 30 – 50%

Question. The open ocean and tropical rain forest are the two largest contributors to Earth’s net primary productivity because
(a) both have high rates of net primary productivity.
(b) both cover huge surface areas of the Earth.
(c) nutrients cycle fastest in these two ecosystems.
(d) the ocean covers a huge surface area and the tropical rain forest has a high rate of productivity.

Question. Which of the following biogeochemical cycles has a gaseous phase released by volcanoes and fumaroles?
(a) Carbon cycle
(b) Nitrogen cycle
(c) Phosphorus cycle
(d) Sulfur cycle

Question. Nitrogen is often in short supply in terrestrial ecosystems. Why?
(a) There is very little free nitrogen in the air.
(b) Atmospheric nitrogen is primarily in the stratosphere and does not come into contact with terrestrial ecosystems.
(c) Atmospheric nitrogen cannot be used by most organisms. It needs to be converted to useful forms by bacteria and cyanobacteria.
(d) Nitrogen solubility in water is very low and there-fore atmospheric nitrogen enters cells very slowly.

Question. Which of the following statements regarding the hydrological cycle is false?
(a) Most input to the oceans occurs via runoff from rivers.
(b) More water evaporates from the surface of the oceans than falls as rain over the oceans.
(c) Less water evaporates from the surface of the land than falls as rain over the land.
(d) Water found in sedimentary rock is constantly exchanged with the ocean.

Question. Primary productivity
(a) is equal to the standing crop of an ecosystem.
(b) is greatest in freshwater ecosystems.
(c) is the rate of conversion of light to chemical energy in an ecosystem.
(d) is inverted in some aquatic ecosystems.

Question. Stratification in more common is-
(a) Deciduous forest
(b) Tropical rain forest
(c) Temperature forest
(d) Tropical savannah

Question. Frog that feeds an insect is-
(a) Primary consumer
(b) Secondary consumer
(c) Tertiary consumer
(d) Decomposer

Question. In an ecosystem,
(a) energy is recycled through the trophic structure.
(b) energy is usually captured from sunlight by primary producers, passed to secondary producers in the form of organic compounds, and lost to detritivores in the form of heat.
(c) chemicals are recycled between the biotic and abiotic sectors, whereas energy makes a one-way trip through the food web.
(d) there is a continuous process by which energy is lost as heat, and chemical elements leave the ecosystem through runoff

Question. Which of the following always has a “pyramidal” shape, that is, decreasing values at higher trophic levels?
(a) Pyramids of numbers only
(b) Pyramids of biomass only
(c) Pyramids of energy only
(d) Both pyramids of biomass and pyramids of energy

Question. Chemosynthetic bacteria found around deep-sea vents are examples of
(a) producers.
(b) decomposers.
(c) chemical cycling.
(d) secondary productivity

Question. In succession,_________is a crucial factor.
(a) Time
(b) Direction
(c) Height
(d) Space

Question. A rat feeding on potato tuber is-
(a) Carmirore
(b) Decomposer
(c) Producer
(d) Primary consumer

Question. Most of the world’s carbon is found
(a) as carbon dioxide in the atmosphere.
(b) in living organisms. .
(c) as bicarbonate and carbonate ions dissolved in the oceans.
(d) as carbonate minerals in sedimentary rock.

Question. An inverted pyramid of _______ may occasionally be observed in ________ communities.
(a) energy, grassland
(b) energy, forest
(c) biomass, marine
(d) biomass, grassland

Question. Which of the following is not true of a pyramid of productivity?
(a) Only about 10% of the energy in one trophic level is passed into the next level.
(b) Because of the loss of energy at each trophic level, most food chains are limited to three to five steps.
(c) The pyramid of productivity of some aquatic ecosystems is inverted because of the large zooplankton primaryconsumer level
(d) Eating grain-fed beef is an inefficient means of obtaining the energy trapped by photosynthesis

Question. Which of these processes is incorrectly paired with its description?
(a) nitrification—oxidation of ammonium in the soil to nitrite and nitrate
(b) nitrogen fixation—reduction of atmospheric nitrogen into ammonia
(c) denitrification—removal of nitrogen from organic compounds
(d) ammonification—decomposition of organic compounds into ammonia

Question. The phosphorus cycle differs from the carbon cycle in that
(a) 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. What do primary producers have available to convert into biomass?
(a) 10% of secondary productivity
(b) energy used for respiration
(c) gross primary productivity
(d) net primary productivity

Question. Productivity in terrestrial ecosystems is affected by
(a) temperature.
(b) light intensity,
(c) availability of nutrients and water.
(d) all of the above.

Question. Which of the following changes would not result in an increase in net primary production?
(a) Increased precipitation in an and area
(b) Increased soil fertility
(c) Increased latitude (moving from the equator toward the poles)
(d) Moving down a mountain to warmer temperatures

Question. Deer in a forest ecosystem acts as-
(a) Primary consumer
(b) Secondary consumer
(c) Decomposer
(d) None

Question. Which of the following biogeochemical cycles has a major reservoir in sedimentary rock?
(a) Carbon cycle
(b) Nitrogen cycle
(c) Phosphorus cycle / Sulfur cycle
(d) More than one cycle

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. In an ecosystem, bacteria are considered as-
(a) Microconsumers
(b) Macrocomumers
(c) Primary consumers
(d) Secondary consumers

Question. Which of the following is not an objective of integrated pest management?
(a) To eliminate the use of chemicals in agriculture
(b) To develop pest-resistant strains
(c) To use natural biological control methods
(d) To reduce agriculturally-caused pollution

Question. Water logging occurs in-
(a) Sandy soil
(b) Gravel soil
(c) Loamy soil
(d) Clary soil

Question. The nature’s cleaners are-
(a) Produces
(b) Comuners
(c) Decomposer and scavenger
(d) Symbiorts

Question. Green plants constitute-
(a) 1st Trophic level
(b) 2nd trophic level
(c) 3rd trophic level
(d) 4th trophic level

Question. Which of the following biogeochemical cycles is characterized by a form which is a major greenhouse gas?
(a) Carbon cycle
(b) Nitrogen cycle
(c) Phosphorus cycle
(d) Sulfur cycle

Question. Secondary productivity
(a) is measured by the standing crop.
(b) is the rate of biomass production in consumers,
(c) is greater than primary productivity.
(d) is 10% less than primary productivity.

Question. Grasslands can support greater grazing rates by herbivores than forests because
(a) grasslands receive more sunlight.
(b) the net production of grasslands is greater.
(c) grasslands produce less woody plant tissue.
(d) more of the grassland production is above ground.
(d) Energy used to excite a chlorophyll electron

Question. Which of the following statements about food chains and energy flow through ecosystems is false?
(a) A single organism can feed at severaltrophic levels.
(b) The lower the trophic level at which an organism feeds, the more energy is available.
(c) Detritivores feed at all trophic levels except the producer level.
(d) Food webs include two or more food chains.

Question. Photosynthesis and respiration are central to which cycle?
(a) The nitrogen cycle
(b) The carbon cycle
(c) The phosphorus cycle
(d) The sulfur cycle

Question. Most of Earth’s nitrogen is in
(a) the atmosphere.
(b) the oceans.
(c) fresh water.
(d) soil.

Question. What is true about photolithotrophs ?
(a) Obtain energy from radiations and hydrogen from organic compounds
(b) Obtain energy from radiations and hydrogen from inorganic compounds
(c) Obtain energy from organic compounds
(d) Obtain energy from inorganic compounds

Question. Black soil in due to the presence in it of-
(a) Air
(b) Minerals
(c) More Moisture
(d) Organic matter

Question. A plant in the dark uses 0.02 ml of O₂ per minute. The same plant in sunlight releases 0.14 ml of O2 per minute. A correct estimate of its rate of gross primary production is
(a) 0.02 ml of O per minute,
(b) 0.12 ml of O₂ per minute.
(c) 0.14 ml of O₂ per minute.
(d) 0.16 ml of O₂ per minute.

Question. The gas that is removed from the atmosphere by plants and algae is
(a) nitrogen.
(b) oxygen.
(c) carbon dioxide.
(d) methane.

Question. Carbon cycles relatively rapidly except when it is
(a) dissolved in freshwater ecosystems.
(b) released by respiration.
(c) converted into sugars.
(d) stored in petroleum, coal, or wood.

Question. In light, a plant fixes 0.12ml of CO₂ per hour, however, in the dark the same plant releases 0.04 ml of C02 per hour. What is the estimated net primary production of this plant?
(a) 0.04 ml/hour
(b) 0.08 ml/hour
(c) ,0.12 ml/hour
(d) 0.16 ml/hour

Question. Density and distribution of the plant and animal species vary along-
(a) Stratification
(b) Secession
(c) Gradation
(d) Zanation

Question. Which of the environment is richest in free oxygen?
(a) Salt water
(b) Atmosphere
(c) Warm fresh water
(d) Cold Fresh water

Question. The large carnivores such an lion, tiger, which cannot be preyed upon further are called-
(a) Predator
(b) Organolithotrgoh
(c) Top Coninore
(d) Omnivore

Question. In biogeochemical cycles, elements that cycle fastest
(a) are found in organisms.
(b) are scarce.
(c) have a gaseous phase.
(d) do not become fixed into sediment.

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