CBSE Class 12 Biology Ecosystem MCQs Set 02

Question. A scorpion stalks, kills, and then eats a spider. Based on its behavior, which ecological terms describe the scorpion?
(a) producer, herbivore, decomposer
(b) producer, carnivore, heterotroph
(c) predator, carnivore, consumer
(d) predator, autotroph, herbivore

Answer : C

Question. Which one of the following is a characteristic feature of cropland ecosystem?
(a) Absence of weeds
(b) Ecological succession
(c) Absence of soil organisms
(d) Least genetic diversity

Answer : D

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

Answer : B

Question. When man eats fish which feeds on zooplanktons which have eaten small plants, the producer in this chain is
(a) small plants
(b) fish
(c) man
(d) zooplankton.

Answer : A

Question. Secondary productivity is rate of formation of new organic matter by
(a) consumers
(b) decomposers
(c) producers
(d) parasites

Answer : A

Question. Most of the desert plants bloom during night time because
(a) their blooming is controlled by low temperature.
(b) they are sensitive to the phases of moon.
(c) the desert insects eat away flowers during day time.
(d) the desert insects are active during night time.

Answer : D

Question. Which of the following ecological pyramids is generally inverted?
(a) Pyramid of biomass in a sea
(b) Pyramid of numbers in grassland
(c) Pyramid of energy
(d) Pyramid of biomass in a forest

Answer : A

Question. Which one of the following types of organisms occupy more than one trophic level in a pond ecosystem?
(a) Fish
(b) Zooplankton
(c) Frog
(d) Phytoplankton

Answer : A

Question. In a biotic community, the primary consumers are
(a) detritivores
(b) herbivores
(c) carnivores
(d) omnivores.

Answer : B

Question. Water co-deficient contains:
(a) Large thin walled cells
(b) Large-vacuoles
(c) Membrane
(d) All of these

Answer : C

Question. Which one of the following is not a function of an ecosystem?
(a) Energy flow
(b) Decomposition
(c) Productivity
(d) Stratification

Answer : D

Question. Flora and fauna in lake or ponds is
(a) lentic biota
(b) lotic biota
(c) abiotic biota
(d) field layer

Answer : A

Question. The food chain in which microbes breakdown energy rich compounds synthesized by producers is called
(a) ecosystem
(b) parasitic food chain
(c) detritus level chain
(d) predator food chain

Answer : C

Question. During food chain the maximum energy is stored in :
(a) Producers
(b) Decomposers
(c) Herbivoures
(d) Camivourse

Answer : A

Question. The primary producers of the deep-sea hydrothermal vent ecosystem are
(a) green algae
(b) chemosynthetic bacteria
(c) blue-green algae
(d) coral reefs.

Answer : B

Question. Which one of the following is one of the characteristics of a biological community?
(a) Stratification
(b) Natality
(c) Mortality
(d) Sex-ratio

Answer : A

Question. Natural reservoir of phosphorus is
(a) rock
(b) fossils
(c) sea water
(d) animal bones.

Answer : A

Question. Upper part of sea/aquatic ecosystem contains
(a) plankton
(b) nekton
(c) plankton and nekton
(d) benthos.

Answer : A

Question. About 70% of total global carbon is found in
(a) oceans
(b) forests
(c) grasslands
(d) agroecosystems.

Answer : A

Question. Best soil for plant growth is:
(a) Grit
(b) Sandy
(c) Soily
(d) Clay

Answer : D

Question. The mass of living materials at a trophic level at a particular time is called ____
(a) Standing state
(b) Standing crop
(c) Gross primary productivity
(d) Net primary productivity

Answer : B

Question. The upright pyramid of number is absent in
(a) pond
(b) forest
(c) lake
(d) grassland.

Answer : B

Question. Arrange the following ecosystems in increasing order of mean NPP (Tonnes / ha / year)
(a) Tropical deciduous forest
(b) Temperate coniferous forest
(c) Tropical rain forest
(d) Temperate deciduous forest
(a) B < A < D < C
(b) D < B < A < C
(c) A < C < D < B
(d) B < D < A < C

Answer : D

Question. Best type of pyramid which is always true is:
(a) Pyramid or energy
(b) Pyramid of Biomass
(c) Pyramid of number
(d) Both (a) and (c)

Answer : A

Question. The breakdown of detritus into smaller particles by earthworm is a process called
(a) humification
(b) fragmentation
(c) mineralisation
(d) catabolism.

Answer : B

Question. The function of leghaemoglobin during biological nitrogen fixation in root nodules of legumes is to
(a) convert atmospheric N2 to NH3
(b) convert ammonia to nitrite
(c) transport oxygen for activity of nitrogenase
(d) protect nitrogenase from oxygen

Answer : D

Question. A very efficient converter of solar energy with net productivity of 204 kg/m2 or more is the crop
(a) wheat
(b) sugarcane
(c) rice
(d) bajra.

Answer : B

Question. Energy transfer from one trophic level to other, in a food chain, is
(a) 10%
(b) 20%
(c) 1%
(d) 2%.

Answer : A

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

Answer : B

Question. Which one of the following is not a gaseous biogeochemical cycle in the ecosystem
A. Carbon cycle
B. Oxygen cycle
C. Phosphorus cycle
D. Nitrogen cycle

Answer : C

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

Answer : C

Question. The mass of living material at a trophic level at a particular time is called
(a) net primary productivity
(b) standing crop
(c) gross primary productivity
(d) standing state.

Answer : B

Question. Hibernation of some animals:
(a) Regular
(b) Periodic
(c) Suddenly
(d) Temporary

Answer : A

Question. Pyramid of numbers deals with number of
(a) species in an area
(b) individuals in a community
(c) individuals in a trophic level
(d) subspecies in a community.

Answer : C

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

Answer : D

Question. Both hydrarch and xerarch successions lead to
(a) medium water conditions
(b) xeric conditions
(c) highly dry conditions
(d) excessive wet conditions.

Answer : A

Question. Which of the following is not a producer?
a) Agaricus
b) Nostoc
c) Volvox
d) Spirogyra

Answer : A

Question. The biomass available for consumption by the herbivores and the decomposers is called
(a) net primary productivity
(b) secondary productivity
(c) standing crop
(d) gross primary productivity.

Answer : A

Question. How much of the net primary productivity of a terrestrial ecosystem is eaten and digested by herbivores?
a) 10%
b) 1%
c) 40%
d) 90%

Answer : A

Question: Characteristics of humus are
a) It is highly resistant to microbial action
b) Undergoes decomposition at an extremely slow rate
c) Being colloidal in nature serves as nutrient reservoir
d) All of these
Answer: d

Question: Standing crop means
a) Crop in vertical plants excluding ground runner plants
b) The crop that is going to be grown in next season
c) Mass of living material at a particular time
d) None of these
Answer: c

Question: Primary carnivores are the
a) Primary consumers
b) Secondary consumers
c) Detritivores
d) Producers
Answer: b

Question: Detritus consists of
a) Dead plants remains
b) Dead animals remains
c) Animal faecal matter
d) All of these
Answer: d

Question: Decomposers are
a) Heterotrophs
b) Saprotrophs
c) Both 1 and 2
d) Autotrophs
Answer: c

Question: In terrestrial ecosystem a much larger fraction of energy flows
a) Through grazing food chain
b) Through detritus food chain
c) Is bi-directional
d) None of these
Answer: b

Question: In a food chain consisting of eagle, bird, caterpillars, plants; the energy flow will be from
a) Sun, Plant, Eagle, Bird, Caterpillars
b) Sun, Plant, Bird, Caterpillars, Eagle
c) Sun, Plant, Caterpillars, Bird, Eagle
d) Sun, Plant, Caterpillars, Eagle, Bird
Answer: c

Question: Which organism is known as farmers’ friends?
a) Earthworm
b) Flatworm
c) Roundworm
d) Cow
Answer: a

Question: Correct sequence of action of detritivores is
a) Fragmentation, catabolism, leaching, humification, mineralization
b) Fragmentation, catabolism, humification, leaching, mineralization
c) Fragmentation, leaching, catabolism, humification, mineralization
d) Fragmentation, mineralization, leaching, catabolism, humification
Answer: c

Question: Which gas is responsible for the puffed-up appearance of dough?
a) CO₂
b) O₂
c) SO₂
d) NO₂
Answer: a

Match the following organism with their appropriate trophic level in nature
Column – I                      Column – II
A. Zooplanktons             I. Fourth trophic level
B. Grass                       II. Second trophic level
C. Fishes                      III. First trophic level
D. Lion                         IV. Third trophic level
Options :
(A) A – III, B – IV, C – II, D – I
(B) A – I, B – III, C – IV, D – II
(C) A – II, B – III, C – I, D – IV
(D) A – II, B – III, C – IV, D – I
Answer: d

Question: State the correct sentences
A. Warm environment inhibits decomposition
B. Moist environment favours decomposition
C. Low temperature inhibits decomposition
D. Aerobiosis inhibits decomposition
a) All are true
b) A,B,C are true
c) A,C,D are true
d) None of these
Answer: d

Question: Consumers are mainly
a) Autotrophs
b) Heterotrophs
c) Both 1 and 2
d) None of these
Answer: b

Question: If detritus is rich in lignin and chitin, decomposition rate will be
a) Fast
b) Slow
c) No effect
d) None of these
Answer: b

Question: Detritus is broken down by
a) Secondary consumer
b) Tertiary consumer
c) Herbivores
d) Detritivores
Answer: d

Question: The second trophic level in a lake is
a) Phytoplankton
b) Zooplankton
c) Benthos
d) Fishes
Answer: b

Question: Secondary producers are
a) Herbivores
b) Producers
c) Carnivores
d) None of the above
Answer: b

Question: Which one of the following has the largest population in a food chain?
a) Producers
b) Primary consumers
c) Secondary consumers
d) Decomposers
Answer: a

Question: What is the percentage of photosynthetically active radiation (PAR), in the incident solar radiation?
a) 100%
b) 50%
c) 1–5%
d) 2–10%
Answer: b