14.

ECOSYSTEM

Biology Smart Booklet

Theory + NCERT MCQs + NEET PYQs

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 ECOSYSTEM
Ecosystem:
Ecosystem is a biological community where the living and non-living components
interact with each other and their physical environment. It is the functional unit of
nature and varies greatly in size. Let us have a look at the structure, function and
components of ecosystem.

Structure of Ecosystem:
The structure of ecosystem comprises two different components:

1. Biotic

2. Abiotic

Biotic Components:

Biotic Components are the living components involved in shaping the

ecosystem.

It includes biotic factors such as:

Producers: All green plant in the ecosystem are termed as the producers, as they
produce their own food by making use of solar energy. All living organisms are
dependent on plants for both oxygen and food.

Consumers: They include both primary consumers and secondary consumers. As

animals depend on plants for their food, they are called consumers. Primary
consumers feed directly of Producers for their food and the secondary consumers
feed on the primary consumers for their food. All herbivores animals are an
example of Primary consumers. Carnivores and apex predators make up the
secondary and tertiary consumers.

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 Decomposers: They are the saprophytes which include fungi and bacteria.
Decomposers convert the dead matter into nitrogen and carbon dioxide and
the process is called decomposition.

Energy Flow: Energy flow is the flow of energy along the food chain, through
different trophic levels. Energy is passed from the producers to the decomposers
through various trophic levels.

Abiotic Components:

Abiotic components include inorganic materials like air, water, and soil.

Ecosystem Types:
There are three main types of ecosystem:

Terrestrial Ecosystem:

These are the ecosystem found only on land. The terrestrial ecosystems include:

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1. Forest ecosystem

2. Grassland ecosystem

3. Desert ecosystem

4. Mountain ecosystem

5. Aquatic Ecosystem

The aquatic ecosystem is the ecosystem in the water body. It includes:

Freshwater Ecosystem:

The freshwater ecosystem can be divided into the following categories:

1. Lentic: This includes slow-moving or still water such as lakes, ponds, pools, etc.

2. Lotic: This includes fast-moving water bodies such as rivers and streams.

3. Wetlands: These include the environment where soil is saturated with water for a
certain time period.

Oceanic Ecosystem: The ocean ecosystem is the largest ecosystem. It covers

about 71% of the total earth’s surface. This is also known as the marine ecosystem
and is divided into deep water, shallow water and deep ocean surface. A large
variety of corals, echinoderms, brown algae, cephalopods and dinoflagellates
are found here.

Ecological Pyramids:
An ecological pyramid is the graphical representation of the relationship between
different organisms. Each bar of the pyramid represents a different trophic level.

The different types of ecological pyramids include:

Pyramid of Numbers: This represents the number of organisms in each trophic level,
irrespective of their size.

Pyramid of Biomass: This represents the total mass of organisms at each trophic
level.

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 An energy pyramid: An energy pyramid (sometimes called a trophic pyramid or
an ecological pyramid) is a graphical representation, showing the flow of energy
at each trophic level in an ecosystem.

Pyramid of Productivity: It is the total amount of energy present at each trophic

level and the total energy lost between each trophic level.

Ecological Succession: Ecological succession refers to the change in the structure

of species of an ecological community over time. These are of two types:

Primary Succession: This is a type of succession in which plants and animals first
colonize a barren piece of land.

Secondary Succession: This is the type of succession in which an ecosystem that is

destroyed, revives itself.

Function of Ecosystem:
1. The level of organisms regulates the flow of energy.

2. The autotrophs are the producers that produce energy which is transferred
through various trophic levels.

3. The minerals of the biosphere are cycled through the biosphere.

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4. It supports life systems and provides stability.

Decomposition:
It is the process of break down complex organic matter into simpler inorganic
substances such as carbon dioxide, water, and nutrients by the action of
decomposers.

1. Detritus: Dead remains of plants and animals such as leaves, barks, flowers, faecal
matter of animals, etc. constitute detritus.

2. Detritivores: Organisms that feed on detritus are called detritivores. Earthworms,

fungi, etc. are examples of detritivores.

Steps in Decomposition:
1. Fragmentation: It is the breakdown of detritus into smaller particles by the action
of detritivores.

2. Leaching: It's the phenomenon by which water-soluble nutrients sink to the soil
horizon and precipitate as salts that aren't available.

3. Catabolism: It is the breakdown of detritus into simple inorganic nutrients by the

action of bacterial and fungal enzymes.

4. Humification: It is the formation and continuous deposition of a dark-coloured

organic amorphous substance called humus. Humus is extremely resistant to
microbial action and decomposes at a very slow rate. Because it is colloidal, it
acts as a nutrient reservoir.

5. Mineralization: It is the process by which some microorganisms further break down

humus to form simple inorganic nutrients.

Ecological Succession:
Ecological succession is the process of change in the structure of species that
belongs to an ecological community over time. After a mass extinction, the time
scale can be decades or even millions of years. This change occurs orderly and
sequential, parallel with the changes in the physical environment.

1. Pioneer Species: The species that invade a bare area are called pioneer species.

2. Pioneer Community: The community that is capable to invade a bare area is

known as the pioneer community.

3. Climax Community: A community that is almost near to equilibrium with the

environment is called the climax community.

4. Sere: A sequence of ecological communities arising in an area from the initial

pioneer community to the final climax community.

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5. Primary Succession: Primary succession is a type of biological and ecological
succession of plant life. It occurs in an environment in which a new substrate is
deposited. This new substrate is not having any kind of vegetation and other
organisms. It also usually lacks soil and organic matter. It occurs in places such as
land after a lava flow or area left from the retreated glacier.

6. Secondary Succession: Secondary succession is a type of biological and

ecological succession of plant life which takes place in a habitat that has been
previously populated but has since been disturbed or damaged. For instance,
regions where existing vegetation has been removed (due to tree-felling in a
woodland or destructive events such as fires).

Succession of Plants:
Hydrarch: A succession that begins in a water body or aquatic environment is
called Hydrosere or Hydrarch Succession.

Xerarch: Xerosere is a succession of plants that are limited in the availability of

water availability. It includes the different stages in xerarch succession. Xerosere
originates in extremely dry situations such as sand deserts, dunes, salt deserts, rock
deserts, etc.

In secondary succession, the invasion of species depends on the availability of

water, conditions of the soil, and the environment. It also depends on whether any
seeds or other propagules are present. Because soil is already existent, the pace
of succession is substantially faster, and the climax community is reached much
sooner.

Succession always proceeds towards the mesic community.

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Nutrient Cycling:

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 The movement of nutrients through the various components that belong to an
ecosystem is called nutrient cycling. It is also called biogeochemical cycles (bio:
living organism, geo: rocks, air, and water).

Types of Nutrient Cycles:

1. Gaseous.

2. Sedimentary.

Standing State: The total amount of various nutrients like nitrogen, carbon,
phosphorus, calcium, etc., present in the soil at any given time, is referred to as the
standing state. It differs in different kinds of ecosystems and also on the basis of
season.

The atmosphere serves as a reservoir for gaseous nutrient cycles (carbon and
nitrogen).

The reservoir for the sedimentary nutrient cycle (sulfur, phosphorus, etc.) exists in
the earth’s crust.

The rate of release of nutrients into the atmosphere is regulated by environmental

factors.

The reservoir functions to meet with the deficit occurring due to an imbalance
between influx and efflux.

Ecosystem Carbon Cycle:

Carbon is contained by most of the chemicals that make up living tissue. When
the organisms die the carbon contained by them is recycled to be used by future
generations. The movement of carbon through the various components of the
ecosystem is called the carbon cycle.

1. As a result of respiration and combustion, carbon is released into the environment

as CO2.

2. Carbon dioxide is absorbed by producers during the process of photosynthesis to

produce carbohydrates.

3. Animals feed on the producers. The food chain causes carbon to move along
various trophic levels. During breathing, the majority of the carbon eaten is
exhaled as CO2. The animals and plants eventually die.

4. Decomposers eat the dead organisms and break them down. This causes the
carbon in their bodies to be returned to the atmosphere as carbon dioxide. In
some extraordinary conditions, decomposition is blocked. The plant and animal
material may then be turned into fossil fuel for use in the future for combustion.

5. Marine animals may convert some of the carbon in their diet to calcium
carbonate which is then used to make the shells for their bodies. Over time these

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 shells of dead organisms get collected on the seabed and form or converted into
limestone. Due to various activities and movements of the earth, this limestone
may eventually become exposed to the air where it is subjected to weathering.
This results in the back release of carbon into the atmosphere as carbon dioxide.
Carbon dioxide is also released through volcanic action.

6. Human activities have significantly influenced the carbon cycle. Rapid

deforestation and massive burning of fossil fuels have increased the rate of release
of carbon dioxide into the atmosphere.

Phosphorus Cycle:
The phosphorus cycle is the process by which phosphorus moves through the
different layers of the atmosphere that is the lithosphere, hydrosphere, and
biosphere.

Steps in Phosphorus Cycle:

1. Weathering: Weathering of uplifted rocks adds phosphates to the land.

Eventually, some phosphates reach the ocean again.

2. Fertilizers: Phosphate fertilizers from fields might run off straight into the
streams. These may later become part of a soil pool or can be absorbed
by the plants.

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 3. Excretion and Decomposition: Animal excretion (on land or in the ocean)
and animal and plant decomposition both produce phosphates on land
and in water.

4. Dissolved Phosphates: Dissolved phosphates plays important role in forming

ocean sediments by precipitation. The process of conversion of these
sediments into phosphate rocks is a very slow and gradual process.

5. Geological Uplift: Geologic forces can lift up the phosphate rocks very
slowly from the ocean floor or the rocks thick with phosphate in them to
form the huge mountains.

Ecosystem Services:
The results or outcome of ecosystem processes is called ecosystem services.

Services of Healthy Forest Ecosystems:

Purification of air and water.

Mitigation of droughts and floods.

1. Cycling of nutrients.

2. Generation of fertile soils.

3. Providing habitats to wildlife.

4. Maintenance of biodiversity.

5. Pollination of crops.

6. To provide storage site for carbon.

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7. Providing aesthetic, cultural, and spiritual values.

8. The average price tag of these ecosystem services is estimated to be US $ 33

trillion annually.

9. This is near twice the value of the global gross national product GNP (the US $ 18
trillion).

The Calculation, Out of the Total Cost of Various Ecosystem Services:

1. Soil formation accounts for about 50% of the ecosystem services.

2. Recreation for about 10% of these services.

3. Nutrient cycling about 10% of them.

The cost of climate regulation and habitat dark approximate 6% each.

NCERT LINE BY LINE QUESTIONS

14.1 Ecosystem: Structure and Function

1. Vertical distribution of different species occupying different levels is called as
A) Standing crop B) Standing state C) Stratification D) Decomposition
Page-242, Easy
2. Identification and enumeration of plant and animal species of an ecosystem gives its
A) Productivity B) Species composition
C) Physical structure D) Vertical distribution
Page-242, Easy
3. Which one of the following is odd one out from others
A) Decomposition B) Energy flow C) Nutrient cycling D) None
Page-242, Easy
4. The autotrophic components include
A) Phytoplankton B) Some algae C) Marginal plants D) All of these
Page-242, Easy

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5. The decomposers is/are the
A) Fungi B) Bacteria C) Flagellates D) All of these
Page-242, Easy
6. The consumers is/are
A) Zooplankton B) Phytoplanktons C) Marginal plants D) All of these
Page-242, Easy
14.2 Productivity
7. What is the basic requirement for any ecosystem to function and sustain.
A) Primary production B) Decomposers
C) Constant input of solar energy D) Nutrient cycling
Page-242, Easy
8. ________ is defined as the amount of biomass or organic matter produced per unit area over a time period by
plants during photosynthesis
A) Gross primary productivity B) Primary production
C) Secondary production D) None of these
Page-242, Easy
9. Primary production is expressed as-

A) K 𝐶𝑎𝑙𝑚2 B) K 𝐶𝑎𝑙/𝑚2 C) 𝑔/𝑚2 D) both B & C

Page-243, Easy
10. ______ of an ecosystem is the rate of production of organic matter during photosynthesis
A) Net primary productivity B) Secondary production
C) Gross primary productivity D) None of these
Page-243, Easy
11. Net primary productivity (NPP) equals to
A) NPP = R – GPP B) GPP – R = NPP C) NPP = GPP + R D) GPP = R – NPP
Page-243, Easy
12. The rate of formation of new organic matter by consumers is called as
A) primary productivity B) Gross primary productivity
C) Secondary productivity D) Respiratory loss
Page-243, Easy
13. Primary productivity depends on
A) Variety of environmental factors B) Availability of nutrients
C) Photosynthetic capacity of plant D) All of these

Page-243, Easy
14. The annual net primary productivity of the whole biosphere is approximately

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 A) 190 million tons B) 170 million tons C) 170 billion tons D) None of these
Page-243, Easy
14.3 Decomposition
15. Which one of the following is called as “farmer’s friend”?
A) Cow B) Bacteria C) Earthworm D) Crops
Page-243, Easy
16. Who breaks down complex organic matter into inorganic substances like CO2, water etc.
A) Crop roots B) Decomposers C) Grazing Cattle D) None of these
Page-243, Easy
17. The process of breaks down complex organic matter into inorganic substances is called as
A) Fragmentation B) Humification C) Decomposition D) Leaching
Page-243, Easy
18. Detritus is/are
A) Dead plant B) Dead animals C) Fecal matter D) All of these
Page-243, Easy
19. The correct way of decomposition
A) Fragmentation → leaching → humification → catabolism → mineralization
B) Fragmentation → leaching → catabolism → humification → mineralization
C) Fragmentation → catabolism → leaching → mineralization → humification
D) Fragmentation → mineralization → catabolism → leaching → humification
Page-243-244, Medium
20. _________ break down detritus into smaller particles

A) Earthworm B) Detritivores C) Phytoplanktons D) Both A & B are correct

Page-243, Easy
21. Bacteria and fungal enzymes degrade detritus into simpler inorganic substances. This process is called as
A) Leaching B) Fragmentation C) Catabolism D) Humification
Page-243, Easy
22. Humification leads to accumulation of a dark coloured amorphous substance called _______
A) Pectin B) Humus C) Lignin D) None of these
Page-244, Easy
23. Decomposition rate is slower if
A) Detritus rich in lignin & chitin B) Rich in nitrogen & sugars
C) Low in nitrogen & chitin D) Low in lignin
Page-244, Easy

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24. ________ favours decompositions
A) Warm & dry environment B) Warm & moist environment
C) cold & dry environment D) cold & moist environment
Page-244, Easy
14.4 Energy flow
25. PAR stands for
A) Percent active radiation B) Photosynthetically active radiation
C) Power angel regulation D) None of these
Page-245, Easy
26. Plant capture only ______ of the PAR and this amount of energy sustains the entire living world
A) 50 – 60 % B) 40 – 80 % C) 2 – 10 % D) 20 – 40 %
Page-245, Easy
27. The green plant in the ecosystem are called

A) Primary consumer B) Producer

C) Secondary consumer D) None of these
Page-245, Easy
28. Producers in an aquatic ecosystem
A) Phytoplankton B) Algae C) Zooplanktons D) Both A & B
Page-245, Easy
29. Generally, primary consumers will be
A) Carnivores B) Producers C) Herbivores D) All of these
Page-245, Easy
30. In ecosystem, GFC stands for
A) Generic flow control B) Global fund for children
C) Grazing food chain D) None of these
Page-245, Easy
31. Decomposers are also known as
A) Autotrophs B) Standing crops C) Saprotrophs D) None of these
Page-245, Easy
32. Based on the source of their nutrition or food, organisms occupy a specific place in the food chain that is known
as their
A) Food web B) Trophic level C) Niche D) Eco level
Page-245, Easy
33. Match the following

Column I Column II

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 i Plants a Lion

ii Carnivores b Phytoplanktons

iii Herbivores c Wolf

iv Top Carnivores d Cow

35. The standing crop is measured as the

A) Mass of living organisms B) Biomass
C) The no. in a unit area D) All of these
Page-247, Easy
36. Choose the correct sequence –
A) Producer → herbivore → primary carnivore → secondary carnivore
B) Producer → primary carnivore →herbivore → secondary carnivore
C) Primary carnivore → secondary carnivore → herbivore → Producer
D) None of these
Page-247, Easy
14.5 Ecological Pyramids
37. Ecological pyramids are
A) Pyramid of number B) Pyramid of energy
C) Pyramid of biomass D) All of these
Page-247-249, Easy
38. The pyramid of biomass in sea is
A) Always upright B) Generally inverted
C) Both A & B D) None of these
Page-249, Easy
39. Pyramid of energy is
A) Always inverted B) Sometime upright C) Always upright D) Sometimes inverted
Page-249, Easy
40. Identify the pyramid

A) Pyramid of number B) Pyramid of biomass

C) Pyramid of energy D) None of these

Page-248, Easy

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41. Identify the pyramid

A) Pyramid of number B) Pyramid of biomass

C) Pyramid of energy D) None of these
Page-249, Easy
42. Identify the pyramid

A) Pyramid of number B) Pyramid of biomass

C) Pyramid of energy D) None of these

Page-248, Easy
14.6 Ecological succession
43. A community that is in near equilibrium with the environment is called as
A) Pioneer community B) Middle community
C) Climax community D) Sere
Page-250, Easy
44. The gradual and fairly predictable change in the species composition of a given area is called
A) Hydrarch succession B) Ecological succession
C) Pioneer succession D) None of these

Page-250, Easy
45. The entire sequence of communities that successively change in a given area are called
A) Ecosystem B) Pioneer C) Sere D) All of these
Page-250, Easy
46. Areas where primary succession occurs
A) Bare rock B) Newly cold lava
C) Newly created pond D) All of these
Page-250, Easy

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47. Secondary succession begins in areas where
A) No living organism are there
B) Lost all the living organism
C) Natural biotic communities have been destroyed
D) Both B & C
Page-251, Easy
48. Areas where secondary succession occurs
A) Burned and cut forests areas B) Land that have been flooded
C) Abandoned farm lands D) All are correct
Page-251, Easy
49. Select the correct statement
A) secondary succession is faster than primary succession
B) primary succession is faster
C) Both are a equal speed
D) None of these
Page-251, Easy
50. The individual transitional communities are termed as
A) Seral stages B) Pioneer C) Seral communities D) Both A & C are correct
Page-250, Easy
14.6.1 Succession of plants
51. Which type of succession takes place in wet areas
A) Hydrarch succession B) Xerarch succession
C) Mesarch succession D) None of these
Page-251, Easy
52. Xerarch succession occurs in
A) Wet areas B) Cold areas C) Dry areas D) All of these
Page-251, Easy
53. The species that invade a bare area called
A) Sere B) Pioneer species C) Climax species D) None of these
Page-251, Easy
54. In hydrarch succession the successional series progress from
A) Mesic to hydric condition B) Hydric to mesic condition
C) Hydric to xeric condition D) Xeric to mesic condition
Page-251, Easy

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55. In xerarch succession, the succession series progress from
A) Xeric to hydric condition B) Xeric to mesic condition
C) Mesic to xeric condition D) None of these
Page-251, Easy
56. Which one of the following occur as a pioneer species on rocks
A) Bryophytes B) Phytoplankton C) Lichens D) Blue algae
Page-251, Easy
57. Choose the correct sequence of succession in water
A) Phytoplanktons → rooted-submerged plants → rooted floating angiosperms → free floating plants → reed
swamp → marsh-meadow → scrub → the trees → forest
B) Phytoplanktons → free floating plants → rooted-submerged plants → rooted floating angiosperms → reed
swamp → scrub → marsh-meadow → the trees → forest

C) Phytoplanktons → rooted-submerged plants → reed swamp → rooted floating angiosperms → free

floating plants → marsh-meadow → scrub → the trees → forest
D) None of these
Page-251, Easy
58. Choose the correct statement-
A) All succession whether taking place in water or on land, proceeds to a different climax community
B) All succession whether taking place in water or on land, proceeds to a similar climax community the mesic
C) All succession whether taking place in water or on land, proceeds to a similar climax community the xeric
D) All of these
Page-251, Easy
59. Which one of the following is not the part of hydrarch succession
A) Scrub stage B) Tree C) Zooplankton D) Submerged plant stage
Page-251, Easy
60. During succession some species colonise an area and their population become more numerous whereas
population of other species
A) Increases B) Decline and even disappear
C) Migrate D) None of these
Page-251, Easy
61. Why does secondary succession is faster?
A) Because soil is already there B) They have special power
C) Growth of plants is faster D) All of these
Page-251, Easy
62. The climax community remains _______ as long as the environment remains _______.
A) Unstable, unchanged B) Stable, unchanged

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 C) Stable, changed D) Stable, changed
Page-251, Easy
63. The word (term) use for medium water conditions
A) Xeric B) Hydric C) Mesic D) None of these

Page-251, Easy
64. Choose the correct sequence
i) lichens
ii) Grasses
iii) Bryophytes
iv) Higher plants
v) Forest
A) i → ii → iii → iv → B) i → iii → ii → iv → v
C) i → iv → ii → iii → v D) v → iv → i → ii → iii
Page-251, Easy
65. in hydrarch succession, after climax with time the water body is converted into
A) River B) Ocean C) Land D) None of these
Page-251, Easy
66. In hydrarch succession, the pioneer and climax community are respectively
A) Forest, Phytoplanktons B) Phytoplanktons, Forest
C) Mess, Trees D) Lichen, Trees
Page-251, Easy
14.7 Nutrient Cycling
67. The amount of nutrients such as carbon, nitrogen, phosphorus, calcium etc present in the soil at any given time is
referred to as the
A) Nutrients cycle B) Standing crop C) Standing state D) None of these
Page-253, Easy
68. Standing state varies in
A) Different kinds of ecosystem B) On a season basis
C) Different kinds of nutrients D) Both A & B
Page-253, Easy
69. The movement of nutrients elements through the various components of an ecosystem can be called
A) Gaseous cycle B) Nutrient cycling C) Sedimentary cycle D) All of these
Page-253, Easy
70. Another name of nutrient cycling is
A) Gaseous cycle B) Biological cycle

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 C) Biogeochemical cycle D) Biophysical
Page-253, Easy
71. Reservoir for gaseous type of nutrient cycle
A) Earth’s crust B) Rock C) The atmosphere D) Water bodies
Page-253, Easy
72. Reservoir for sedimentary type of Nutrient cycle
A) Ocean B) Earth's crust C) Rock D) Atmosphere
Page-253, Easy
73. Environmental factor to regulate the rate of release of nutrients into the atmosphere.
A) Soil B) Moisture C) Temperature & pH D) All of the above
Page-253, Easy
74. Reason behind nutrients never lost from ecosystem.
A) Because nutrients present in large amount
B) Because they are recycled
C) Because they have no use
D) All of the above
Page-253, Easy
14.7.1 Ecosystem-Carbon Cycle
75. Percent of carbon constitutes in dry weight of organism
A) 60% B) 39% C) 49% D) 71%
Page-254, Easy
76. Which is the first & second most abundant constituent of an organism?
A) Water, phosphorus B) Water, carbon C) Carbon, water D) Carbon, phosphorus
Page-254, Easy
77. How much of total quantity of global carbon is dissolved in the oceans?
A) 88% B) 75% C) 81% D) 71%
Page-254, Easy
78. Carbon cycling occurs through
A) Atmosphere B) Living & dead organism
C) Ocean D) All of the above
Page-254, Easy
79. How much at carbon in fixed annually in the biosphere through photosynthesis?
A) 8 × 1012 kg B) 4 × 1012 kg C) 4 × 1013 kg D) 4.9 × 10 kg
Page-254, Easy

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80. Additional sources for releasing CO2 in the atmosphere is/are-
A) Burning of wood B) Forest fire C) Fossil fuel D) All of the above
Page-254, Easy
81. Human activities have significantly increased the rate of released of CO2 into the atmosphere by
A) Rapid deforestation B) Massive burning of fossil
C) Both A and B D) None of the above

Page-254, Easy
14.7.2 Ecosystem-Phosphorus Cycle
82. Phosphorus is a major constituent of
A) Biological membranes B) Nucleic acids
C) Cellular energy transfer unit D) All of the above
Page-254, Easy
83. Rock is the natural reservoir of
A) Carbon B) Nitrogen C) Phosphorus D) None at these
Page-254, Easy
84. Herbivores & other animals obtain Phosphorus from
A) Rock B) Plants C) Ocean D) Lake

Page-254, Easy
85. The waste products and the dead organism are decomposed by ________ releasing phosphorus.
A) Fungi B) Phosphate-solubilising bacteria
C) Phosphate-unsolubising bacteria D) None of the above
Page-254, Easy
86. Choose the correct statement.
A) Atmospheric inputs of phosphorus through rainfall are much smaller than carbon inputs.
B) Atmospheric inputs of phosphorus through rainfall are larger than carbon inputs.
C) Atmospheric inputs of phosphorus through rainfall are equal to the carbon inputs.
D) None of the above
Page-254, Easy
87. Choose the more correct statement.
A) Gaseous exchange at phosphorus b/w organism & environment are very high.
B) Gaseous exchange of phosphorus b/w organism & environment are low.
C) Gaseous exchange at phosphorus b/w organism & environment are negligible.
D) None at these
Page-254, Easy
88. In natural resevoirs, phosphorus present in the form of

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 A) Phosphite B) Pyrophosphate
C) Phosphates D) None of the above
Page-254, Easy
89. Identify the blanks

A) Detritus Weathering Soil Solution Litter fall

Litter fall Weathering Detritus Soil solution

B)

C) Weathering Litter fall Soil solution Detritus

D) Detritus Soil solution Litter fall Weathering

Page-254, Medium
90. Which one of the following is not a Gaseous nutrient cycle?
A) Oxygen cycle B) Nitrogen cycle C) Sulphur cycle D) None of the above
Page-254, Easy
91. Animals need large quantities of phosphorus to make
A) Shells B) Teeth C) Bones D) All of the above
Page-254, Easy
14.8 Ecosystem Services
92. The products of ecosystem processes are named as
A) Environmental services B) Ecosystem goods
C) Ecosystem services D) All of the above
Page-255, Easy
93. Healthy ecosystems are the base for a
A) Wide range of economic B) Environmental
C) Aesthetic goods & services D) All of the above
Page-255, Easy
94. Examples of Ecosystem services
A) Healthy forest ecosystem purify air & water

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 B) Generate fertile soil
C) Provide storage site for carbon
D) All of the above
Page-255, Easy
95. ________ & his colleagues have very recently tried to put price tags on nature's life-support services.
A) Robert frost B) Robert Constanza C) Robert hook D) Robert Clive
Page-255, Easy
96. Researchers have put an average price tag of ________ a year on fundamental ecosystem services.
A) US $ 33 billion B) US $ 44 billion C) US $ 44 trillion D) US $ 33 trillion
Page-255, Easy
97. GNP stands for
A) Grand national product B) Gross national product
C) Gross national produce D) None of these
Page-255, Easy
98. Out of the total cost at various ecosystem services the soil formation accounts for about.
A) 40% B) 60% C) 50% D) 30%
Page-255, Easy
99. The cost of climate regulation & habitat for wildlife are
A) 8% each B) 6% at overall C) 6% each D) None at the above
Page-255, Easy
100. The value of the global GNP
A) US $ 28 trillion B) US $ 18 Billion C) US $ 33 trillion D) US $ 18 trillion
Page-255, Easy
101. Choose the correct statement.
A) Value of Ecosystem services at biodiversity is difficult to determine.
B) Value of Ecosystem services of biodiversity is very easy to determine.
C) No need to determine the value of Ecosystem services.
D) None of these

Page-255, Easy

NEET PREVIOUS YEARS QUESTIONS

1. What type of ecological pyramid would be obtained with the following data? [2018]
Secondary consumer : 120 g
Primary consumer : 60 g

25
 Primary producer : 10 g
(a) Inverted pyramid of biomass (b) Pyramid of energy
(c) Upright pyramid of biomass (d) Upright pyramid of numbers
2. Which ecosystem has the maximum biomass? [2017]
(a) Grassland ecosystem (b) Pond ecosystem (c) Lake ecosystem (d) Forest ecosystem
3. The term ecosystem was coined by : [2016]
(a) E.P. Odum (b) A.G. Tansley (c) E. Haeckel (d) E. Warming
4. Which of the following is a characteristic feature of cropland ecosystem? [2016]
(a) Absence of soil organisms (b) Least genetic diversity
(c) Absence of weeds (d) Ecological succession
5. Which of the following would appear as the pioneer organisms on bare rocks? [2016]
(a) Lichens (b) Liverworts (c) Mosses (d) Green algae
6. Most animals that live in deep oceanic waters are : [2015]
(a) secondary consumers (b) tertiary consumers (c) detritivores (d) primary consumers
7. Vertical distribution of different species occupying different levels in a biotic community is known as :
[2015]
(a) stratification (b) zonation (c) pyramid (d) divergence
8. The mass of living material at a trophic level at a particular time is called ___________. [2015]
(a) Standing state (b) Net primary productivity
(c) Standing crop (d) Gross primary productivity
9. In an ecosystem the rate of production of organic matter during photosynthesis is termed as : [2015]
(a) Gross primary productivity (b) Secondary productivity
(c) Net productivity (d) Net primary productivity
10. During ecological succession : [2015]
(a) the establishment of a new biotic community is very fast in its primary phase.
(b) the numbers and types of animals remain constant.
(c) the changes lead to a community that is in near equilibrium with the environment and is called pioneer
community.
(d) the gradual and predictable change in species composition occurs in a given area.
11. An association of individuals of different species living in the same habitat and having functional
interactions is : [2015]
(a) Biotic community (b) Ecosystem (c) Population (d) Ecological niche
12. Secondary succession takes place on/in : [2015]
(a) degraded forest (b) newly created pond (c) newly cooled lava (d) bare rock

13. Most animals that live in deep oceanic waters are : [2015]
(a) tertiary consumers (b) secondary consumers
(c) detritivores (d) primary consumers
14. Increase in concentration of the toxicant at successive trophic levels is known as ___________. [2015]
(a) Biodeterioration (b) Biotransformation (c) Biogeochemical (d) Biomagnification
15. In which of the following, both pairs have correct combination? [2015]
(a) Gaseous nutrient cycle Carbon and Sulphur Sedimentary nutrient cycle Nitrogen and Phosphorus
(b) Gaseous nutrient cycle Nitrogen and Sulphur Sedimentary nutrient cycle Carbon and Phosphorus
(c) Gaseous nutrient cycle Sulphur and Sedimentary nutrient cycle Phosphorus Carbon and Nitrogen
(d) Gaseous nutrient cycle Carbon and Nitrogen Sedimentary nutrient cycle Sulphur and Phosphorus
16. Match the following and select the correct option [2014]
Column I Column II
A. Earthworm I. Pioneer species
B. Succession II. Detritivore
C. Ecosystem service III. Natality
D. Population growth IV. Pollination
(a) A – I; B – II; C – III; D – IV (b) A – IV; B – I; C – III; D – II

26
 (c) A – III; B – II; C – IV; D – I (d) A – II, B – I; C – IV; D – III
17. If 20 J of energy is trapped at producer level, then how much energy will be available to peacock as food
in the following chain? [2014]
plant mice snake peacock
(a) 0.02 J (b) 0.002 J (c) 0.2 J (d) 0.0002 J
18. Given below is a simplified model of phosphorus cycling in a terrestrial ecosystem with four blanks (A-
D). Identify the blanks [2014]

19. Which of the following ecological pyramids is generally inverted? (NEET-2019)

(1) Pyramid of numbers in grassland (2) Pyramid of energy
(3) Pyramid of biomass in a forest (4) Pyramid of biomass in a sea
20. Which of the following statements is incorrect? (NEET-2020 COVID19)
(1) Biomass decreases from first to fourth trophic level
(2) Energy content gradually increases from first to fourth trophic level
(3) Number of individuals decreases from first trophic level to fourth trophic level
(4) Energy content gradually decreases from first to fourth trophic level

21. Which of the following statements is incorrect regarding the phosphorus cycle? (NEET-2020 COVID19)
(1) Phosphates are the major form of phosphorus reservoir
(2) Phosphorus solubilising bacteria facilitate the release of phosphorus from organic remains
(3) There is appreciable respiratory release of phosphorus into atmosphere
(4) It is sedimentary cycle
22. The rate of decomposition is faster in the ecosystem due to following factors EXCEPT:-
(NEET-2020 COVID19)
(1) Detritus rich in sugars (2) Warm and moist environment
(3) Presence of aerobic soil microbes (4) Detritus richer in lignin and chitin
23. Which of the following ecological pyramids is generally inverted? (NEET-2020 COVID19)
(1) Pyramid of numbers in grassland (2) Pyramid of energy
(3) Pyramid of biomass in a forest (4) Pyramid of biomass in a sea
24. In relation to Gross primary productivity and Net primary productivity of an ecosystem, which one of
the following statements is correct? (NEET-2020)

27
 1) There is no relationship between Gross primary productivity and Net primary productivity
2) Gross primary productivity is always less than net primary productivity
3) Gross primary productivity is always more than net primary productivity
4) Gross primary productivity and Net primary productivity are one and same
25. Mach the trophic levels with their correct species examples in grassland ecosystem (NEET-2020)
(a) Fourth trophic level (i) Crow
(b) Second trophic level (ii) Vulture
(c) First trophic level (iii) Rabbit
(d) Third trophic level (iv) Grass
Select the correct option
(a) (b) (c) (d)
1) (i) (ii) (iii) (iv)
2) (ii) (iii) (iv) (i)
3) (iii) (ii) (i) (iv)
4) (iv) (iii) (ii) (i)
26. Which of the following statements is incorrect? (NEET-2020)
(1) Biomass decreases from first to fourth trophic level
(2) Energy content gradually increases from first to fourth trophic level
(3) Number of individuals decreases from first trophic level to fourth trophic level
(4) Energy content gradually decreases from first to fourth trophic level
27. Which of the following statements is incorrect regarding the phosphorus cycle? (NEET-2020)
(1) Phosphates are the major form of phosphorus reservoir
(2) Phosphorus solubilising bacteria facilitate the release of phosphorus from organic remains
(3) There is appreciable respiratory release of phosphorus into atmosphere
(4) It is sedimentary cycle
28. The amount of nutrients such as carbon, nitrogen, phosphorus and calcium present in the soil at any given time, is
referred as: [NEET-2021]

1) Climax community 2) Standing state 3) Standing crop 4) Climax

29. In the equation GPP-R=NPP R represents: [NEET-2021]

1) Retardation factor 2) Environment factor 3) Respiration losses 4) Radiant energy

30. Which of the following statement is not correct? [NEET-2021]

1) Pyramid of biomass in sea is generally upright

2) Pyramid of energy is always upright

3) Pyramid of numbers in a grassland ecosystem is up right

4) Pyramid of biomass in sea is generally inverted

31. Given below are two statements. [NEET-2022]

Statement I : Decomposition is a process in which the detritus is degraded into simpler substances by
microbes .
Statement II : Decomposition is faster if the detritus is rich in lignin and chitin
In the light of the above statements, choose the correct answer from the options given below:
1) Both statement I and statement II are correct
2) Both statement I and Statement II are incorrect
3) Statement I is correct but statement II is incorrect
4) Statement I is incorrect but statement II is correct
32. Which one of the following will accelerate phosphorus cycle? [NEET-2022]
1) Burning of fossil fuels 2) Volcanic activity
3) Weathering of rocks 4) Rain fall and storms

28
33. Detritivores breakdown detritus into smaller particles. This process is called: [NEET-
2022]
1) Catabolism 2) Fragmentation
3) Humification 4) Decomposition

NCERT LINE BY LINE QUESTIONS – ANSWERS

Q 1 2 3 4 5 6 7 8 9 10

Ans C B D D B A C B D C

Q 11 12 13 14 15 16 17 18 19 20

Ans B C D C C B C D B D

29
 Q 21 22 23 24 25 26 27 28 29 30

Ans B B A B B C B D C C

Q 31 32 33 34 35 36 37 38 39 40

Ans C C A B D A D B C B

Q 41 42 43 44 45 46 47 48 49 50

Ans C A C B C D D D A D

Q 51 52 53 54 55 56 57 58 59 60

Ans A C B B B A A B C B

Q 61 62 63 64 65 66 67 68 69 70

Ans A B B B C B C D D C

Q 71 72 73 74 75 76 77 78 79 80

Ans C B D B C B D D C D

Q 81 82 83 84 85 86 87 88 89 90

Ans C D C B B A C C D C

Q 91 92 93 94 95 96 97 98 99 100

Ans D C D D B D B C C D

Q 101

Ans A

NEET PREVIOUS YEARS QUESTIONS-ANSWERS

1 (a) 2 (d) 3 (b) 4 (b) 5 (a) 6 (c) 7 (a) 8 (c) 9 (a) 10 (d)
11 (a) 12 (a) 13 (c) 14 (d) 15 (d) 16 (d) 17 (a) 18 (c) 19 (4) 20 (2)
21 (3) 22 (4) 23 (4) 24 (3) 25 (2) 26 (2) 27 (3) 28 (2) 29 (3) 30 (1)
31 (3) 32 (3) 33 (2)

NEET PREVIOUS YEARS QUESTIONS-EXPLANATIONS

1. (a) The given data depicts the inverted pyramid of biomass, usually present in aquatic ecosystem. Upright
pyramid of biomass and numbers are not possible, as the data depicts primary producer is less than
primary consumer and this is less than secondary consumers. Pyramid of energy is always upright.
2. (d) Forest ecosystem has the maximum biomass. Some very highly productive ecosystems are :
– Tropical rain forest
– Coral reef
– Estuaries
– Sugarcane fields
3. (b) Sir Arthur George Tansley was an English botanist and a pioneer in the science of ecology who coined
the term ecosystem.
4. (b) Cropland ecosystem is largest anthropogenic ecosystem characterised by less diversity and high
productivity.

30
5. (a)
6. (c) Detritivores are the organisms which feed on dead plants and animal residues.
7. (a)
8. (c) Standing crop is the amount of living biomass in an ecosystem. It indicates the productivity &
luxuriance of growth. It is expressed in the form of number or biomass of organisms per unit area.
9. (a) Gross Primary Productivity (GPP) is the rate of production of biomass or accumulation of energy by
green plants per unit area per unit time. GPP depends on the chlorophyll content.
10. (d) The gradual and predictable change, in the composition of species takes place in a given area during
ecological succession.
11. (a) Biotic community is an association of individuals of different species living in the same habitat and
showing functional interactions.
12. (a) Secondary succession takes place in disturbed area having poor vegetation.
13. (c) Detritivores are the organisms which feed on dead plants and animal residues.
14. (d) Biomagnification means an increase in concentration of toxins through the trophic levels of a food
chain.
15. (d) Carbon and Nitrogen are gaseous nutrient cycle. Sulphur and phosphorus are sedimentary nutrient cycle.
16. (d) Detrivores, (e.g. earthworm) break down detritus into smaller particles. The species that invade a bare
area in succession is called pioneer species. The products of ecosystem processes are termed as
ecosystem services, e.g., healthy forest ecosystems purify air and water, mitigate droughts and floods
etc. Natality refers to number of births during a given period in the population.
17. (a) 18. (c)
24. Gross primary productivity of an ecosystem is the rate of production of new organic matter during
photosynthesis. Net primary productivity is GPP-respiration. So gross primary productivity is always
more than NPP
25. Grassland ecosystem has the following trophic levels
First trophic level– Grass
Second trophic level– Rabbit
Third trophic level– Crow
Fourth trophic level– Vulture
28. Standing sate

29. Gross primary production minus respiration loss of energy is equal to net primary production. So R represents
respiratory loss of energy

30. In an aghatic ecosystem the biomass increases from lower trophic levels to higher trophic levels. So the
pyramid of biomass in a sea ecosystem in inverted
31. Statement I is correct but statement II is incorrect
Lignin & Chitin are complex chemicals decomposition is slow
32 Weathering of rocks will accelerate the ‘P’ cycle
33. In fragmentation breakdown of detritus occurs

31