Class-12 Biology Ch-13 Organisms and Populations MCQs Exam 2027

Topic 1: Organisms and Environment

1. What is the amount of $CO_{2}$ in the atmosphere? [2019A]

(A) 0.03%

(B) 0.3%

(C) 0.003%

(D) 3%

2. Which instrument is used to measure wind speed? [2019A]

(A) Anemometer

(B) Lactometer

(C) Photometer

(D) None of these

3. Which of the following helps in maintaining soil fertility?

(A) Chemical fertilizers

(B) Bio-fertilizers (Organic manure)

(C) Pesticides

(D) None of these

4. Water holding capacity is a property of:

(A) Soil

(B) Plants

(C) Water

(D) Animals

5. In which type of soil is the water-holding capacity highest?

(A) Clay

(B) Sand

(C) Silt

(D) None of these

6. How is the amount of water present in the soil measured?

(A) Hydrometer

(B) Hygrometer

(C) Osmometer

(D) None of these

7. The process of soil formation is called: [2026]

(A) Pedogenesis

(B) Humification

(C) Calcification

(D) None of these

8. The instrument used to measure light intensity is: [2026]

(A) Lux meter

(B) Thermometer

(C) Barometer

(D) Anemometer

9. Organisms that can tolerate a wide range of temperatures are called: [2026]

(A) Stenothermal

(B) Eurythermal

(C) Isothermal

(D) None of these

10. Organisms that are restricted to a narrow range of salinity are: [2026]

(A) Euryhaline

(B) Stenohaline

(C) Halophytes

(D) None of these

Topic 2: Adaptations

11. Which adaptation is essential for animals living in the desert? [2024A]

(A) Hibernation

(B) Aestivation

(C) Excretion of concentrated urine

(D) All of the above

12. Which of the following adaptations is found in aquatic plants? [2024A]

(A) Aerenchyma

(B) Absence of cuticle

(C) Absence of stomata

(D) All of the above

13. Stomata in ‘Zerophytes’ are:

(A) Large

(B) Sunken

(C) Absent

(D) Only on the upper surface

14. Sunken stomata are found in: [2021A]

(A) Hydrophytes

(B) Xerophytes

(C) Mesophytes

(D) Halophytes

15. Plants which are NOT found in aquatic environments are: [2020A]

(A) Hydrilla

(B) Trapa

(C) Nelumbo

(D) Acacia (Babul)

16. Root cap is absent in:

(A) Xerophytes

(B) Mesophytes

(C) Hydrophytes

(D) Halophytes

17. An example of desert adaptation is: [2022A]

(A) Agave

(B) Opuntia (Cactus)

(C) Both (A) and (B)

(D) Trapa

18. In amphibious plants, stomata are found:

(A) On the upper surface

(B) On the lower surface

(C) On both surfaces

(D) Not on any surface

19. Plants that grow in deserts are called: [2018A]

(A) Hydrophytes

(B) Xerophytes

(C) Mesophytes

(D) None of these

20. Which of the following is a Xerophytic plant? [2022A]

(A) Cuscuta

(B) Opuntia

(C) Trapa

(D) None of these

21. Where do Lithophytes grow? [2026]

(A) In water

(B) On rocks

(C) In deserts

(D) In marshes

22. Halophytes are found in: [2026]

(A) Saline water or salty soil

(B) Fresh water

(C) Cold regions

(D) Sand

23. Pneumatophores (Respiratory roots) are found in: [2026]

(A) Maize

(B) Rhizophora (Mangroves)

(C) Cactus

(D) Hydrilla

24. Viviparity is a characteristic of which type of plants? [2026]

(A) Hydrophytes

(B) Halophytes

(C) Mesophytes

(D) Xerophytes

25. In desert plants, photosynthesis is performed by what when leaves are shed? [2026]

(A) Roots

(B) Green stems (Phylloclade)

(C) Flowers

(D) Thorns

26. Mammals from colder climates generally have shorter ears and limbs; this is: [2026]

(A) Bergmann’s Rule

(B) Allen’s Rule

(C) Cope’s Rule

(D) Jordan’s Rule

Topic 3: Population and its Attributes

27. The study of population is called: [2022A, 2016A]

(A) Calligraphy

(B) Psychology

(C) Biography

(D) Demography

28. The number of deaths in a population during a given period is called: [2019A]

(A) Natality

(B) Mortality

(C) Mobility

(D) None of these

29. The geometric representation of age structure is a characteristic of: [2022A]

(A) Biological community

(B) Population

(C) Landscape

(D) Ecosystem

30. Maximum growth rate is found in:

(A) Senescent phase

(B) Lag phase

(C) Exponential (Log) phase

(D) Stationary phase

31. The growth rate of the human population is affected by:

(A) Birth rate

(B) Death rate

(C) Immigration

(D) All of the above

32. Due to which factors does population density decrease?

(A) Birth rate and Emigration

(B) Death rate and Immigration

(C) Death rate and Emigration

(D) Birth rate and Immigration

33. The formula for Exponential growth is:

(A) $\frac{dN}{dt} = rN$

(B) $\frac{dN}{rN} = dt$

(C) $\frac{rn}{dN} = dt$

(D) $\frac{dn}{dt} = rN$

34. A group of individuals of the same species is called:

(A) Community

(B) Population

(C) Species

(D) Ecology

35. What happens due to overpopulation? [2018A]

(A) Decrease in income

(B) Decrease in land

(C) Decrease in minerals

(D) All of these

36. Due to which factors does a population remain ever-changing? [2021A]

(A) Physical

(B) Biological

(C) Both (A) and (B)

(D) None of these

37. The value of biotic potential is calculated by: [2022A]

(A) Subtracting death rate from birth rate

(B) Adding death rate to birth rate

(C) Quotient of birth rate and death rate

(D) None of these

38. Which method is used to measure population density? [2026]

(A) Biomass

(B) Number

(C) Percent cover

(D) All of these

39. In an age pyramid, if the base is broad, it indicates: [2026]

(A) Growing population

(B) Declining population

(C) Stable population

(D) None of these

40. What is the formula for population density? [2026]

(A) $N/W$

(B) $N/S$

(C) $N/V$

(D) $N/A$

41. The inherent capacity of a population to increase at maximum rate is: [2026]

(A) Biotic potential

(B) Carrying capacity

(C) Birth rate

(D) Population growth

42. The shape of a Logistic Growth curve is: [2026]

(A) J-shaped

(B) S-shaped (Sigmoid)

(C) Straight line

(D) Circular

43. When resources are limited, the population growth is: [2026]

(A) Exponential

(B) Logistic

(C) No growth

(D) None of these

44. ‘Natality’ refers to: [2026]

(A) Death rate

(B) Birth rate

(C) Emigration

(D) Population density

45. Carrying Capacity is denoted by which letter? [2026]

(A) N

(B) r

(C) K

(D) t

46. World Population Day is celebrated on: [2026]

(A) June 5

(B) July 11

(C) December 1

(D) April 22

Topic 4: Interactions

47. Mycorrhiza is an example of:

(A) Symbiosis

(B) Ectoparasite

(C) Endoparasite

(D) Decomposer

48. Lichen is an indicator of: [2015A, 2021A]

(A) $CO$ pollution

(B) $SO_{2}$ pollution

(C) $CO_{2}$ pollution

(D) Water pollution

49. Which of the following is an insectivorous plant? [2024A]

(A) Drosera

(B) Nepenthes

(C) Both (A) and (B)

(D) Hydrilla

50. The symbiotic association between fungi and roots of higher plants is: [2021A]

(A) Mycorrhiza

(B) Lichen

(C) Phycobiont

(D) None of these

51. Earthworms and plants show what kind of relationship? [2024A]

(A) Commensalism

(B) Mutualism

(C) Protocooperation

(D) Parasitism

52. An Orchid plant growing on the branch of a Mango tree is an example of: [2023A]

(A) Mutualism

(B) Commensalism

(C) Parasitism

(D) Competition

53. Lichen is a combination of:

(A) Algae and Fungi

(B) Algae and Bryophyta

(C) Fungi and Pteridophyta

(D) None of these

54. Mutual dependence (Mutualism) occurs between: [2022A]

(A) E. coli and Humans

(B) Butterflies and Flowers

(C) Hermit crab and Sea anemone

(D) All of the above

55. Mycorrhiza is an example of: [2021A]

(A) Decomposer

(B) Symbiont

(C) Parasite

(D) Commensal

56. Lichen is an example of: [2026]

(A) Mutualism

(B) Commensalism

(C) Parasitism

(D) Predation

57. The interaction between two different species is called: [2026]

(A) Interspecific interaction

(B) Intraspecific interaction

(C) Competition

(D) Predation

58. Which was used to control the invasive Cactus in Australia? [2026]

(A) Moth

(B) Calotropis

(C) Phytophagous insects

(D) Virus

59. Which of the following is the pollinator of ‘Ophrys’? [2026]

(A) Wasp

(B) Humming bird

(C) A species of bee

(D) Bat

60. Antibiosis is an example of: [2026]

(A) Commensalism

(B) Parasitism

(C) Interspecific opposition

(D) Mutualism

61. In ‘Amensalism’, one species is harmed and the other is: [2026]

(A) Benefited

(B) Harmed

(C) Neither benefited nor harmed

(D) None of these

62. Gause’s Competitive Exclusion Principle states: [2026]

(A) Two species cannot occupy the same niche indefinitely

(B) Superior species eventually eliminates the other

(C) Both (A) and (B)

(D) None of these

63. Brood Parasitism is seen in: [2026]

(A) Crow and Cuckoo

(B) Tiger and Deer

(C) Ant and Aphid

(D) Buffalo and Egret

64. Cuscuta (Amarbel) is an example of: [2026]

(A) Total stem parasite

(B) Partial stem parasite

(C) Commensal

(D) Mutualist

65. What is the relationship between a Tiger and a Deer? [2026]

(A) Mutualism

(B) Predation

(C) Parasitism

(D) Commensalism

Topic 5: Ecosystem – Structure and Function

66. In ecosystem terminology, ‘green plants’ are called: [2017A]

(A) Consumers

(B) Producers

(C) Herbivores

(D) Omnivores

67. A Grasshopper in an ecosystem is a: [2021A]

(A) Producer

(B) Primary consumer

(C) Secondary consumer

(D) Decomposer

68. In an aquatic ecosystem, Trophic Level 1 (T1) consists of:

(A) Phytoplankton

(B) Zooplankton

(C) Small fish

(D) Big fish

69. What is the path of energy flow in an ecosystem? [2022A]

(A) Producer $\rightarrow$ Herbivore $\rightarrow$ Carnivore $\rightarrow$ Decomposer

(B) Producer $\rightarrow$ Carnivore $\rightarrow$ Herbivore $\rightarrow$ Decomposer

(C) Herbivore $\rightarrow$ Producer $\rightarrow$ Carnivore $\rightarrow$ Decomposer

(D) Decomposer $\rightarrow$ Carnivore $\rightarrow$ Herbivore $\rightarrow$ Producer

70. The process occurring in dead animals is called:

(A) Decomposition

(B) Socialization

(C) Accumulation

(D) Activation

71. Herbivorous insects are called:

(A) Primary consumers

(B) Secondary consumers

(C) Tertiary consumers

(D) Top carnivores

72. What is the main source of energy in an ecosystem? [2018A, 2024A]

(A) Sun

(B) Green plants

(C) Air

(D) ATP

73. Energy flow in an ecosystem is: [2024A]

(A) Unidirectional

(B) Bidirectional

(C) Multidirectional

(D) None of these

74. The source of energy in any ecosystem is: [2015A]

(A) Sugar

(B) Sunlight

(C) ATP

(D) Green plants

75. Green plants in an ecosystem are: [2017A]

(A) Producers

(B) Consumers

(C) Decomposers

(D) None of these

76. A grasshopper is: [2021A]

(A) Producer

(B) Primary consumer

(C) Both (A) and (B)

(D) None of these

77. Those who obtain nutrition from dead organic matter are: [2026]

(A) Saprotrophs

(B) Heterotrophs

(C) Detritivores

(D) Parasites

78. The raw material for decomposition is called: [2026]

(A) Humus

(B) Inorganic substance

(C) Detritus

(D) Organic substance

79. Secondary consumers are also called: [2026]

(A) Herbivores

(B) Primary carnivores

(C) Secondary carnivores

(D) Consumers

80. What percentage of PAR is captured by plants? [2026]

(A) 50%

(B) 2-10%

(C) 10%

(D) 20%

81. Energy flow in a food chain is: [2026]

(A) Unidirectional

(B) Bidirectional

(C) Multidirectional

(D) None of these

82. Who gave the 10% Law of energy? [2026]

(A) Odum

(B) Lindeman

(C) Elton

(D) Haeckel

83. Interconnected food chains are called: [2026]

(A) Food Web

(B) Ecological pyramid

(C) Energy flow

(D) Biological succession

84. Decomposers in an ecosystem are: [2026]

(A) Autotrophs

(B) Heterotrophs

(C) Saprophytes

(D) Both (B) and (C)

85. Scavengers in an ecosystem are: [2026]

(A) Vultures and Eagles

(B) Bacteria

(C) Green plants

(D) Lions

86. The trophic level of a Lion in a forest ecosystem is: [2026]

(A) $T_1$

(B) $T_2$

(C) $T_3$

(D) $T_4$

87. An example of an artificial ecosystem is: [2026]

(A) Forest

(B) Lake

(C) Crop field

(D) Ocean

88. Primary productivity depends on: [2026]

(A) Plant species

(B) Availability of light

(C) Nutrients

(D) All of the above

Topic 6: Ecological Pyramids

89. Who first proposed the concept of ecological pyramids?

(A) Charles Elton

(B) Odum

(C) Haeckel

(D) Warming

90. The pyramid of numbers in a grassland ecosystem is: [2026]

(A) Upright

(B) Inverted

(C) Tilted

(D) Linear

91. The pyramid of biomass in a pond ecosystem is: [2026]

(A) Upright

(B) Inverted

(C) Linear

(D) Irregular

92. The pyramid of energy is always: [2026]

(A) Upright

(B) Inverted

(C) Horizontal

(D) Sometimes upright, sometimes inverted

93. Which pyramid can never be inverted? [2026]

(A) Pyramid of numbers

(B) Pyramid of biomass

(C) Pyramid of energy

(D) All of the above

Topic 7: Ecological Succession

94. A climax community is found in: [2019A]

(A) Balanced region

(B) Transition region

(C) Bare land

(D) None of these

95. The nature of a Climax community depends on: [2019A]

(A) Water

(B) Soil

(C) Climate

(D) Temperature

96. Lithosere (Succession on rocks) is: [2022A]

(A) Life-less

(B) Bare rocky region

(C) Both (A) and (B)

(D) Shivalik

97. The sequence of changes in a specific area is called:

(A) Ecological succession

(B) Ecological adaptation

(C) Population explosion

(D) None of these

98. The first species to invade a bare area in succession is: [2026]

(A) Climax species

(B) Pioneer species

(C) Intermediate species

(D) None of these

99. Hydrarch succession starts in: [2026]

(A) Dry area

(B) Aquatic area

(C) Rocks

(D) Deserts

Topic 8: Biogeochemical Cycles and Environment

100. Ozone layer protects us from which radiation? [2017A]

(A) Infrared

(B) Ultraviolet (UV rays)

(C) X-ray

(D) None of these

101. The cycling of minerals in an ecosystem is called: [2026]

(A) Geological cycle

(B) Biogeochemical cycle

(C) Chemical cycle

(D) Biological cycle

102. Which of the following is NOT a gaseous biogeochemical cycle? [2026]

(A) Nitrogen cycle

(B) Carbon cycle

(C) Phosphorus cycle

(D) Oxygen cycle

103. The thickness of Ozone in the stratosphere is measured in: [2026]

(A) Decibels

(B) Dobson Units (DU)

(C) Pascal

(D) Meters

Topic 9: Biodiversity and Conservation

104. Rhino Sanctuary is located in which state? [2020A]

(A) Assam

(B) Bengal

(C) Uttar Pradesh

(D) Bihar

105. An example of Ex-situ conservation is: [2023A]

(A) Sacred groves

(B) National parks

(C) Seed Bank

(D) Wildlife sanctuaries

106. How many ‘mega-biodiversity’ countries are in the world? [2026]

(A) 25

(B) 34

(C) 14

(D) 17

107. Which is called the “Lungs of the earth”? [2026]

(A) Forest

(B) Temperate region

(C) Amazon rainforest

(D) Tropical Savannah

108. Which species became extinct due to over-exploitation? [2026]

(A) Passenger pigeon

(B) Giant Panda

(C) Nile Perch

(D) 200 species of cichlid fish

109. Economic benefits from nature is what kind of argument for biodiversity conservation? [2026]

(A) Narrowly utilitarian

(B) Broadly utilitarian

(C) Ethical

(D) All of these

Topic 10: Misc. Important Concepts

110. Who first used the term ‘Ecology’?

(A) Odum

(B) Reiter

(C) Haeckel

(D) Aristotle

111. An important factor in the formation of new species is: [2021A]

(A) Competition

(B) Mutation

(C) Isolation

(D) Continuous variation

112. The cause of decrease in relative biological balance is:

(A) Low temperature

(B) High temperature

(C) Radiation

(D) Pollution

113. Intraspecific reproductive capacity is:

(A) Birth rate

(B) Carrying capacity

(C) Biodiversity

(D) Reproductive potential

114. Which of the following has the highest number of species?

(A) Birds

(B) Angiosperms

(C) Fungi

(D) Insects

115. Flowers pollinated by wind are called: [2020A]

(A) Entomophilous

(B) Anemophilous

(C) Hydrophilous

(D) None of these

116. Frequent glaciation caused less time for species evolution in which region? [2026]

(A) Temperate region

(B) Tropical region

(C) Polar region

(D) All regions

117. Guttation is: [2026]

(A) Transpiration

(B) Release of water droplets from leaf margins

(C) Diffusion

(D) Osmosis

118. Sarcophagy means: [2026]

(A) Eating fruits

(B) Eating meat

(C) Eating grass

(D) Eating wood

119. ‘Nepenthes’ is: [2026]

(A) Producer

(B) Consumer

(C) Both (A) and (B)

(D) Decomposer

120. Who coined the term ‘Ecological Niche’? [2026]

(A) Grinnell

(B) Odum

(C) Darwin

(D) Lamarck

121. Competition between members of the same population is: [2026]

(A) Intraspecific

(B) Interspecific

(C) Both (A) and (B)

(D) None of these

122. An earthworm is called: [2026]

(A) Friend of farmer

(B) Detritivore

(C) Both (A) and (B)

(D) Producer

123. An example of a Biome is: [2026]

(A) Desert

(B) Rainforest

(C) Tundra

(D) All of these

124. Herbivores are: [2026]

(A) Producers

(B) Primary consumers

(C) Secondary consumers

(D) Decomposers

125. The two main categories of ecosystems are: [2026]

(A) Terrestrial and Aquatic

(B) Natural and Artificial

(C) Both (A) and (B)

(D) None of these

126. What is the result of ‘Emigration’ in a population? [2026]

(A) Increase in number

(B) Decrease in number

(C) No change

(D) None of these

127. Camouflage is present for: [2022A]

(A) Conservation

(B) Hiding

(C) Reproduction

(D) Both (A) and (C)

128. According to the peak of nature (stable ecosystem), growth follows:

(A) J-curve

(B) S-curve

(C) L-curve

(D) All of the above

129. In a food chain, herbivorous insects are: [2026]

(A) Primary consumers

(B) Secondary consumers

(C) Tertiary consumers

(D) Top carnivores

130. Which is NOT a primary consumer of an ecosystem? [2026]

(A) Zooplankton

(B) Cow

(C) Grasshopper

(D) Wolf

131. Phytoplanktons are: [2026]

(A) Aquatic producers

(B) Aquatic consumers

(C) Aquatic decomposers

(D) Desert plants

132. Fungi help plants in Mycorrhiza for: [2026]

(A) Phosphorus absorption

(B) Nitrogen fixation

(C) Photosynthesis

(D) Carbohydrate storage

133. Which helps in maintaining soil fertility?

(A) Chemical fertilizer

(B) Bio-fertilizer

(C) Pesticide

(D) None of these

134. What is a feature of Xerophytic plants? [2026]

(A) Succulent stem

(B) Spiny leaves

(C) Sunken stomata

(D) All of the above

135. Parasites that live inside the host body are: [2026]

(A) Ectoparasites

(B) Endoparasites

(C) Commensals

(D) Saprophytes

136. Tapeworm is an example of: [2026]

(A) Ectoparasite

(B) Endoparasite

(C) Commensal

(D) Predator

137. Attributes of a population include: [2026]

(A) Birth rate

(B) Death rate

(C) Sex ratio

(D) All of these

138. Where is energy highest in an ecosystem? [2026]

(A) Producer level

(B) Primary consumer

(C) Secondary consumer

(D) Decomposer

139. Helotism is seen in: [2026]

(A) Lichen

(B) Parasitism

(C) Commensalism

(D) None of these

140. In deserts, leaves are modified into: [2026]

(A) Thorns

(B) Flowers

(C) Roots

(D) None of these

141. ‘Immigration’ in a population leads to:

(A) Decrease in density

(B) Increase in density

(C) Stability

(D) None of these

142. Which layer prevents UV rays from reaching earth? [2017A]

(A) $CO_{2}$

(B) Ozone

(C) $CH_{4}$

(D) Oxygen

143. Who first used the term ‘Ecosystem’?

(A) Tansley

(B) Odum

(C) Elton

(D) Haeckel

144. Interspecific interaction occurs: [2026]

(A) Between two different species

(B) Within the same species

(C) Both

(D) None

145. Biosphere means: [2026]

(A) Part of earth where life exists

(B) Only marine part

(C) Only terrestrial part

(D) None of these