1. The biosphere refers to____________.
A) The layer of gases surrounding the Earth
B) The totality of life and life-supporting zones on Earth
C) The Earth’s outer crust
D) The hydrological cycle
Answer: B
Explanation: Biosphere includes all organisms and the parts of the lithosphere, atmosphere, and hydrosphere where life exists.
2. Which is considered the “largest ecosystem”?
A) Forest
B) Desert
C) Ocean
D) Grassland
Answer: C
Explanation: Oceans cover about 71% of the Earth’s surface and are the largest ecosystem supporting diverse life forms.
3. The upper limit of the biosphere is restricted by____________.
A) Availability of oxygen
B) Availability of water
C) Availability of sunlight
D) Temperature and radiation
Answer: D
Explanation: Life is absent beyond ~10 km above sea level due to low temperature and high UV radiation.
4. Which of the following is not a biotic component?
A) Plants
B) Animals
C) Microorganisms
D) Soil minerals
Answer: D
Explanation: Soil minerals are abiotic; plants, animals, and microbes are biotic.
5. Which of the following terms describes the functional role of an organism in an ecosystem?
A) Habitat
B) Niche
C) Community
D) Biome
Answer: B
Explanation: Niche refers to the role and function of a species in its ecosystem.
6. The natural place of an organism or community is called____________.
A) Habitat
B) Ecosystem
C) Ecotone
D) Biome
Answer: A
Explanation: Habitat is the physical environment where an organism lives.
7. The boundary where two ecosystems meet and integrate is called____________.
A) Ecotone
B) Niche
C) Biome
D) Biosphere
Answer: A
Explanation: Ecotone is a transitional zone with species from both ecosystems, often highly productive.
8. Which of the following is an abiotic factor?
A) Decomposers
B) Climate
C) Herbivores
D) Carnivores
Answer: B
Explanation: Climate is non-living (abiotic), while others are biotic.
9. The grassland ecosystem of Africa is known as____________.
A) Pampas
B) Velds
C) Steppes
D) Savanna
Answer: D
Explanation: African tropical grasslands are called Savannas.
10. Which biome is characterized by permafrost?
A) Desert
B) Tundra
C) Taiga
D) Savanna
Answer: B
Explanation: Tundra has permanently frozen subsoil called permafrost.
11. The “lungs of the Earth” are____________.
A) Taiga forests
B) Amazon rainforest
C) Coral reefs
D) Savannas
Answer: B
Explanation: Amazon rainforest produces ~20% of Earth’s oxygen, hence called Earth’s lungs.
12. Which of the following is a producer in an ecosystem?
A) Fungi
B) Bacteria
C) Green plants
D) Vultures
Answer: C
Explanation: Green plants synthesize food via photosynthesis, acting as producers.
13. The transfer of energy from producers to herbivores to carnivores is called____________.
A) Food web
B) Ecological pyramid
C) Food chain
D) Trophic cycle
Answer: C
Explanation: Food chain shows linear energy transfer among organisms.
14. In the energy flow of ecosystems, the maximum energy is found at____________.
A) Producers
B) Primary consumers
C) Secondary consumers
D) Tertiary consumers
Answer: A
Explanation: Producers capture solar energy and form the base of the food chain.
15. Pyramid of numbers in a grassland ecosystem is____________.
A) Inverted
B) Upright
C) Spindle-shaped
D) Irregular
Answer: B
Explanation: Producers are more numerous than herbivores, which are more than carnivores.
16. Which nutrient cycle does not have an atmospheric component?
A) Nitrogen cycle
B) Carbon cycle
C) Phosphorus cycle
D) Oxygen cycle
Answer: C
Explanation: Phosphorus mainly cycles through rocks, soil, and organisms, not atmosphere.
17. The concept of “ecological niche” was first introduced by____________.
A) Charles Darwin
B) G.E. Hutchinson
C) Grinnell
D) Odum
Answer: C
Explanation: Joseph Grinnell (1917) first defined the concept of niche.
18. Which of the following is a keystone species?
A) Tiger in a forest
B) Elephant in a grassland
C) Lion in a savanna
D) All of these
Answer: D
Explanation: Keystone species regulate ecosystem balance; their removal causes collapse.
19. The study of interactions between organisms and environment is called____________.
A) Ecology
B) Biology
C) Environment Science
D) Geology
Answer: A
Explanation: Ecology is the branch of science studying organism–environment interactions.
20. Which of the following is an example of an ecotone?
A) Mangrove forests
B) Desert
C) Ocean
D) Grassland
Answer: A
Explanation: Mangroves occur at the junction of land and sea, hence ecotone.
21. The zone of transition between two ecosystems is usually____________.
A) Less diverse
B) More diverse and productive
C) Having no organisms
D) Identical to the larger ecosystem
Answer: B
Explanation: Ecotone has high diversity due to presence of species from both ecosystems.
22. Which of the following biomes has the greatest biodiversity?
A) Desert
B) Tropical rainforest
C) Tundra
D) Taiga
Answer: B
Explanation: Tropical rainforests have highest species diversity due to favorable conditions.
23. The term “Biomagnification” refers to____________.
A) Increase in population of organisms
B) Increase in size of organisms
C) Increase in concentration of pollutants in higher trophic levels
D) Increase in biodiversity
Answer: C
Explanation: Biomagnification is accumulation of toxins (e.g., DDT) in food chains.
24. Which is the largest carbon reservoir on Earth?
A) Atmosphere
B) Forests
C) Oceans
D) Fossil fuels
Answer: C
Explanation: Oceans store maximum carbon in dissolved form.
25. Which ecosystem has the highest productivity?
A) Desert
B) Grassland
C) Estuary
D) Tundra
Answer: C
Explanation: Estuaries are highly productive ecosystems due to nutrient-rich waters.
26. Which of the following is the study of distribution of organisms on Earth?
A) Ecology
B) Taxonomy
C) Biogeography
D) Paleontology
Answer: C
Explanation: Biogeography deals with spatial and temporal distribution of plants and animals.
27. Who introduced the term “ecosystem”?
A) Ernst Haeckel
B) A.G. Tansley
C) Odum
D) Darwin
Answer: B
Explanation: In 1935, A.G. Tansley coined the term “ecosystem” to describe the interaction of organisms with their environment.
28. The largest terrestrial biome on Earth is____________.
A) Tropical rainforest
B) Taiga (Boreal forest)
C) Savanna
D) Desert
Answer: B
Explanation: Taiga, also known as boreal forest, covers vast areas of North America, Europe, and Asia.
29. Which of the following is not a greenhouse gas?
A) CO₂
B) CH₄
C) O₃
D) O₂
Answer: D
Explanation: Oxygen does not trap heat, unlike CO₂, methane, and ozone.
30. In ecological succession, the first species to colonize an area are called____________.
A) Primary consumers
B) Climax species
C) Pioneer species
D) Secondary species
Answer: C
Explanation: Pioneer species (like lichens, mosses) begin colonization in bare or new areas.
31. The climax community in tropical regions is usually____________.
A) Grassland
B) Desert shrubs
C) Rainforest
D) Tundra
Answer: C
Explanation: In humid tropical climates, succession culminates in dense rainforests.
32. Which of the following ecosystems is least productive?
A) Coral reefs
B) Tundra
C) Tropical rainforest
D) Estuary
Answer: B
Explanation: Due to low temperature and short growing season, tundra has least productivity.
33. The natural vegetation of Mediterranean climate is called____________.
A) Taiga
B) Chaparral
C) Savanna
D) Prairie
Answer: B
Explanation: Mediterranean scrub vegetation is known as chaparral, dominated by shrubs.
34. Coral reefs are found in____________.
A) Cold polar waters
B) Warm shallow tropical seas
C) Deep oceans
D) Freshwater lakes
Answer: B
Explanation: Corals need sunlight and warm saline water to thrive.
35. The main source of energy in an ecosystem is____________.
A) Plants
B) Sun
C) Soil
D) Decomposers
Answer: B
Explanation: Solar energy is the primary source, captured by producers.
36. Which type of pyramid is always upright?
A) Pyramid of numbers
B) Pyramid of biomass
C) Pyramid of energy
D) Pyramid of productivity
Answer: C
Explanation: Energy decreases at each trophic level; hence, energy pyramid is always upright.
37. Biodiversity hotspots are rich in____________.
A) Endemic species
B) Soil minerals
C) Fossil fuels
D) Exotic plants
Answer: A
Explanation: Hotspots are regions with high endemic species under threat.
38. India is part of how many global biodiversity hotspots?
A) 2
B) 3
C) 4
D) 5
Answer: B
Explanation: India has 3 hotspots: Indo-Burma, Himalaya, and Indo-Malayan (Nicobar).
39. The greatest threat to biodiversity is____________.
A) Overgrazing
B) Habitat destruction
C) Hunting
D) Pollution
Answer: B
Explanation: Deforestation, urbanization, and agriculture lead to maximum biodiversity loss.
40. The pyramid of numbers in a forest ecosystem is____________.
A) Upright
B) Inverted
C) Spindle-shaped
D) Irregular
Answer: B
Explanation: Few trees support many herbivores and even more insects, giving inverted shape.
41. Mangroves are found in____________.
A) Tropical rainforests
B) Coastal tidal zones
C) High mountains
D) Grasslands
Answer: B
Explanation: Mangroves thrive in saline tidal waters of tropical coasts.
42. Which biome is known as the “breadbasket of the world”?
A) Tundra
B) Taiga
C) Temperate grassland
D) Desert
Answer: C
Explanation: Fertile temperate grasslands (prairies, pampas, steppes) are ideal for agriculture.
43. In the nitrogen cycle, atmospheric nitrogen is fixed by____________.
A) Fungi
B) Bacteria
C) Plants
D) Animals
Answer: B
Explanation: Rhizobium and cyanobacteria convert nitrogen into usable forms.
44. Which biome has the lowest annual rainfall?
A) Desert
B) Grassland
C) Savanna
D) Taiga
Answer: A
Explanation: Deserts receive less than 25 cm rainfall annually.
45. Which of the following organisms is a decomposer?
A) Earthworm
B) Fungi
C) Lion
D) Goat
Answer: B
Explanation: Fungi decompose organic matter into nutrients.
46. Which is the richest biome in terms of species diversity?
A) Taiga
B) Tropical rainforest
C) Desert
D) Grassland
Answer: B
Explanation: Rainforests harbor more than half of Earth’s plant and animal species.
47. The gradual change in species composition in an area is known as____________.
A) Evolution
B) Mutation
C) Succession
D) Speciation
Answer: C
Explanation: Ecological succession is the natural replacement of communities over time.
48. Which of the following is not a renewable resource?
A) Forests
B) Water
C) Coal
D) Wildlife
Answer: C
Explanation: Coal takes millions of years to form; hence, it is non-renewable.
49. The Antarctic ecosystem is characterized by____________.
A) High productivity
B) Low biodiversity
C) Dense forests
D) Tropical vegetation
Answer: B
Explanation: Harsh climate limits species diversity in Antarctica.
50. The zone of life on Earth is restricted to____________.
A) 6 km above to 6 km below the surface
B) 20 km above to 5 km below
C) 10 km above to 10 km below
D) 15 km above to 5 km below
Answer: A
Explanation: The biosphere extends roughly 6 km above sea level (troposphere) to 6 km below (deep ocean).
51. The area where freshwater and seawater mix is called____________.
A) Lagoon
B) Estuary
C) Delta
D) Fjord
Answer: B
Explanation: Estuaries form at river mouths where freshwater mixes with saline seawater, creating highly productive ecosystems.
52. Which of the following ecosystems has the highest net primary productivity (NPP)?
A) Desert
B) Coral reef
C) Tundra
D) Savanna
Answer: B
Explanation: Coral reefs are highly productive ecosystems due to abundant sunlight and nutrient recycling.
53. Which gas is most important for photosynthesis in plants?
A) Oxygen
B) Nitrogen
C) Carbon dioxide
D) Methane
Answer: C
Explanation: Plants use CO₂ along with sunlight and water to make glucose during photosynthesis.
54. Which of the following is an example of mutualism?
A) Lichen
B) Tapeworm in human intestine
C) Lion eating deer
D) Mosquito feeding on blood
Answer: A
Explanation: Lichen is a symbiotic association between algae (provides food) and fungi (provides shelter).
55. The concept of “ecological pyramid” was given by____________.
A) Charles Elton
B) Darwin
C) E.P. Odum
D) Tansley
Answer: A
Explanation: Charles Elton (1927) proposed ecological pyramids to represent energy/biomass/number relationships.
56. Which of the following is an in-situ method of biodiversity conservation?
A) Zoological parks
B) Botanical gardens
C) Wildlife sanctuaries
D) Seed banks
Answer: C
Explanation: In-situ conservation means protecting species in their natural habitats, like sanctuaries and national parks.
57. Which of the following is an ex-situ method of biodiversity conservation?
A) Biosphere reserves
B) National parks
C) Botanical gardens
D) Sacred groves
Answer: C
Explanation: Ex-situ conservation involves protecting species outside their natural habitat, e.g., zoos, seed banks, gardens.
58. Which of the following is a Ramsar site in India?
A) Loktak Lake
B) Vembanad Lake
C) Chilika Lake
D) All of these
Answer: D
Explanation: Loktak (Manipur), Vembanad (Kerala), and Chilika (Odisha) are Ramsar wetlands of international importance.
59. Which Indian biosphere reserve is part of UNESCO World Network of Biosphere Reserves?
A) Nilgiri
B) Nanda Devi
C) Sundarbans
D) All of these
Answer: D
Explanation: Nilgiri, Nanda Devi, and Sundarbans are UNESCO-recognized biosphere reserves.
60. The primary producers in an ocean ecosystem are____________.
A) Fishes
B) Phytoplankton
C) Zooplankton
D) Seaweed only
Answer: B
Explanation: Phytoplankton are microscopic plants that photosynthesize and form the base of oceanic food chains.
61. Which is the most abundant gas in the atmosphere?
A) Oxygen
B) Nitrogen
C) Carbon dioxide
D) Argon
Answer: B
Explanation: Nitrogen makes up 78% of the Earth’s atmosphere.
62. Which forest type has the maximum biomass?
A) Tropical rainforests
B) Temperate grasslands
C) Coniferous forests
D) Mangroves
Answer: A
Explanation: Due to warm climate and heavy rainfall, tropical rainforests have highest biomass per unit area.
63. Which zone of a lake supports rooted vegetation?
A) Littoral zone
B) Limnetic zone
C) Profundal zone
D) Benthic zone
Answer: A
Explanation: The shallow littoral zone has enough light penetration for rooted plants.
64. The term “Gaia Hypothesis” (Earth as a living system) was proposed by____________.
A) James Lovelock
B) Charles Darwin
C) Alfred Wallace
D) Odum
Answer: A
Explanation: Lovelock’s Gaia hypothesis suggests Earth functions as a self-regulating living system.
65. The main factor limiting plant growth in deserts is____________.
A) High temperature
B) Low sunlight
C) Low water availability
D) Poor soil nutrients
Answer: C
Explanation: Scarcity of water is the primary limiting factor in desert plant growth.
66. Which of the following ecosystems is known as “cradle of evolution”?
A) Coral reefs
B) Tropical rainforest
C) Wetlands
D) Estuaries
Answer: A
Explanation: Coral reefs provide diverse niches and have high species richness, earning them the title “cradle of evolution.”
67. What is the main source of oxygen in the atmosphere?
A) Weathering of rocks
B) Photosynthesis
C) Volcanic activity
D) Fossil fuels
Answer: B
Explanation: Green plants and phytoplankton release oxygen as a by-product of photosynthesis.
68. Which of the following forests is also called “Taiga”?
A) Tropical rainforest
B) Coniferous forest
C) Temperate deciduous forest
D) Mangroves
Answer: B
Explanation: Taiga refers to coniferous forests of cold temperate regions.
69. Which is the largest terrestrial carbon sink?
A) Forests
B) Soil organic matter
C) Permafrost
D) Fossil fuels
Answer: A
Explanation: Forests act as major carbon sinks through photosynthesis and biomass storage.
70. Which of the following human activities increases desertification?
A) Overgrazing
B) Deforestation
C) Over-irrigation
D) All of these
Answer: D
Explanation: Overgrazing, deforestation, and excessive irrigation lead to land degradation and desertification.
71. Which ecosystem is called the “ecological supermarket”?
A) Grassland
B) Estuary
C) Tropical rainforest
D) Savanna
Answer: B
Explanation: Estuaries are highly productive, providing food and nutrients for many species.
72. Which species concept focuses on reproductive isolation?
A) Ecological concept
B) Morphological concept
C) Biological concept
D) Evolutionary concept
Answer: C
Explanation: The biological species concept (Ernst Mayr) defines species by reproductive isolation.
73. Which type of succession begins on a bare rock surface?
A) Primary succession
B) Secondary succession
C) Tertiary succession
D) Climax succession
Answer: A
Explanation: Primary succession begins in lifeless areas like bare rocks, with lichens and mosses as pioneers.
74. Which biome is characterized by trees shedding leaves in dry season?
A) Tropical deciduous forest
B) Temperate coniferous forest
C) Taiga
D) Tropical rainforest
Answer: A
Explanation: These forests shed leaves to conserve water during dry seasons.
75. The “edge effect” (higher diversity at ecosystem boundaries) is most prominent in____________.
A) Ecotones
B) Climax community
C) Desert
D) Tundra
Answer: A
Explanation: Ecotones show edge effect, with higher diversity and abundance than adjoining ecosystems.
76. Which of the following is a natural greenhouse gas?
A) Nitrous oxide (N₂O)
B) Methane (CH₄)
C) Carbon dioxide (CO₂)
D) All of these
Answer: D
Explanation: CO₂, CH₄, and N₂O are natural greenhouse gases responsible for trapping heat in the atmosphere.
77. Which biome is dominated by coniferous trees like pine, spruce, and fir?
A) Taiga
B) Tundra
C) Desert
D) Grassland
Answer: A
Explanation: The Taiga biome is dominated by cold-tolerant coniferous forests.
78. Which of the following is an endangered species found in India?
A) Asiatic Lion
B) Bengal Tiger
C) One-horned Rhinoceros
D) All of these
Answer: D
Explanation: Asiatic Lion, Bengal Tiger, and One-horned Rhino are endangered and protected under Indian wildlife laws.
79. The main function of ozone in the stratosphere is____________.
A) To produce rainfall
B) To absorb harmful UV radiation
C) To increase Earth’s temperature
D) To trap methane
Answer: B
Explanation: The ozone layer protects life by absorbing UV-B and UV-C radiation.
80. The “Biotic potential” of a species refers to____________.
A) Maximum reproductive capacity under ideal conditions
B) Population decline due to limited resources
C) Carrying capacity of environment
D) None of these
Answer: A
Explanation: Biotic potential measures maximum growth rate of a species without limiting factors.
81. Which of the following is not a renewable resource?
A) Solar energy
B) Water
C) Petroleum
D) Forests
Answer: C
Explanation: Petroleum is non-renewable as it takes millions of years to form.
82. The interaction in which one species benefits and the other is unaffected is called____________.
A) Mutualism
B) Commensalism
C) Parasitism
D) Predation
Answer: B
Explanation: In commensalism, one species benefits while the other is neither harmed nor benefited.
83. In the food chain, herbivores are____________.
A) Producers
B) Primary consumers
C) Secondary consumers
D) Decomposers
Answer: B
Explanation: Herbivores feed directly on producers (plants), making them primary consumers.
84. The term “biodiversity hotspot” was coined by____________.
A) Edward Wilson
B) Norman Myers
C) Alfred Wallace
D) Charles Darwin
Answer: B
Explanation: Norman Myers (1988) introduced the term “biodiversity hotspot” for areas rich in endemic and threatened species.
85. The Sundarbans mangrove forest is famous for____________.
A) Asiatic Lion
B) Royal Bengal Tiger
C) Snow Leopard
D) Great Indian Bustard
Answer: B
Explanation: Sundarbans is the world’s largest mangrove forest, home to Bengal tigers.
86. Which of the following cycles is a sedimentary cycle?
A) Nitrogen cycle
B) Carbon cycle
C) Phosphorus cycle
D) Oxygen cycle
Answer: C
Explanation: Phosphorus cycle is sedimentary, as it mainly involves soil and rock minerals.
87. Which of the following is a desert adaptation in plants?
A) Thick cuticle
B) Sunken stomata
C) Deep roots
D) All of these
Answer: D
Explanation: Desert plants (xerophytes) adapt through cuticles, sunken stomata, and deep root systems.
88. The gradual decrease in energy through trophic levels is due to____________.
A) Respiration
B) Heat loss
C) Metabolic processes
D) All of these
Answer: D
Explanation: At each trophic level, energy is lost as heat and through metabolism, reducing energy availability upwards.
89. Which Indian biosphere reserve is famous for “floating vegetation”?
A) Nanda Devi
B) Loktak Lake
C) Sundarbans
D) Nilgiris
Answer: B
Explanation: Loktak Lake (Manipur) has floating biomass called Phumdis.
90. Which Indian sanctuary is known as the “Bird Watcher’s Paradise”?
A) Bharatpur (Keoladeo)
B) Gir National Park
C) Kaziranga
D) Jim Corbett
Answer: A
Explanation: Keoladeo Ghana Bird Sanctuary in Rajasthan is famous for migratory birds.
91. The process of nutrient enrichment of water bodies leading to algal bloom is called____________.
A) Salinization
B) Desertification
C) Eutrophication
D) Bioaccumulation
Answer: C
Explanation: Excess nutrients (nitrates, phosphates) cause algal blooms, depleting oxygen in water.
92. Which biome is also called the “cold desert”?
A) Tundra
B) Taiga
C) Savanna
D) Grassland
Answer: A
Explanation: Tundra is known as “cold desert” due to low precipitation and extreme cold.
93. Which of the following is a non-point source of water pollution?
A) Industrial discharge
B) Sewage outfall
C) Agricultural runoff
D) Oil spill
Answer: C
Explanation: Non-point sources are diffuse and not easily traceable, like fertilizers from farms.
94. Which is the largest mangrove forest in the world?
A) Florida Everglades
B) Amazon delta
C) Sundarbans
D) Mekong delta
Answer: C
Explanation: Sundarbans in India and Bangladesh form the largest mangrove ecosystem.
95. The carrying capacity of an ecosystem refers to____________.
A) Maximum population that can be supported sustainably
B) Total biodiversity of the system
C) Net productivity of the system
D) Number of species present
Answer: A
Explanation: Carrying capacity is the maximum population size that environment can sustain.
96. Which Indian national park is famous for one-horned rhinoceros?
A) Gir
B) Kaziranga
C) Jim Corbett
D) Ranthambore
Answer: B
Explanation: Kaziranga National Park in Assam is home to the world’s largest population of one-horned rhinoceros.
97. The Great Barrier Reef is located in____________.
A) Pacific Ocean
B) Atlantic Ocean
C) Indian Ocean
D) Arctic Ocean
Answer: A
Explanation: The Great Barrier Reef lies off the coast of Queensland, Australia, in the Pacific Ocean.
98. Which of the following is a primary pollutant?
A) Ozone
B) Peroxyacetyl nitrate (PAN)
C) Sulphur dioxide (SO₂)
D) Smog
Answer: C
Explanation: SO₂ is directly emitted from sources (primary), while ozone and PAN are secondary pollutants.
99. Which country hosts the largest area of tropical rainforest?
A) Indonesia
B) Brazil
C) Congo (DRC)
D) India
Answer: B
Explanation: Brazil contains the largest share of the Amazon rainforest.
100. Which of the following best describes the biosphere?
A) A thin zone of Earth where life exists
B) A single ecosystem
C) Only terrestrial life forms
D) Only aquatic life forms
Answer: A
Explanation: Biosphere is the global sum of ecosystems, comprising land, water, and air where life exists.