NCERT NEET Biology English Medium Part-1 | Chapter 31 : Ecosystem

NCERT NEET Biology English Medium Part-1 | Chapter 31 : Ecosystem

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Question 1. Which of the following is considered the functional unit of nature, where living organisms interact among themselves and with the surrounding physical environment?

1. Biosphere.
2. Community.
3. Ecosystem.
4. Population.

Answer: c.

Question 2. Which of the following is an example of a man-made ecosystem?

1. Estuary.
2. Coral reef.
3. Crop field.
4. Grassland.

Answer: c.

Question 3. Vertical distribution of different species occupying different levels in an ecosystem is called?

1. Stratification.
2. Eutrophication.
3. Succession.
4. Fragmentation.

Answer: a.

Question 4. In a forest ecosystem, which of the following occupies the top vertical strata or layer?

1. Herbs.
2. Shrubs.
3. Trees.
4. Mosses.

Answer: c.

Question 5. The rate of biomass production per unit area over a time period by plants during photosynthesis is called?

1. Gross primary productivity.
2. Net primary productivity.
3. Secondary productivity.
4. Primary production.

Answer: d.

Question 6. What is the relationship between Gross Primary Productivity (GPP) and Net Primary Productivity (NPP)?

1. GPP = NPP + Respiration losses (R).
2. NPP = GPP + Respiration losses (R).
3. GPP = NPP / Respiration losses (R).
4. NPP = GPP x Respiration losses (R).

Answer: a.

Question 7. The rate of formation of new organic matter by consumers is known as?

1. Net primary productivity.
2. Gross primary productivity.
3. Secondary productivity.
4. Tertiary productivity.

Answer: c.

Question 8. The annual net primary productivity of the whole biosphere is approximately how much dry weight of organic matter?

1. 170 billion tons.
2. 55 billion tons.
3. 120 billion tons.
4. 100 billion tons.

Answer: a.

Question 9. Despite occupying about 70 percent of the surface, the productivity of the oceans is only about?

1. 170 billion tons.
2. 55 billion tons.
3. 115 billion tons.
4. 20 billion tons.

Answer: b.

Question 10. Which process involves detritivores breaking down detritus into smaller particles?

1. Catabolism.
2. Humification.
3. Fragmentation.
4. Leaching.

Answer: c.

Question 11. By which process do water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts?

1. Fragmentation.
2. Leaching.
3. Catabolism.
4. Mineralisation.

Answer: b.

Question 12. Bacterial and fungal enzymes degrade detritus into simpler inorganic substances through which process?

1. Catabolism.
2. Leaching.
3. Humification.
4. Fragmentation.

Answer: a.

Question 13. Which of the following is a dark-coloured amorphous substance that is highly resistant to microbial action and undergoes decomposition at an extremely slow rate?

1. Detritus.
2. Humus.
3. Silt.
4. Loam.

Answer: b.

Question 14. The degradation of humus by some microbes leading to the release of inorganic nutrients is called?

1. Humification.
2. Fragmentation.
3. Mineralisation.
4. Catabolism.

Answer: c.

Question 15. The rate of decomposition is slower if detritus is rich in?

1. Nitrogen and water-soluble substances.
2. Sugars and nitrogen.
3. Lignin and chitin.
4. Proteins and nucleic acids.

Answer: c.

Question 16. Which of the following climatic factors most strongly regulate decomposition through their effects on soil microbes?

1. Temperature and soil moisture.
2. Wind speed and sunlight.
3. Light intensity and day length.
4. Atmospheric pressure and altitude.

Answer: a.

Question 17. Of the incident solar radiation, what percentage is Photosynthetically Active Radiation (PAR)?

1. Less than 50 percent.
2. Exactly 50 percent.
3. More than 50 percent.
4. 100 percent.

Answer: a.

Question 18. Plants capture what percentage of the Photosynthetically Active Radiation (PAR)?

1. 10-20 percent.
2. 2-10 percent.
3. 1-2 percent.
4. 50-60 percent.

Answer: b.

Question 19. In a grazing food chain (GFC), the first trophic level is always occupied by?

1. Herbivores.
2. Primary carnivores.
3. Producers.
4. Secondary consumers.

Answer: c.

Question 20. The detritus food chain (DFC) begins with which of the following?

1. Living green plants.
2. Dead organic matter.
3. Herbivores.
4. Carnivores.

Answer: b.

Question 21. Organisms that feed on dead organic matter and meet their energy and nutrient requirements by degrading it are known as?

1. Autotrophs.
2. Herbivores.
3. Saprotrophs.
4. Primary consumers.

Answer: c.

Question 22. In an aquatic ecosystem, which is the major conduit for energy flow?

1. Detritus food chain.
2. Grazing food chain.
3. Parasitic food chain.
4. Saprophytic food chain.

Answer: b.

Question 23. In a terrestrial ecosystem, a much larger fraction of energy flows through which food chain?

1. Grazing food chain.
2. Detritus food chain.
3. Parasitic food chain.
4. Aquatic food chain.

Answer: b.

Question 24. The natural interconnection of food chains forms a?

1. Food web.
2. Trophic level.
3. Ecological pyramid.
4. Seral community.

Answer: a.

Question 25. Based on the source of their nutrition or food, organisms occupy a specific place in the food chain known as their?

1. Strata.
2. Trophic level.
3. Ecological niche.
4. Sere.

Answer: b.

Question 26. Each trophic level has a certain mass of living material at a particular time called as?

1. Standing state.
2. Net productivity.
3. Standing crop.
4. Gross productivity.

Answer: c.

Question 27. The 10 per cent law of energy transfer from one trophic level to the next was given by?

1. Tansley.
2. Lindeman.
3. Odum.
4. Elton.

Answer: b.

Question 28. In ecological pyramids, the base always represents the?

1. Primary consumers.
2. Secondary consumers.
3. Producers.
4. Top carnivores.

Answer: c.

Question 29. The pyramid of numbers in a grassland ecosystem is typically?

1. Inverted.
2. Spindle-shaped.
3. Upright.
4. Urn-shaped.

Answer: c.

Question 30. An inverted pyramid of biomass can be observed in which of the following ecosystems?

1. Forest.
2. Grassland.
3. Tree.
4. Pond.

Answer: d.

Question 31. Which ecological pyramid is always upright and can never be inverted?

1. Pyramid of numbers.
2. Pyramid of biomass.
3. Pyramid of energy.
4. Pyramid of species.

Answer: c.

Question 32. In an ecosystem, birds that eat both seeds and insects occupy how many trophic levels simultaneously?

1. One.
2. Two.
3. Three.
4. Four.

Answer: b.

Question 33. Ecological pyramids do not accommodate which of the following groups of organisms despite their vital role in the ecosystem?

1. Primary consumers.
2. Top carnivores.
3. Saprophytes.
4. Herbivores.

Answer: c.

Question 34. The gradual and fairly predictable change in the species composition of a given area is called?

1. Ecological succession.
2. Stratification.
3. Eutrophication.
4. Biomagnification.

Answer: a.

Question 35. The entire sequence of communities that successively change in a given area are called?

1. Pioneer species.
2. Climax community.
3. Sere(s).
4. Ecotone.

Answer: c.

Question 36. Succession that begins in an area where no living organisms ever existed is called?

1. Primary succession.
2. Secondary succession.
3. Autogenic succession.
4. Allogenic succession.

Answer: a.

Question 37. Which of the following is an example of an area where primary succession occurs?

1. Abandoned farm lands.
2. Burned or cut forests.
3. Newly cooled lava.
4. Lands that have been flooded.

Answer: c.

Question 38. Which type of succession is relatively faster?

1. Primary succession.
2. Secondary succession.
3. Xerarch succession.
4. Hydrarch succession.

Answer: b.

Question 39. Succession that takes place in water areas and progresses from hydric to mesic conditions is known as?

1. Xerarch succession.
2. Hydrarch succession.
3. Psammosere.
4. Halosere.

Answer: b.

Question 40. The species that invade a bare area first are known as?

1. Climax species.
2. Seral species.
3. Pioneer species.
4. Keystone species.

Answer: c.

Question 41. In primary succession on rocks, the pioneer species are usually?

1. Mosses.
2. Lichens.
3. Ferns.
4. Phytoplankton.

Answer: b.

Question 42. In primary succession in water, the pioneer species are typically?

1. Free-floating angiosperms.
2. Small phytoplankton.
3. Rooted hydrophytes.
4. Sedges.

Answer: b.

Question 43. Both hydrarch and xerarch successions lead to which type of climax community?

1. Xeric.
2. Hydric.
3. Mesic.
4. Halophytic.

Answer: c.

Question 44. The climax community remains stable as long as?

1. The environment changes rapidly.
2. The environment remains unchanged.
3. Secondary succession starts.
4. Mutation rates are high.

Answer: b.

Question 45. The amount of nutrients, such as carbon, nitrogen, phosphorus, and calcium, present in the soil at any given time is referred to as?

1. Standing crop.
2. Standing state.
3. Nutrient pool.
4. Climax state.

Answer: b.

Question 46. Another name for nutrient cycling is?

1. Hydrological cycle.
2. Biogeochemical cycle.
3. Rock cycle.
4. Energy cycle.

Answer: b.

Question 47. Nutrient cycles are fundamentally of how many types?

1. One.
2. Two.
3. Three.
4. Four.

Answer: b.

Question 48. The reservoir for gaseous type of nutrient cycle exists in the?

1. Earth's crust.
2. Atmosphere.
3. Ocean floors.
4. Deep rocks.

Answer: b.

Question 49. The reservoir for the sedimentary type of nutrient cycle is located in the?

1. Atmosphere.
2. Earth's crust.
3. Stratosphere.
4. Ionosphere.

Answer: b.

Question 50. What constitutes 49 percent of the dry weight of organisms and is next only to water?

1. Nitrogen.
2. Phosphorus.
3. Carbon.
4. Calcium.

Answer: c.

Question 51. Approximately what percentage of global carbon is found dissolved in oceans?

1. 10 percent.
2. 30 percent.
3. 50 percent.
4. 71 percent.

Answer: d.

Question 52. About how much carbon is fixed in the biosphere through photosynthesis annually?

1. 4 × 10^13 kg.
2. 4 × 10^10 kg.
3. 4 × 10^8 kg.
4. 4 × 10^15 kg.

Answer: a.

Question 53. Which of the following is the major reservoir for phosphorus?

1. Atmosphere.
2. Ocean water.
3. Rocks.
4. Fossil fuels.

Answer: c.

Question 54. Phosphorus is a major constituent of which of the following biological molecules?

1. Carbohydrates.
2. Lipids.
3. Nucleic acids.
4. Proteins.

Answer: c.

Question 55. Herbivores and other animals obtain phosphorus primarily from?

1. Drinking water.
2. Plants.
3. Soil directly.
4. Atmosphere.

Answer: b.

Question 56. The products of ecosystem processes are named as?

1. Biogeochemical cycles.
2. Ecosystem services.
3. Ecological efficiencies.
4. Trophic cascades.

Answer: b.

Question 57. Who and his colleagues tried to put price tags on nature’s life-support services?

1. Robert Brown.
2. Robert Constanza.
3. Paul Ehrlich.
4. Alexander von Humboldt.

Answer: b.

Question 58. The average price tag put on the fundamental ecosystem services a year is about?

1. US $ 33 million.
2. US $ 33 billion.
3. US $ 33 trillion.
4. US $ 133 trillion.

Answer: c.

Question 59. Out of the total cost of various ecosystem services, soil formation accounts for about?

1. 10 percent.
2. 20 percent.
3. 50 percent.
4. 80 percent.

Answer: c.

Question 60. The contributions of ecosystem services like recreation and nutrient cycling are less than?

1. 50 percent each.
2. 25 percent each.
3. 10 percent each.
4. 1 percent each.

Answer: c.

Question 61. The mass of living material at a trophic level at a particular time is expressed as?

1. Dry weight or fresh weight.
2. Rate of energy production.
3. Volume of living organisms.
4. Lifespan of organisms.

Answer: a.

Question 62. The measurement of biomass is more accurate if it is expressed in terms of?

1. Fresh weight.
2. Dry weight.
3. Volume.
4. Cell number.

Answer: b.

Question 63. Which ecosystem shows an inverted pyramid of numbers?

1. Grassland.
2. Forest.
3. Tree ecosystem.
4. Desert.

Answer: c.

Question 64. What is the limitation of ecological pyramids?

1. They assume a simple food chain which almost never exists in nature.
2. They account for the same species belonging to two or more trophic levels.
3. They accommodate the complex food web structure.
4. They incorporate saprophytes at the base.

Answer: a.

Question 65. The sequential stages in a secondary succession are called?

1. Pioneer seral stages.
2. Climax stages.
3. Subsere.
4. Ecoseres.

Answer: c.

Question 66. In hydrarch succession, the rooted-submerged stage is followed by the?

1. Phytoplankton stage.
2. Rooted-floating stage.
3. Reed-swamp stage.
4. Marsh-meadow stage.

Answer: b.

Question 67. During primary succession on rocks, what do lichens secrete to dissolve the rock and help in soil formation?

1. Basic fluids.
2. Acids.
3. Digestive enzymes.
4. Hormones.

Answer: b.

Question 68. The rate of secondary succession is faster than primary succession because?

1. Soil or sediment is already present.
2. It occurs only in aquatic environments.
3. It requires highly adapted pioneer species.
4. The climate changes more rapidly.

Answer: a.

Question 69. Which factor decides the nature of the climax community in both primary and secondary succession?

1. Water depth.
2. Soil pH.
3. Climate.
4. Pioneer species.

Answer: c.

Question 70. There is no respiratory release of which element into the atmosphere?

1. Carbon.
2. Oxygen.
3. Phosphorus.
4. Nitrogen.

Answer: c.

Question 71. The atmospheric inputs of phosphorus through rainfall are?

1. Much larger than carbon inputs.
2. Equal to carbon inputs.
3. Much smaller than carbon inputs.
4. Dependent entirely on local pollution.

Answer: c.

Question 72. Which of the following is not a gaseous biogeochemical cycle?

1. Nitrogen cycle.
2. Carbon cycle.
3. Phosphorus cycle.
4. Oxygen cycle.

Answer: c.

Question 73. Which of the following helps to regulate the rate of release of nutrients into the atmosphere in a nutrient cycle?

1. Climax species.
2. Environmental factors like soil, moisture, pH, and temperature.
3. Number of trophic levels.
4. Standing crop of the ecosystem.

Answer: b.

Question 74. How does carbon return to the atmosphere after being fixed by plants?

1. Through photosynthesis by consumers.
2. By respiratory activities of producers and consumers.
3. Exclusively by the burning of fossil fuels.
4. By precipitation in the oceans.

Answer: b.

Question 75. Decomposers contribute substantially to the carbon cycle by processing?

2. Atmospheric CO2.
3. Dissolved carbon in oceans.
4. Waste materials and dead organic matter.
5. Living plant biomass.

Answer: c.

Question 76. Burning of wood, forest fires, and combustion of organic matter are significant sources of?

1. Calcium release.
2. Phosphorus release.
3. Carbon dioxide release.
4. Nitrogen fixation.

Answer: c.

Question 77. Which element cycle is mainly characterized by the weathering of rocks?

1. Carbon cycle.
2. Nitrogen cycle.
3. Water cycle.
4. Phosphorus cycle.

Answer: d.

Question 78. In the phosphorus cycle, what acts as the natural reservoir?

1. The atmosphere.
2. Phosphate rocks.
3. Dissolved organic matter.
4. Primary producers.

Answer: b.

Question 79. The total requirement of energy by the producers is met by?

1. Decomposers.
2. Solar energy.
3. Chemical energy from rocks.
4. Secondary consumers.

Answer: b.

Question 80. Food chains in nature are interconnected to provide stability to the ecosystem. This interlocking pattern is called?

1. Ecological hierarchy.
2. Food web.
3. Food link.
4. Ecological pyramid.

Answer: b.

Question 81. The mass of living organic matter in a given area at a given time is?

1. Gross primary productivity.
2. Net primary productivity.
3. Standing state.
4. Standing crop.

Answer: d.

Question 82. Which of the following ecosystems has the highest gross primary productivity?

1. Tropical rain forest.
2. Coral reef.
3. Desert.
4. Open ocean.

Answer: a.

Question 83. The rate at which food energy is assimilated at the trophic level of consumers is called?

1. Gross primary productivity.
2. Net primary productivity.
3. Secondary productivity.
4. Tertiary productivity.

Answer: c.

Question 84. Which stage comes after the reed-swamp stage in hydrarch succession?

1. Phytoplankton stage.
2. Rooted-floating stage.
3. Marsh-meadow stage.
4. Scrub stage.

Answer: c.

Question 85. A community that is in near equilibrium with the environment is called?

1. Seral community.
2. Pioneer community.
3. Ecotone community.
4. Climax community.

Answer: d.

Question 86. Which of the following represents the correct sequence of stages in xerarch succession?

1. Lichens -> Bryophytes -> Herbs -> Shrubs -> Trees.
2. Bryophytes -> Lichens -> Herbs -> Shrubs -> Trees.
3. Shrubs -> Herbs -> Lichens -> Bryophytes -> Trees.
4. Lichens -> Herbs -> Bryophytes -> Shrubs -> Trees.

Answer: a.

Question 87. An inverted pyramid of biomass is often found in aquatic ecosystems because?

1. Phytoplankton have a very long lifespan.
2. The biomass of phytoplankton is much higher than zooplankton.
3. Phytoplankton crop is small but has a high turnover rate.
4. Zooplankton do not consume phytoplankton.

Answer: c.

Question 88. In an ecosystem, which of the following acts as a decomposer?

1. Algae.
2. Cyanobacteria.
3. Fungi.
4. Phytoplankton.

Answer: c.

Question 89. Ecosystem services include all of the following EXCEPT?

1. Purification of air and water.
2. Mitigation of droughts and floods.
3. Cycling of nutrients.
4. Depletion of the ozone layer.

Answer: d.

Question 90. Costanza's calculation indicated that the cost of climate regulation and habitat for wildlife are about?

1. 50 percent each.
2. 10 percent each.
3. 6 percent each.
4. 2 percent each.

Answer: c.

Question 91. The amount of energy transferred from one trophic level to the next higher level is typically?

1. 1 percent.
2. 10 percent.
3. 20 percent.
4. 90 percent.

Answer: b.

Question 92. Earthworms are known as the farmer's friends because they help in?

1. Humification.
2. Fragmentation of detritus.
3. Nitrogen fixation.
4. Phosphorus weathering.

Answer: b.

Question 93. Most food chains have a maximum of 4 or 5 trophic levels because?

1. Ecosystems lack enough space.
2. Energy transfer follows the 10 percent law, leaving little energy for higher levels.
3. Predators are heavily hunted.
4. Competition is too high at the top.

Answer: b.

Question 94. The base of the Detritus Food Chain (DFC) is formed by?

1. Green plants.
2. Saprotrophs.
3. Dead leaves and animal remains.
4. Primary consumers.

Answer: c.

Question 95. The amount of solar radiation that reaches the earth's atmosphere is called incident solar radiation. The PAR fraction is what part of the total?

1. 1-5 percent.
2. 2-10 percent.
3. Less than 50 percent.
4. More than 70 percent.

Answer: c.

Question 96. What happens to the rate of decomposition if the soil is kept in anaerobic conditions?

1. It increases significantly.
2. It remains unchanged.
3. It is inhibited.
4. It shifts to fragmentation only.

Answer: c.

Question 97. The structural components of an ecosystem include all EXCEPT?

1. Species composition.
2. Stratification.
3. Nutrient cycling.
4. Distribution of species.

Answer: c.

Question 98. Which element plays an important role in the shells, bones, and teeth of many animals?

1. Nitrogen.
2. Carbon.
3. Phosphorus.
4. Sulfur.

Answer: c.

Question 99. The standing crop is measured as the mass of living organisms or the number in a unit area. The biomass of a standing crop is best measured in terms of?

1. Fresh weight.
2. Dry weight.
3. Water content.
4. Total energy content.

Answer: b.

Question 100. In an ecosystem, which component regulates the flow of energy and the cycling of materials efficiently to maintain a self-sustaining system?

1. Producers alone.
2. Consumers alone.
3. Only climatic factors.
4. Interactions among biotic and abiotic components.

Answer: d.

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