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NCERT Based MCQ with Explanation:
1. What is an ecosystem primarily defined as?
(a) A group of animals living together
(b) A functional unit of nature with interacting organisms and environment
(c) A large forest or sea only
(d) A man-made structure like an aquarium
Explanation: The chapter defines an ecosystem as a functional unit of nature where living organisms interact among themselves and with the surrounding physical environment, making option b the correct choice.
2. Which of the following is NOT an example of a terrestrial ecosystem?
(a) Forest
(b) Grassland
(c) Estuary
(d) Desert
Explanation: The text lists forest, grassland, and desert as terrestrial ecosystems, while estuary is an aquatic ecosystem, making option c incorrect as a terrestrial example.
3. What is the largest ecosystem mentioned in the chapter?
(a) A small pond
(b) A forest
(c) The biosphere
(d) A desert
Explanation: The biosphere is described as a global ecosystem, a composite of all local ecosystems on Earth, making it the largest ecosystem mentioned.
4. Which component of an ecosystem includes water and soil?
(a) Biotic
(b) Abiotic
(c) Producers
(d) Consumers
Explanation: Abiotic components are non-living elements like water, air, and soil, as explained in the ecosystem structure section, distinguishing them from biotic components.
5. What is the term for the vertical distribution of species in an ecosystem?
(a) Species composition
(b) Stratification
(c) Productivity
(d) Decomposition
Explanation: Stratification refers to the vertical layering of species, such as trees at the top, shrubs in the middle, and herbs at the bottom in a forest, as defined in the text.
6. Which of the following is a man-made ecosystem?
(a) Forest
(b) Pond
(c) Aquarium
(d) River
Explanation: The chapter explicitly states that crop fields and aquariums are examples of man-made ecosystems, unlike natural ecosystems like forests or rivers.
7. What is the primary source of energy for most ecosystems?
(a) Wind
(b) Sun
(c) Water
(d) Soil
Explanation: The text specifies that the sun is the only source of energy for all ecosystems on Earth, except for deep-sea hydrothermal ecosystems, making it the primary energy source.
8. Which process involves the conversion of inorganic material into organic material by autotrophs?
(a) Decomposition
(b) Energy flow
(c) Photosynthesis
(d) Nutrient cycling
Explanation: Autotrophs, such as plants, use photosynthesis to convert inorganic materials (like carbon dioxide and water) into organic matter using solar energy, as described in the chapter.
9. In a forest ecosystem, what occupies the top vertical strata?
(a) Herbs
(b) Shrubs
(c) Trees
(d) Grasses
Explanation: The text explains that in a forest, trees occupy the top vertical strata, followed by shrubs and then herbs and grasses at lower levels.
10. Which of the following is an abiotic component of a pond ecosystem?
(a) Phytoplankton
(b) Zooplankton
(c) Water
(d) Bacteria
Explanation: Water is an abiotic (non-living) component, while phytoplankton, zooplankton, and bacteria are biotic (living) components, as per the pond example in the text.
11. What regulates the rate of function in a pond ecosystem?
(a) Consumers
(b) Solar input and climatic conditions
(c) Decomposers
(d) Autotrophs only
Explanation: The chapter states that solar input, temperature cycles, day-length, and other climatic conditions regulate the functioning of a pond ecosystem.
12. Which organisms are considered autotrophs in a pond ecosystem?
(a) Zooplankton
(b) Phytoplankton and algae
(c) Bacteria
(d) Fungi
Explanation: Phytoplankton, algae, and certain plants are autotrophs because they produce their own food via photosynthesis, as noted in the pond example.
13. What is the role of decomposers in an ecosystem?
(a) Produce food
(b) Break down dead matter into inorganic substances
(c) Consume autotrophs
(d) Transfer energy to higher trophic levels
Explanation: Decomposers like fungi and bacteria break down complex organic matter into simpler inorganic substances, as explained in the decomposition section.
14. What type of energy movement is characteristic of ecosystems?
(a) Bidirectional
(b) Unidirectional
(c) Circular
(d) Random
Explanation: The chapter emphasizes that energy flows unidirectionally from the sun to producers, then to consumers, and is lost as heat, never returning to its source.
15. What is primary production defined as?
(a) The rate of energy loss
(b) The amount of biomass produced by plants during photosynthesis
(c) The energy consumed by heterotrophs
(d) The decomposition rate
Explanation: Primary production is the amount of biomass or organic matter produced by plants during photosynthesis, as defined in the productivity section.
NCERT Science MCQ - Class- 9th16. How is productivity typically expressed?
(a) Weight (gm⁻²) or energy (kcal m⁻²)
(b) Number of organisms
(c) Volume of water
(d) Temperature degrees
Explanation: The text states that productivity is expressed in terms of weight (gm⁻²) or energy (kcal m⁻²), allowing comparison across ecosystems.
17. What is the relationship between GPP and NPP?
(a) GPP + R = NPP
(b) GPP - R = NPP
(c) NPP - R = GPP
(d) GPP = NPP
Explanation: Gross primary productivity (GPP) minus respiration losses (R) equals net primary productivity (NPP), as per the formula provided in the text.
18. What does net primary productivity (NPP) represent?
(a) Total energy produced by plants
(b) Biomass available for consumption by heterotrophs
(c) Energy lost as heat
(d) Rate of decomposition
Explanation: NPP is the biomass remaining after plant respiration, available for herbivores and decomposers, as explained in the productivity section.
19. What is secondary productivity?
(a) Biomass produced by plants
(b) Rate of formation of organic matter by consumers
(c) Energy lost in decomposition
(d) Rate of nutrient cycling
Explanation: Secondary productivity is defined as the rate at which consumers (heterotrophs) form new organic matter, distinct from plant-based primary productivity.
20. Which factor does NOT affect primary productivity?
(a) Plant species
(b) Nutrient availability
(c) Photosynthetic capacity
(d) Number of decomposers
Explanation: Primary productivity depends on plant species, nutrients, and photosynthetic capacity, not directly on decomposers, which affect decomposition instead.
21. What is the annual net primary productivity of the biosphere?
(a) 55 billion tons
(b) 170 billion tons
(c) 70 billion tons
(d) 100 billion tons
22. Why is ocean productivity lower despite covering 70% of Earth’s surface?
(a) Lack of sunlight
(b) Limited nutrients
(c) Too many decomposers
(d) Excess water
23. Which organism is referred to as the farmer’s friend due to its role in decomposition?
(a) Bacteria
(b) Earthworm
(c) Fungi
(d) Algae
24. What is the raw material for decomposition?
(a) Living plants
(b) Detritus
(c) Water
(d) Sunlight
25. Which process in decomposition involves breaking detritus into smaller particles?
(a) Leaching
(b) Fragmentation
(c) Catabolism
(d) Mineralisation
26. What happens during the leaching process in decomposition?
(a) Detritus is broken into smaller pieces
(b) Water-soluble nutrients sink into the soil
(c) Organic matter is converted to inorganic substances
(d) Humus is formed
27. Which process involves bacterial and fungal enzymes degrading detritus?
(a) Fragmentation
(b) Leaching
(c) Catabolism
(d) Humification
28. What is humus?
(a) A simple inorganic substance
(b) A dark, amorphous substance resistant to microbial action
(c) Fresh plant material
(d) A type of bacteria
29. What process releases inorganic nutrients from humus?
(a) Fragmentation
(b) Leaching
(c) Mineralisation
(d) Catabolism
30. Which condition slows decomposition?
(a) Warm and moist environment
(b) High nitrogen content
(c) Low temperature and anaerobiosis
(d) High sugar content
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