Ecosystem structures can be understood through functional interactions. Identify the correct statements regarding functional aspects of ecosystems:
I. The components of an ecosystem operate as a unit when we consider productivity, decomposition, energy flow, and nutrient cycling. II. Inorganic nutrients enter the biotic component through decomposers. III. Energy flow is cyclic, while nutrient flow is unidirectional. IV. Autotrophs serve as the primary link converting abiotic elements into organic components using solar energy.
Statements I and IV are correct. Statement II is incorrect because inorganic nutrients enter the biotic component through producers, while decomposers return nutrients to the soil. Statement III is incorrect because energy flow is unidirectional whereas nutrient flow is cyclic.
Question 42 of 100
📘 CLASS XII
In a pond ecosystem, different structural elements have different functional roles. Which of the following is/are correct?
I. Water acts as the medium for abiotic dissolved nutrients. II. Phytoplankton acts as the primary producer. III. Fungi act as primary consumers. IV. Zooplankton acts as primary consumers.
Statements I, II, and IV are correct. Statement III is incorrect because fungi are decomposers (saprotrophs), not primary consumers.
Question 43 of 100
📘 CLASS XII
The photosynthetic efficiency of plants on a global scale is surprisingly restricted. Study these statements:
I. Of the total incident solar radiation, less than 50% is photosynthetically active radiation (PAR). II. Plants capture only 2-10% of the PAR. III. Net primary productivity is GPP minus respiratory losses. IV. On a global scale, plants convert nearly 10% of total incident solar radiation into biomass.
Statements I, II, and III are correct. Statement IV is incorrect because the conversion efficiency of total incident solar radiation into biomass is far below 1%.
Question 44 of 100
📘 CLASS XII
Detritus degradation rate depends on specific biological features of the soil fauna. Read the statements below:
I. Fragmentation is carried out by detritivores like earthworms. II. Catabolism is carried out by water-soluble nutrients leaking into the soil. III. Bacterial and fungal enzymes carry out catabolism. IV. Leaching is the process of movement of water-soluble inorganic nutrients down into the soil.
Statements I, III, and IV are correct. Statement II is incorrect because catabolism is the enzymatic breakdown of detritus by bacteria and fungi, whereas leaching is the downward movement of soluble nutrients.
Question 45 of 100
📘 CLASS XII
Food chains show different lengths depending on trophic stability. Consider these statements:
I. The grazing food chain is always longer than the detritus food chain. II. The number of trophic levels in a GFC is restricted by the 10% energy transfer law. III. In nature, a GFC of more than 4 to 5 trophic levels is highly rare. IV. Detritus food chain contains no trophic levels because decomposers eat everything simultaneously.
Statements II and III are correct. Statement I is incorrect because grazing food chains are not necessarily longer than detritus food chains. Statement IV is incorrect because detritus food chains also possess distinct trophic levels.
Question 46 of 100
📘 CLASS XII
The nature of pioneer species in primary succession is highly habitat-dependent. Analyze these pairs:
I. Primary succession on bare rock → Lichens II. Primary succession in water → Phytoplanktons III. Secondary succession on burned forest → Large forest trees directly IV. Primary succession on sand dunes → Submerged rooted plants
Statements I and II are correct NCERT pioneer matches. Statement III is incorrect because secondary succession starts with grasses and herbs, not large trees directly. Statement IV is incorrect because sand dunes are dry xerophytic habitats where submerged aquatic plants cannot act as pioneer species.
Question 47 of 100
📘 CLASS XII
Seral communities change the abiotic environment during succession. Consider these developmental feedback concepts:
I. As succession proceeds, the number of species increases. II. As succession proceeds, total biomass increases. III. Seral communities modify the physical environment, making it less favorable for themselves and more favorable for new species. IV. A stable climax community continues to modify its habitat rapidly, making it unstable.
Statements I, II, and III are correct developmental traits of succession. Statement IV is incorrect because a climax community remains in equilibrium with the environment and is relatively stable.
Question 48 of 100
📘 CLASS XII
The global nitrogen cycle differs fundamentally from the global phosphorus cycle. Study the comparison below:
I. Nitrogen cycle is gaseous, whereas phosphorus cycle is sedimentary. II. Nitrogen is fixed by biological nitrogen fixers, whereas phosphorus is released primarily by weathering of rocks. III. Nitrogen cycle has no atmospheric pool, while phosphorus cycle has a massive atmospheric reservoir. IV. Both cycles rely heavily on plant roots for absorption.
Statements I, II, and IV are correct. Statement III is incorrect because the nitrogen cycle has a large atmospheric reservoir, whereas the phosphorus cycle has no significant atmospheric reservoir.
Question 49 of 100
📘 CLASS XII
Consider the carbon cycle interactions between oceans and the atmosphere:
I. Ocean water absorbs carbon dioxide from the atmosphere. II. Atmospheric carbon dioxide dissolves in oceans as carbonates and bicarbonates. III. Oceanic carbon is completely isolated from the terrestrial carbon cycle. IV. Human fossil fuel burning has no impact on oceanic carbon levels.
Statements I and II are correct. Statement III is incorrect because oceanic and terrestrial carbon cycles are interconnected through atmospheric CO2 exchange. Statement IV is incorrect because fossil fuel burning increases atmospheric CO2, increasing oceanic absorption and contributing to ocean acidification.
Question 50 of 100
📘 CLASS XII
Trophic level assignments can be complex. Analyze the statements regarding food web positions:
I. A consumer that feeds on primary consumers is a secondary consumer. II. A single species can occupy different trophic levels simultaneously. III. A sparrow eating seeds is a primary consumer, while eating caterpillars is a secondary consumer. IV. Human beings are always primary consumers because we are omnivores.
Statements I, II, and III are correct NCERT concepts. Statement IV is incorrect because humans may function as primary, secondary, or tertiary consumers depending on their diet.
