Rhizobium bacteria form symbiotic relationships with legume roots, fixing atmospheric nitrogen into ammonia and nitrates usable by plants.
Q.23Medium
Which of the following organisms would show the highest concentration of pesticide residues in an aquatic food chain?
Answer: C
Bioaccumulation and biomagnification increase at higher trophic levels. Top predators accumulate the highest pesticide concentrations.
Q.24Medium
According to the 10% law of energy transfer, if primary producers in an ecosystem contain 10,000 kcal of energy, how much energy would be available to secondary consumers?
Answer: B
Energy transfer: 10,000 kcal (producers) → 1,000 kcal (primary consumers) → 100 kcal (secondary consumers). Each trophic transfer retains ~10%.
Q.25Medium
Which succession type would occur on bare rock in the Western Ghats with no previous soil?
Answer: B
Primary succession occurs on bare substrate with no pre-existing soil. Lichens and mosses are pioneer species.
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Q.26Medium
In India's Western Coastal regions, which of the following represents a keystone species in mangrove ecosystems?
Answer: A
Crabs in mangrove ecosystems regulate sediment composition and nutrient cycling, disproportionately affecting ecosystem structure.
Q.27Medium
Which of the following is NOT a density-dependent factor affecting population growth?
Answer: C
Earthquakes are density-independent factors. Density-dependent factors (competition, parasitism, disease) increase with population density.
Q.28Medium
In the carbon cycle, which process is primarily responsible for returning carbon dioxide to the atmosphere in terrestrial ecosystems?
Answer: D
Both cellular respiration by organisms and decomposition of dead organic matter release CO2 back into the atmosphere.
Q.29Medium
Which mechanism would best explain the survival of antibiotic-resistant bacteria in hospital environments?
Answer: B
Antibiotic-resistant strains survive and proliferate while susceptible strains are eliminated, exemplifying natural selection.
Q.30Medium
In India's Sundarbans, the Bengal tiger population is threatened primarily by habitat loss due to:
Answer: B
Sundarbans face threats from climate change-induced sea level rise and human encroachment, reducing tiger habitat.
Q.31Medium
Which of the following is an example of resource partitioning in nature?
Answer: B
Resource partitioning reduces competition by allowing species to utilize different niches (feeding at different heights).
Q.32Medium
Which of the following best explains the concept of ecological resilience?
Answer: B
Ecological resilience is the capacity to recover from disturbances and return to equilibrium state.
Q.33Medium
In the Western Ghats biodiversity hotspot, what percentage of plant species are endemic to India?
Answer: B
The Western Ghats contains about 60% endemic plant species, making it one of India's most critical biodiversity areas.
Q.34Medium
According to India's National Green Tribunal (NGT) 2024 decisions, which industrial effluent poses the greatest threat to the Yamuna River ecosystem?
Answer: B
Leather tanning wastes contain high concentrations of chromium and other heavy metals that severely degrade aquatic ecosystems.
Q.35Medium
In a forest biome, if 1000 kg of plant biomass is available at the producer level, approximately how much energy would be available at the secondary consumer level (assuming 10% energy transfer)?
Answer: B
Following the 10% law: Producers (1000 kg) → Primary consumers (100 kg) → Secondary consumers (10 kg).
Q.36Medium
In India's coral reef ecosystems, what is the primary cause of coral bleaching observed in the Andaman and Nicobar Islands since 2020?
Answer: B
Elevated sea surface temperatures stress coral-zooxanthellae relationships, causing bleaching. This has been documented extensively in Andaman reefs.
Q.37Medium
Which statement about India's Project Tiger is most accurate?
Answer: B
India's tiger population has shown significant recovery, increasing from approximately 1400 tigers in 2006 to over 3700 by 2023 census.
Q.38Medium
In the bioaccumulation of DDT pesticide in aquatic food chains, which organism typically shows the highest concentration?
Answer: D
Biomagnification causes DDT concentration to increase at higher trophic levels, with apex predators (birds) showing highest concentrations.
Q.39Medium
Which of the following represents a density-dependent factor in the Indian subcontinent ecosystems?
Answer: B
Interspecific competition is density-dependent as its effect increases with population density. Environmental factors like rainfall are density-independent.
Q.40Medium
In India's mangrove ecosystems, which species serves as the keystone species maintaining ecosystem structure?
Answer: B
Rhizophora species form the structural foundation of mangrove ecosystems, providing nursery grounds and stabilizing sediment for other organisms.
