The process by which nitrogen is converted from atmospheric N₂ to usable forms by microorganisms is called:
Answer: B
Nitrogen fixation is the conversion of atmospheric N₂ to ammonia (NH₃) or nitrates by nitrogen-fixing bacteria like Rhizobium and Azospirillum.
Q.202Medium
Which of the following best describes 'eutrophication'?
Answer: B
Eutrophication is the over-enrichment of water with nutrients (phosphates and nitrates), leading to excessive algal growth, dead zones, and oxygen depletion.
Q.203Medium
Which of the following is a density-independent factor affecting population dynamics?
Answer: C
Drought is a density-independent (abiotic) factor because its effect on population is not influenced by population density. It equally affects all populations regardless of density.
Q.204Medium
A forest ecosystem in the Western Ghats shows a decline in apex predator population, leading to an increase in herbivore numbers and subsequent overgrazing. Which ecological principle is being violated in this scenario?
Answer: D
The carrying capacity of the ecosystem is being exceeded due to removal of natural predators. Herbivore populations exceed the ecosystem's ability to sustain them without degradation, violating the carrying capacity principle. This leads to overgrazing and ecosystem destabilization.
Q.205Medium
Which of the following crops is NOT approved for cultivation as Bt transgenic in India?
Answer: D
As of 2024-25, only Bt Cotton is commercially cultivated in India. Bt Brinjal has regulatory issues, and Bt Rice/Maize are not approved yet.
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Q.206Medium
Which method of plant genetic engineering does not require a vector?
Answer: D
Both microprojectile bombardment (gene gun) and electroporation are direct DNA delivery methods that don't require a biological vector.
Q.207Medium
Golden Rice is transgenic rice enriched with which nutrient?
Answer: C
Golden Rice contains genes for beta-carotene production, making it rich in Vitamin A, addressing nutritional deficiency in rice-consuming populations.
Q.208Medium
What is the primary purpose of callus tissue in plant biotechnology?
Answer: B
Callus is undifferentiated plant tissue used in micropropagation and plant regeneration through somatic embryogenesis or organogenesis.
Q.209Medium
Which hormone ratio favors shoot formation in plant tissue culture?
Answer: B
A low auxin to high cytokinin ratio promotes shoot formation, while the opposite (high auxin : low cytokinin) promotes root formation.
Q.210Medium
Which of the following is a somaclone?
Answer: B
Somaclones are plants regenerated from somatic cells via tissue culture, genetically identical to the parent plant unless mutations occur.
Q.211Medium
What is the significance of the T-DNA in Agrobacterium tumefaciens?
Answer: B
T-DNA (Transfer DNA) is the specific segment of the Ti plasmid that integrates into the plant genome during Agrobacterium-mediated transformation.
Q.212Medium
What is a marker-assisted selection (MAS) in plant breeding?
Answer: B
MAS uses molecular markers (DNA sequences) to identify and select plants carrying desired genes without waiting for phenotypic expression.
Q.213Medium
Which regulatory body in India approves genetically modified crops?
Answer: B
The GEAC under the Ministry of Environment, Forest and Climate Change approves GM crops in India after safety and efficacy assessment.
Q.214Medium
Bt cotton produces Cry1Ac protein that is toxic to lepidopteran insects. Which of the following statements correctly describes the mechanism of toxin action?
Answer: A
Cry proteins from Bacillus thuringiensis work by binding to specific receptors in the alkaline midgut of susceptible insects, forming pores that lead to cell lysis and death. This is the well-established mechanism of Bt toxin action, making it selective for certain insect orders.
