Geomorphological Origin of World's Freshwater Lakes:
More than $70\%$ of the world's natural freshwater lakes (including the Laurentian Great Lakes of North America and thousands of kettle lakes in Canada, Scandinavia, and Russia) were created by glacial activity during Pleistocene continental glaciations.
Glaciers carved deep rock depressions (cirque and tarn lakes) or dammed drainage channels with glacial terminal moraines.
Correct Option: Option 3 (Glacial).
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22
ICAR JRF Fish Processing Technology 29 Jun 2024Shift 1
MCQ (Single Correct)+4−1
What is the primary function of aerenchyma in aquatic plants?
Aerenchyma: Specialized parenchymatous tissue containing interconnected, continuous longitudinal gas-filled spaces (lacunae) found extensively in roots, stems, and leaves of aquatic macrophytes (hydrophytes like Typha, Phragmites, water hyacinth, and wetland rice).
Primary Function: Provides a low-resistance internal gas-conduction pathway for the convective and diffusive transport of atmospheric oxygen from aerial leaves down to submerged roots and rhizomes embedded in anoxic, waterlogged sediments.
Correct Option: Option 1 (To transport oxygen to roots).
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23
ICAR JRF Fish Processing Technology 29 Jun 2024Shift 1
MCQ (Single Correct)+4−1
What is the main role of macroinvertebrates in assessing water quality in streams and rivers?
Benthic macroinvertebrates (insects like mayflies, stoneflies, caddisflies; mollusks; crustaceans) inhabit the stream bottom sediment and possess varying tolerance thresholds to water pollution, nutrient enrichment, and dissolved oxygen depletion.
Because of their sedentary habits and lifespan of months to years, their community structure, richness, and biotic indices (e.g., EPT Index, BMWP Score) act as sensitive bioindicators (biomonitors) of long-term aquatic environmental health.
Correct Option: Option 4 (Bioindication).
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24
ICAR JRF Fish Processing Technology 29 Jun 2024Shift 1
MCQ (Single Correct)+4−1
The increased performance of HPLC is related to one of the following
In High-Performance Liquid Chromatography (HPLC), the theoretical plate height ($H$) is described by the van Deemter equation:
$$H = A + \frac{B}{u} + C u$$
Reducing the particle size of the stationary phase ($d_p$) from $10\,\mu\text{m}$ to $3-5\,\mu\text{m}$ (or sub-$2\,\mu\text{m}$ in UHPLC) substantially decreases eddy diffusion ($A \propto d_p$) and stationary phase mass transfer resistance ($C \propto d_p^2$).
This drastically reduces band broadening and increases theoretical plate numbers ($N$), resulting in superior chromatographic resolution and performance.
Correct Option: Option 1 (Decreased particle size of the stationary phase).
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25
ICAR JRF Fish Processing Technology 29 Jun 2024Shift 1
MCQ (Single Correct)+4−1
In GCMS, the individual components are separated based on their
In Gas Chromatography-Mass Spectrometry (GC-MS), gaseous compounds separated by the GC capillary column enter the mass spectrometer ion source where they are ionized and fragmented.
The resulting charged molecular ions and fragments are separated and quantified by the mass analyzer (quadrupole, time-of-flight, or ion trap) strictly on the basis of their mass-to-charge ratio ($m/z$).
Correct Option: Option 3 (Mass to charge ratio of the component).
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