UPSC Geoscientist Archives

41. Chemoautotrophs are those organisms which obtain energy:

Chemoautotrophs are those organisms which obtain energy:

from the oxidation of organic electron donors in the presence of light.

solely from the oxidation of inorganic electron donors in the presence of light.

from the oxidation of organic electron donors in the absence of light.

solely from the oxidation of inorganic electron donors in the absence of light.

This question was previously asked in

UPSC Geoscientist – 2020

Download PDF Attempt Online

Chemoautotrophs are organisms that obtain energy from chemical reactions, specifically the oxidation of inorganic substances. They do not rely on light for energy.

Chemoautotrophs are distinct from photoautotrophs (which use light energy) and obtain energy from inorganic chemical bonds without requiring light.

Examples of chemoautotrophs include certain bacteria and archaea found in environments like deep-sea hydrothermal vents, sulfur-rich springs, or soil, where they oxidize compounds like hydrogen sulfide, methane, or ferrous iron. They use this energy to synthesize organic compounds from carbon dioxide.

42. Chemosynthetic bacteria found near sub-marine volcanic vents feed on:

Chemosynthetic bacteria found near sub-marine volcanic vents feed on:

Hydrogen sulphide (H₂S).

Organic matter.

Deep sea tube worms.

Inorganic carbon.

This question was previously asked in

UPSC Geoscientist – 2020

Download PDF Attempt Online

Chemosynthetic bacteria found near sub-marine volcanic vents feed on Hydrogen sulphide (H₂S).

Deep-sea hydrothermal vents release various chemicals, including high concentrations of hydrogen sulfide (H₂S). Chemosynthetic bacteria utilize the energy released from the oxidation of H₂S and other reduced inorganic compounds to synthesize organic molecules, forming the base of the food web in these aphotic environments.

Unlike photosynthesis which uses sunlight, chemosynthesis uses chemical energy. The ecosystem around hydrothermal vents is one of the most well-known examples of a chemosynthesis-based ecosystem.

43. Gause`s competitive exclusion principle states that two species:

Gause`s competitive exclusion principle states that two species:

can coexist if they occupy the same niche.

cannot coexist if they occupy the same niche.

cannot coexist if they occupy the adjacent niches.

can coexist if they occupy similar niches.

This question was previously asked in

UPSC Geoscientist – 2020

Download PDF Attempt Online

Gause’s competitive exclusion principle states that two species cannot coexist if they occupy the same niche.

Also known as the principle of competitive exclusion, it posits that if two species compete for the identical set of resources (occupy the same niche), one will inevitably outcompete the other, leading to the local extinction of the less competitive species.

This principle highlights the importance of niche differentiation for the stable coexistence of competing species in an ecological community. Species that coexist typically do so by utilizing different resources or occupying different microhabitats.

44. The incident solar radiation is trapped by constituents of the atmosph

The incident solar radiation is trapped by constituents of the atmosphere and reflect it partly towards the Earth as

microwaves

thermal infrared rays

ultraviolet rays

shortwave radiation

This question was previously asked in

UPSC Geoscientist – 2022

Download PDF Attempt Online

The Earth absorbs incoming shortwave solar radiation and re-emits it as longwave radiation, primarily in the form of thermal infrared rays. Certain atmospheric constituents, known as greenhouse gases, absorb this outgoing infrared radiation and re-emit it in all directions, including back towards the Earth’s surface. This re-emitted radiation is thermal infrared.

– Incoming solar radiation is mostly shortwave (visible, UV, near-IR).
– Outgoing Earth radiation is mostly longwave (thermal infrared).
– Greenhouse gases absorb longwave radiation.
– The greenhouse effect involves the re-emission of absorbed longwave radiation back towards the surface.

Microwaves have longer wavelengths than infrared. Ultraviolet rays are part of the incoming solar radiation spectrum. Shortwave radiation refers generally to incoming solar energy. The trapped and re-directed energy from the atmosphere to the surface is specifically in the thermal infrared range.