Answer the following questions in about 150 words each:

(a) Define species and explain how paleontological species are different from biological species. (10 marks)

(b) Discuss the geological parameters used to subdivide the Dharwar Craton into two

Question

Answer the following questions in about 150 words each:

(a) Define species and explain how paleontological species are different from biological species. (10 marks)

(b) Discuss the geological parameters used to subdivide the Dharwar Craton into two subcratons. (10 marks)

(c) Describe the Cretaceous volcanic province in India. (10 marks)

(d) Describe how Darcy's law and Reynolds' number are related to the types of fluid flow in aquifers. (10 marks)

(e) Describe the rehabilitation measures required in landslide-affected area to restore the community and the ecology of the area affected. (10 marks)

UPSC Answer Check · Accepted Answer

Species and paleospecies. A species is a basic unit of biological classification; in Mayr's biological species concept, it is a group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups. This definition depends on living organisms, gene flow, and observable reproductive barriers. Paleontological species are inferred from fossils, where interbreeding cannot be tested directly. They are therefore usually defined as morphospecies, based on consistent anatomical, shell, tooth, or skeletal differences, and as chronospecies when a lineage changes through time. The temporal dimension is central: a paleospecies is a name given to a fossil form within a defined stratigraphic interval, and its boundaries may be revised as new fossils appear. This distinction is important in fossil records where only hard parts are preserved. Thus, biological species stress reproductive isolation among living populations, while paleontological species stress morphology, ancestry, and time, with less certainty about gene flow.

Dharwar subcratons. The Dharwar Craton is subdivided into Western and Eastern Dharwar Craton using structural, lithological, and geochronological parameters. The Western Dharwar Craton is dominated by older 3.0–3.4 Ga tonalite–trondhjemite–granodiorite gneisses, with associated greenstone belts that are largely E–W trending. It represents an older crustal block with strong E–W lineations and fold axes. The Eastern Dharwar Craton is characterised by younger 2.5–2.7 Ga juvenile crust, with N–S trending structures and a different lithological assemblage. The Kolar schist belt lies in this eastern part and records later deformation and metamorphism. The contrast in age, trend, and rock type shows that the two subcratons are not merely regional variations but distinct crustal domains separated by a major structural boundary. In practice, the boundary is traced where the E–W greenstone trend changes to N–S, and where zircon ages shift from older TTG to younger granitoid ages. These parameters are used together in mapping.

Cretaceous volcanic province. The Cretaceous volcanic province in India is the Deccan Traps, a large flood-basalt province developed near the Cretaceous–Paleogene boundary, about 67–64 Ma. It covers much of the Deccan Syneclise in peninsular India and is petrologically dominated by tholeiitic basalts. The stratigraphy is commonly divided into three subgroups: the Lower Kalsubai subgroup, the Middle Lonavala subgroup, and the Upper Wai subgroup. These subgroups show variations in lava thickness, flow type, and minor volcanic units, but together form a thick sequence of stacked basalt flows. The three subgroups are described from their vertical succession and lithological changes. The province is linked to the Rajmahal and Sylhet traps, which are considered coeval or related flood-basalt occurrences separated by later rifting and seafloor spreading. The Deccan Traps are therefore described as a major Cretaceous–Paleogene volcanic province with broad areal extent, tholeiitic composition, and a threefold stratigraphic subdivision.

Darcy's law and Reynolds' number. Darcy's law describes laminar flow of water through porous media. It is written as v = -K/μ × dh/dl, where v is flow velocity, K is permeability, μ is fluid viscosity, and dh/dl is the hydraulic gradient. The negative sign shows that flow is from higher to lower hydraulic head. In aquifers, Darcy's law is useful because groundwater usually moves slowly through pore spaces, so the flow is laminar and proportional to the head difference. Reynolds' number, Re = ρvd/μ, is used to test whether that assumption is valid. It compares inertial forces to viscous forces, using fluid density ρ, characteristic velocity v, particle or pore diameter d, and viscosity μ. In groundwater flow, laminar conditions are generally maintained when Re is below the critical range of about 1–10. Above this range, flow may become transitional or turbulent, and Darcy's linear relation may no longer describe the aquifer accurately.

Landslide rehabilitation. Rehabilitation of a landslide-affected area is described in stages that restore both the community and the ecology. Structural measures are used first to stabilise the slope: retaining walls, check dams, drainage channels, slope grading, and anchoring reduce pore pressure and prevent further movement. Bioengineering measures are then applied to bind the soil and rebuild vegetation, using vetiver grass, shrubs, and native afforestation suited to the local slope and rainfall. In Western Ghats or Himalayan cases, these measures are combined with terracing, plantation of native species, and protection of residual soil. Community restoration includes safe resettlement, access roads, water supply, livelihood support, and early warning systems so that people can return or relocate safely. Ecological restoration is completed by re-establishing native plant cover, protecting water sources, and monitoring slope stability and vegetation recovery over time. The sequence is described as emergency stabilisation, slope treatment, community restoration, and ecological recovery.

Answer the following questions in about 150 words each: (a) Define species and explain how paleontological species are different…

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