Population, Quantitative & Conservation Genet

• Mechanism of Biological Evolution by Natural Selection:
• Natural selection operates across hierarchical levels of biological organization:

• Genes mutate: Random DNA mutations create novel genetic variation.
• Individuals are selected: Differential survival and reproductive fitness act on individual phenotypes.
• Populations evolve: Allele and genotype frequencies shift collectively over generations within the breeding population.
  • Correct Option: Option 4 (mutate; are selected; evolve).

• Feeding Strategies and Ecology of Fishes:
• Necrophagous fish are carrion-eaters: True. Scavenging fishes (e.g., hagfish) feed on dead decaying animal carcasses.
• Polyphagy predominates in boreal and arctic zones: True. In high-latitude cold environments with short seasonal resource pulses, generalist feeding (polyphagy / opportunism) is favored over narrow specialization.
• Ambush predators actively search and pursue prey: False. Ambush predators (e.g., anglerfish, stonefish, pike) remain motionless, camouflaged, waiting to strike passing prey rather than actively chasing.
• Temporal aphagy is typical in anadromous fish during spawning: True. Anadromous fishes (e.g., salmonids, Tenualosa ilisha) cease feeding entirely (aphagy) during upstream freshwater reproductive migrations, catabolizing stored lipids and proteins.
• Statements (A), (B), and (D) are correct.
• Correct Option: Option 1 ((A), (B) and (D) only).

• Assumptions of Hardy-Weinberg Equilibrium (HWE):
• HWE states that allele and genotype frequencies remain constant across generations in the absence of evolutionary forces: large population size (no drift), random mating, no mutation, no natural selection, and no migration (gene flow).
• Effect of Migration:
• Migration involves the movement of breeding individuals (and their gametes) into or out of a population.
• Immigration introduces new alleles or changes existing allele frequencies according to:

where $m$ is the migration rate and $p_m$ is immigrant allele frequency.

• Consequently, migration directly disrupts Hardy-Weinberg equilibrium.
• nalysis:
• (It disrupts the equilibrium by introducing new alleles): Correct.

Correct option: (4) It disrupts the equilibrium by introducing new alleles