The following table lists selected concepts (Column X) in behavioral biology and their descriptions (Column Y):

Column X	Column Y
A. Allee effect	i. Male–male interactions increase plasma testosterone and thus sustain subsequent aggressive behaviour
B. Bateman’s hypothesis	ii. Parasites and pathogens play an important role in sexual selection when secondary sexual traits are costly and condition-dependent.
C. Challenge hypothesis	iii. A situation in which the fitness of individuals increases with increased population density.
D. Hamilton-Zuk hypothesis	iv. Female reproductive success is most strongly limited by the number and success of eggs that she can produce, while male reproductive success is limited by the number of matings he has.

Which one of the following options represents the correct match between Column X and Column Y?

Correct option is D

The Correct Answer is 4  - A–iii, B–iv, C–i, D–ii

Explanation:

Let’s match each concept in Column X with its accurate description from Column Y:

• A. Allee effect → iii
  The Allee effect explains that individual fitness (survival or reproductive success) increases with population density, especially at low densities. It is important in population dynamics and conservation biology.

• B. Bateman’s hypothesis → iv
  This hypothesis posits that female reproductive success depends on the number of eggs, whereas male reproductive success is driven by the number of matings. It underpins theories of sexual selection.

• C. Challenge hypothesis → i
  The Challenge hypothesis suggests that male–male interactions elevate testosterone levels, which then fuel aggressive and competitive behaviour during the breeding season.

• D. Hamilton-Zuk hypothesis → ii
  This hypothesis suggests that secondary sexual traits indicate resistance to parasites/pathogens, and hence play a critical role in mate selection under sexual selection.

Information Booster:

• Allee effect is critical in understanding extinction thresholds and minimum viable populations.

• Bateman’s hypothesis was foundational in developing Trivers’ parental investment theory.

• Challenge hypothesis explains seasonal hormonal changes, especially in territorial and breeding behavior.

• Hamilton-Zuk hypothesis links host–parasite coevolution with sexual ornamentation.

• These hypotheses guide research in evolutionary ecology, reproductive biology, and ethology.

• They explain how selection pressures shape mating systems and behavior across taxa.