USA Biology Olympiad (USABO) Practice Exam

In most terrestrial mammalian species, which statement is true regarding parental investment?

1. Males invest more than females.

2. Females and males invest equally.

3. Females are typically 'K-selected', whereas males are 'r-selected'.

4. Only males exhibit parental investment.

The correct answer is: Females are typically 'K-selected', whereas males are 'r-selected'.

In most terrestrial mammalian species, the concept that females are typically 'K-selected' while males display 'r-selected' traits is rooted in the theories of reproductive strategies. K-selection is characterized by producing fewer offspring with higher parental care and investment to ensure those offspring survive to adulthood. Females, investing significant time and resources into gestation and nurturing, often embody this K-selected strategy. In contrast, r-selection is associated with producing a large number of offspring with minimal investment, relying on the sheer number to increase the chances that some will survive. Males, in many species, may exhibit this r-selected behavior by investing less in individual offspring, focusing instead on mating with multiple females to maximize their reproductive success. This understanding aligns with observed parental behaviors in many mammalian species, where maternal investment tends to be significantly higher due to the biological and energetic demands of reproduction and nurturing, while male investment can vary widely and is often lower. Thus, the statement regarding the parental investment traits of females and males accurately reflects these ecological and evolutionary dynamics.