Question

____________________-dependent selection is another mechanism of balancing selection. In this pattern of natural selection, the fitness of a genotype decreases when its frequency becomes higher. In other words, rare individuals have a higher fitness than more common individuals.

Answer 1

Negative frequency-dependent selection increases a population's genetic diversity by favoring rare phenotypes, while positive frequency-dependent selection does the opposite by favoring common phenotypes. An observed example is the mating strategies of side-blotched lizards, which maintain population diversity through a rock-paper-scissors dynamic.

Step-by-step explanation:

Negative Frequency-Dependent Selection

Negative frequency-dependent selection is a form of natural selection where the fitness of a phenotype decreases as it becomes more common in the population. Conversely, rare phenotypes have increased fitness. This mechanism promotes genetic diversity by giving an advantage to less common phenotypes within a population. An example of negative frequency-dependent selection is observed in male side-blotched lizards (Uta stansburiana) where three different throat-colored morphs (orange, blue, and yellow), each with varying strategies for reproduction, interact dynamically in a way that resembles the game of rock-paper-scissors.

Positive frequency-dependent selection, on the other hand, enhances the fitness of more common phenotypes and tends to decrease genetic diversity. Sexual selection can result in sexual dimorphisms, where males and females present different attributes due to different selective pressures on reproductive success.