Which of the following is NOT one of the three postulates of Darwinian evolution?

The correct answer is that hybrid vigor is not one of the three postulates of Darwinian evolution. Darwin's theory is fundamentally built around the concepts of natural selection and adaptation through a specific framework that includes three main postulates: the struggle for existence, variation in fitness, and inheritance of variations.

The struggle for existence refers to the competition among individuals for resources necessary for survival, which drives natural selection. Variation in fitness denotes that individuals exhibit differences in their ability to survive and reproduce based on inherited traits, leading to the notion that certain characteristics can provide advantages in specific environments. Lastly, inheritance of variations highlights that traits passed from parents to offspring can influence evolutionary change over generations.

Hybrid vigor, on the other hand, pertains to the phenomenon where hybrid offspring exhibit superior qualities or traits compared to their parents. It is more related to genetics and breeding than to the core concepts of Darwin's theory of evolution. Thus, while hybrid vigor is a significant concept in genetics, it does not form part of the foundational postulates that explain the mechanisms of evolution as outlined by Darwin.