Final answer:
Migration is an environmental adaptation rather than a genetic mutation, pleiotropy, or phenotypic plasticity. It allows species to survive by relocating to favorable environments and contributes to genetic variation and adaptive evolution through gene flow.
Step-by-step explanation:
Migration is an environmental adaptation that occurs in various species. It is an evolved, adapted response to variation in resources and can greatly affect an organism's survival and reproduction by allowing access to different environments that might be more favorable in different seasons or life cycle stages. In the given example of the Snake Island population, early generations of snakes that migrated improved their survival chances, and this behavior was taught to successive generations, further highlighting migration as an adaptation. Additionally, migration can introduce new genetic variation into a population through gene flow, as immigrant individuals with different alleles may interbreed with the local population, supporting the frequency of those alleles.
Furthermore, when discussing rapid adaptive evolution, evidence shows that certain species can quickly adapt to new environments, as highlighted in the cases of the cane toad and the European crab. The development and successful spread of adaptive traits are often a result of natural or sexual selection, and while mutation can create new traits, it is the migration that spreads those traits through populations, thereby enriching the genetic diversity and potential adaptability of a species.