Final answer:
The Red Queen hypothesis posits that sexual reproduction is essential for species to survive in an ever-evolving environment, particularly against parasites.
Step-by-step explanation:
The Red Queen hypothesis suggests that sexual reproduction allows organisms to enhance their survival by maintaining or improving their fitness in a continuously evolving environment. This coevolutionary process involves species adapting and re-adapting in response to evolutionary changes in other species, such as predators, prey, and especially parasites. The best scenario that supports the Red Queen hypothesis from the given choices would be:
b. Individuals of a snail population that reproduce asexually die out after a parasite invades its territory.
This example illustrates how the lack of genetic variation in asexual reproduction can lead to a population's decline when faced with the evolutionary adaptations of parasites. The genetic variation produced by sexual reproduction is crucial for populations to adapt and survive in the face of such challenges, embodying the "running to stay in the same place" analogy of the Red Queen hypothesis.