Species X has lived in the forest for many years. One day, some individuals in the Species X forest population moved to the mountains, away from the native habitat in which they had lived for so long. A large river then developed between the mountains and the forest, separating the two environments. None of the Species X individuals in the forest could travel to the mountains and none in the mountains could come back to the forest. Gradually, over time, the individuals that had moved to the mountains became increasingly different from the animals that remained in the forest. Eventually, the Species X individuals that moved to the mountains became so different from those in the forest that they could no longer breed with one another.

Which of the following best describes this type of speciation?

Which of the following is not an assumption made by Hardy-Weinberg equilibrium?

In which type of speciation does a new species evolve from an ancestral species while inhabiting the same area as the ancestral species?