Answer:
When a species branches off from the main line, it undergoes speciation. Speciation is the evolutionary process by which populations of a single species diverge and become two or more separate species over time. This can occur due to a variety of factors, such as geographic isolation, genetic mutations, natural selection, and genetic drift. The resulting populations can accumulate enough differences in genetic and phenotypic traits to become reproductively isolated from each other, meaning they can no longer interbreed and produce viable offspring. This marks the emergence of a new species.
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