Final answer:
New species evolve divergently when genes differentiate from a common ancestor, a process called divergent evolution. Allopatric speciation is one way new species arise when populations evolve independently due to geographical separation. These concepts are pivotal in understanding the diversity of life and the evolutionary processes that drive it.
Step-by-step explanation:
Once a species evolves, these new species evolve divergently again as genes differentiate from the common ancestor. This process, known as divergent evolution, results in different forms in two species with a common ancestor. As species disseminate and adapt to various environments, they accumulate genetic differences that lead to diverse traits. New species can arise through methods such as allopatric speciation, where geographical separation causes populations of the same species to evolve independently until they can no longer interbreed and become unique species.
Evolution may also be convergent, with similar traits evolving in multiple species. Regardless of the type of evolution, the source of variation within species is genetic variation, with advantageous traits being selected for survival. Organisms evolve through 'descent with modification' from common ancestors, meaning that while related organisms share characteristics and genetic codes, they also acquire changes through time. This can lead to the formation of new species if separated groups accumulate enough genetic differences through adaptations and mutations.