What is the process by which new species form called?

The process by which new species form is known as speciation. This term specifically refers to the evolutionary process through which populations evolve to become distinct species. Speciation can occur through various mechanisms, such as allopatric speciation, where populations are geographically isolated, or sympatric speciation, which occurs without physical barriers due to factors like behavioral differences or polyploidy in plants.

Understanding speciation is crucial in the study of evolutionary biology, as it explains the diversity of life on Earth and how organisms adapt to their environments over long periods. This process contributes to the creation of the biological diversity we observe today, shaping ecosystems and influencing the ecological roles of different species.

The other options do not pertain to the formation of new species. For instance, the term "spermatid" refers to an immature male gamete, while "species" is a classification that identifies a group of similar organisms. "Solvation" relates to the process of solvent molecules surrounding solute particles, which is not relevant to biological speciation. Thus, speciation stands out as the correct term for the process of forming new species.