Final answer:
Sex has an adaptive significance in biology as it generates variation in populations, providing the basis for natural selection and the evolution of species.
Step-by-step explanation:
In biology, sex has an adaptive significance because it generates variation within a population, which is important for the process of evolution. Variation provides the 'raw material' upon which natural selection can act. Sex also plays a role in the concept of species, as interbreeding is necessary for populations to be grouped together as a species. While sex can be complicated, costly, and even dangerous, its adaptive significance lies in promoting genetic diversity and allowing for evolutionary processes to occur.