What stage of development is characterized by the formation of basic structures in an organism?

The stage of development characterized by the formation of basic structures in an organism is the embryo stage. During this period, which occurs after fertilization and continues until the end of the eighth week of gestation in humans, major systems and structures of the organism are established. This includes the development of the heart, brain, limbs, and other vital organs. The embryo undergoes significant cellular differentiation and morphogenesis, where cells begin to take on specific functions and organize into tissues and organs.

In contrast, the fetus stage follows the embryonic stage, where the primary structures are already formed, and the focus shifts to growth and maturation of those structures. The neonate stage refers to the period immediately after birth, where an organism begins to adapt to life outside the womb. The adult stage is characterized by full development and the ability to reproduce, rather than structural formation. Understanding these stages helps clarify the unique processes and milestones in development.