How does an embryo differ from a fetus?

The distinction between an embryo and a fetus is primarily based on developmental stages. The correct choice highlights that a fetus has essential structures formed, which is accurate because the fetal stage marks a significant point in prenatal development where major organs and systems begin to mature and take on their more recognizable forms.

During the embryonic stage, which lasts from conception until about eight weeks, the developing organism is called an embryo. In this phase, cells rapidly divide and differentiate, leading to the formation of foundational structures such as the heart and neural tube. By the time the organism transitions to the fetal stage, important bodily structures are already in place and further development focuses on growth and refinement rather than the initial formation of organs.

In contrast, while an embryo is indeed a collection of cells at the early stage of development, it is not limited to just one cell after the first few days post-fertilization. The option discussing the embryo's origin is misleading, as both the embryo and fetus develop from the fertilized egg, but the organ structures become more pronounced once the embryo develops into a fetus. Lastly, the assertion that a fetus has yet to develop any cells is incorrect because the fetal stage follows the extensive cellular development that occurs during the embryonic stage, making it clear