In protostomes, where does the blastopore develop first?

In protostomes, the key characteristic is that the blastopore develops into the mouth. This developmental pathway is distinct from that of deuterostomes, where the blastopore typically becomes the anus. When the zygote divides and undergoes cleavage, the formation of the blastopore marks an important step in the embryonic development of protostomes.

During this process, the mouth forms directly from the blastopore, leading to the overall body plan of these organisms. For example, many animals classified under protostomes, such as arthropods and annelids, share this common developmental trait. The development process is crucial in defining the embryonic structure, influencing the organism's developmental trajectory, and ultimately determining its anatomy and function. Understanding this distinction is vital when studying animal embryology and evolutionary biology.