Takahashi Kenichi
Osaka Prefecture College of Health Sciences.
Clin Calcium. 2004 Dec;14(12):100-4.
Since primary life appeared in the sea about 3.8 billion years ago, the Agnatha improved a part of the respiratory organ, or brachial arch into the jaw during the evolutionary process. The resulting Gnathostomata could catch bigger fish by using the strong jaw. In addition, they developed specific sensory organs in the head, including nose, eyes and ears for detecting position of diets, brain for treating the sensory information, and muscles for masticating foods. Such development of jaw from the brachial arch had an important meaning in the evolutional history of organisms.
自约38亿年前原生生命出现在海洋中以来，无颌类在进化过程中将其呼吸器官的一部分，即鳃弓，进化成了颌。由此产生的有颌类能够利用强壮的颌捕捉更大的鱼。此外，它们在头部发育出了特定的感觉器官，包括用于探测食物位置的鼻子、眼睛和耳朵，用于处理感觉信息的大脑，以及用于咀嚼食物的肌肉。鳃弓向颌的这种进化在生物进化史上具有重要意义。
