题目

A group of swans(天鹅) flew down to a beach where a crow was jumping around . The crow(乌鸦) watched them with disdain (鄙视). “You have no flying skills at all!” he said to the swans. “All you can do is to move your wings. Can you turn over in the air? No, that’s beyond you. Let’s have a flying competition. I’ll show you what real flying is! ” One of the swans, a strong young male, took up the challenge. The crow flew up and began to show his skills. He flew in circles, performed other flying tricks, and then came down and looked proudly at the swan. Now it was the下图表示人的个体发育过程。请据图回答：（1）丁由甲细胞发育而来。则甲细胞的名称是 。（2）由乙形成丙，细胞需要经过分裂、 和 的变化。（3）丁要完成一系列复杂的生命活动，需要在 和 的调节下实现