The old horse crouches, aiming at thousands of miles; Martyrs are full of courage in their twilight years. -Cao Cao.

A man should study. Black hair doesn't know how to study hard early, but regrets it later. -Yan Zhenqing

Animal taxonomists classify animals according to their various characteristics (morphology, cell, heredity, physiology, ecology and geographical distribution, etc.). ) and divide it into six main grades, namely, phylum, class, order, family, genus and species.