In the animal kingdom, which is broadly divided into the vertebrates and invertebrates, the few vertebrate orders of the birds, mammals, reptiles and amphibians are just a minority.
在被大分為脊椎與無脊椎的動物世界，鳥類、哺乳類、爬蟲、兩棲類等幾個脊椎動物大類雖是少數民族，卻一直是人們探索最多的物種。