We shall appreciate this difficulty more clearly, by looking to certain existing faunas and floras.
通过观察某些现存的动物群和植物群,我们就能更清楚地了解这种困难了.
Brackish waters generally support only a small range of faunas.
咸水水域通常只能存活为数不多的几种动物。
Most deep - sea faunas rely for food on particulate matter , ultimately derived from photosynthesis, falling from above.
大多数 深海 动物以上方落下的颗粒物质为食, 这些物质基本上都是通过光合作用形成的.