From Land Animal to King of the Sea
Whales——or their ancestors——were once land animals.Scientists believe that they roamed the earth about 150million years ago.
The landd welling ancestors of this modern king of the sea were hunters with legs and the jaws and teeth of killers.Their favorite hunting grounds were probably shallow waters near the mouths of rivers or off a level stretch of coast, for fish, both finny and shell, were then more plentiful and easier to catch than animals.Because of this, these land mammals came to spend more and more time in the water.
Ages passed, and these creatures swam more easily than they walked；millions of years later they were able to do without legs altogether.They were now recognizable as whales.Their forelegs had turned into the flippers that today's whales use for steering；their hind legs had shrunk so that mere traces of them can be found under the skin when a whale is dissected.
從陸上動物到海中
鯨——或者說鯨的祖先——曾經(jīng)是陸地上的動物?？茖W家們認為，大約在1.5億年以前，它們曾在陸地上轉(zhuǎn)悠。
這個現(xiàn)代海中的陸上祖先，是有腿、有顎、有利齒的獵手。它們最喜歡的狩獵場，是靠近河口或是平坦海岸的近海淺水區(qū)，因為當時有鰭的魚類和貝殼類動物比現(xiàn)在要多，而且比其它動物更容易捕捉。由于這一緣故，這些陸地上的哺乳動物便逐漸在水中呆得越來越長了。
幾千幾萬年過去了，這些動物在水里游起來比在陸地上行走更加悠然自得；幾百萬年以后，它們便壓根兒不需要腿了，這時就可辨認出它們是鯨了。它們的前腿變成鰭狀肢，今天的鯨魚便是用它來掌握方向的；它們的后腿萎縮了，因而只有當鯨魚被解剖時，才能在皮膚下見到后腿的一些痕跡。
Whales——or their ancestors——were once land animals.Scientists believe that they roamed the earth about 150million years ago.
The landd welling ancestors of this modern king of the sea were hunters with legs and the jaws and teeth of killers.Their favorite hunting grounds were probably shallow waters near the mouths of rivers or off a level stretch of coast, for fish, both finny and shell, were then more plentiful and easier to catch than animals.Because of this, these land mammals came to spend more and more time in the water.
Ages passed, and these creatures swam more easily than they walked；millions of years later they were able to do without legs altogether.They were now recognizable as whales.Their forelegs had turned into the flippers that today's whales use for steering；their hind legs had shrunk so that mere traces of them can be found under the skin when a whale is dissected.
從陸上動物到海中
鯨——或者說鯨的祖先——曾經(jīng)是陸地上的動物?？茖W家們認為，大約在1.5億年以前，它們曾在陸地上轉(zhuǎn)悠。
這個現(xiàn)代海中的陸上祖先，是有腿、有顎、有利齒的獵手。它們最喜歡的狩獵場，是靠近河口或是平坦海岸的近海淺水區(qū)，因為當時有鰭的魚類和貝殼類動物比現(xiàn)在要多，而且比其它動物更容易捕捉。由于這一緣故，這些陸地上的哺乳動物便逐漸在水中呆得越來越長了。
幾千幾萬年過去了，這些動物在水里游起來比在陸地上行走更加悠然自得；幾百萬年以后，它們便壓根兒不需要腿了，這時就可辨認出它們是鯨了。它們的前腿變成鰭狀肢，今天的鯨魚便是用它來掌握方向的；它們的后腿萎縮了，因而只有當鯨魚被解剖時，才能在皮膚下見到后腿的一些痕跡。