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http://online1.tingclass.net/voaspe/…/20160110sa_science.mp3
🎁 中英文稿:
March 27th, 1964: the world's second-most powerful recorded earthquake hits Alaska.
1964年,3月27日,阿拉斯加發生了世界上第二強大的地震。
"What happened was the whole Gulf of Alaska and Prince William Sound just sort of tilted, and so near shore, near Alaska, that region sank. And then out at sea, the sea floor raised up." Susie Bassham, a molecular biologist at the University of Oregon. "And so things that were submarine platforms before suddenly were lifted above sea level, and then silt could come in and build more island."
“整個阿拉斯加海灣和威廉王子灣發生了傾斜,阿拉斯加附近發生了塌陷。海床升高。”Susie Bassham是俄勒岡州立大學的分子生物學家,她還說到,“海底高地突出海平面,淤泥可以用來建立更多的島嶼。”
And with more island, came new freshwater ponds. Those newly created bodies of water turned out to be the testbed for a natural evolutionary experiment on a finger-sized fish, called the three-spined stickleback. Saltwater fish went in… freshwater fish came out. "Big silvery well-armored fish entered freshwater ponds. And during the last 50 years they changed their size, their coloration, they changed the size of their eyes, the length of their spines, many aspects of their skeletons, feeding structures, swimming structures, and became more stereotypical freshwater fish." But how?
島嶼更多,就會有新的淡水池塘。原來這些新的淡水池塘是用來對一種手指大小的魚——三刺魚——進行自然進化實驗的。這種鹹水魚潛入水底,然後出來的就是淡水魚。“這種大銀灰色刺魚,進入淡水池塘。在過去的50年,它們的體型、顏色發生了變化。同時眼睛的大小、棘突長度、骨骼的很多方面、進食和游泳結構都發生了變化,越來越像淡水魚。”但是這是怎麼發生的呢?
Bassham and her colleagues ran statistical analyses on the genomes and body measurements of fish living in those freshwater ponds today. And they found that the saltwater versions of the fish may have actually colonized those freshwater ponds on the study islands at least six times in the last 50 years. They were able to move in and rapidly adapt because the sea-dwelling fish have a sort of "sleeper genome" of freshwater traits, just waiting to be activated.
Bassham和同事們對淡水池塘的魚進行了基因組和身體測量。研究發現,這些鹹魚版的淡水魚在實驗島嶼的淡水池塘至少生活了50年。這中深海魚,能夠快速的適應淡水環境,因為它們具有淡水魚的“休眠基因”。這些基因只是在等待被啟動。
"These are anadromous fish that have been invading freshwater ecosystems over and over and over. And all those freshwater adaptations have trickled back into the sea, allowing the oceanic population, which is believed to be the ancestor of all the freshwater populations, to maintain this huge resource of differently, alternately adapted genotypes that are just waiting to get back into a freshwater system."
這些溯河性魚類在一次又一次的入侵淡水魚生態系統。這些慢慢適應淡水的鹹水魚,回流到大海裡,這可以讓鹹水魚種類多樣化——人們認為鹹水魚是淡水魚的祖先——之後,已經適應大海的鹹水魚再回到淡水系統。