In the oysters were raised in much the same way as dirt farmers raised tomatoes- by transplanting them. First, farmers selected the oyster bed, cleared the bottom of old shells and other debris, then scattered clean shells about. Next, they xxxplantedxxx fertilized oyster eggs, which within two or three weeks hatched into larvae. The larvae drifted until they attached themselves to the clean shells on the bottom.
There they remained and in time grew into baby oysters called seed or spat. The spat grew larger by drawing in seawater from which they derived microscopic particles of food. Before long, farmers gathered the baby oysters, transplanted them once more into another body of water to fatten them up. Until recently the supply of wild oysters and those crudely farmed were more than enough to satisfy people‘s needs. But today the delectable seafood is no longer available in abundance. The problem has become so serious that some oyster beds have vanished entirely. Fortunately, as far back as the early 1900‘s marine biologists realized that if new measures were not taken, oysters would become extinct or at best a luxury food. So they set up well-equipped hatcheries and went to work. But they did not have the proper equipment or the skill to handle the eggs. They did not know when, what, and how to feed the larvae. And they knew little about the predators that attack and eat baby oysters by the millions.
They failed, but they doggedly kept at it. Finally, in the 1940‘s a significant breakthrough was made. The marine biologists discovered that by raising the temperature of the water, they could induce oysters to spawn not only in the summer but also in the fall, winter, and spring. Later they developed a technique for feeding the larvae and rearing them to spat. Going still further, they succeeded in breeding new strains that were resistant to diseases, grew faster and larger, and flourished in water of different salinities and temperatures. In addition, the cultivated oysters tasted better!
从历年高考写作题来看, 特别是基础写作, 要点都是一目了然的, 写什么, 对于考生来说不是问题, 问题是不知如何写。实践证明, 只有写出正确地道的句子, 才有可能把文章写好。磨刀不误砍柴功, 写作需练基本功。...
在高中英语实际教学中,包含听、说、读、写等几个主要的方面,任何一个环节都不能松懈,都要保持相对平衡,因为衡量英语学习的重点是学生的综合能力,并不是某一方面的强调。...
写好句子的方法二：改写句子1) Mr. Green is a tall man, who wears a pair of thick glasses. (改成介词短语做伴随状语)1) The book cost me 300 . Green is a tall man with a pair of thick glasses....
U178540780
