问题 问答题 简答题

在水产种苗培育中,将不同产地的卤虫卵孵出的无节幼体喂养养殖动物幼体时,出现幼体生长率和成活率有明显差异的现象,请分析其可能原因,对策如何?

答案

参考答案:

可能原因:①不同产地的卤虫卵其营养价值是不同的。②目前的研究认为,不同产地的卤虫卵及其孵出的无节幼体的营养价值的差异主要表现在高度不饱和脂肪酸含量上的差异。根据卤虫卵及其孵出的无节幼体的高度不饱和脂肪酸含量的不同,可分为海水型和淡水型的卤虫卵。③水产幼苗的生长发育和存活需要足够的高度不饱和脂肪酸。各种水产幼苗对高度不饱和脂肪酸的需求种类是不同的。④不同产地的卤虫卵孵出的无节幼体的个体大小是不同的,各种水产幼苗对无节幼体的个体大小的需求是不同的。

对策:①选用合适的卤虫休眠卵。营养价值高;个体大小适宜。②对孵出的无节幼体进行营养强化,然后再投喂给幼苗。

单项选择题
填空题

Part 3


Questions 19-25


·Read the following passage and answer questions 19-25.
·For questions 19-25, choose the correct answer from A, B, C and D.
·Markyour answers on the Answer Sheet.
It is natural for young people to be critical of their parents at times and to blame them for the most of the misunderstandings between them. They have always complained, more or less justly, that their parents are out of touch with modern way; that they are possessive and dominant; that they don’t trust their children to deal with the crisis; that they talk too much about certain problems — and that they have no sense of humor, at least in parent-child relationships.
I think it is true that parent often underestimate their teenage children and also forget how they themselves felt when young.
Young people often irritate their parent with their choices in clothes and hairstyles, in entertainers and music. This is not their motive. They feel cut off from adult world into which they have not yet been accepted. So they create a culture of society of their own. Then, it turns out that their music and entertainers or vocabulary or clothes or hairstyles irritate their parents. This gives them additional enjoyment. They feel they are superior, at least in a small way, and they are leaders in style and taste.
Sometimes you are resistant, and proud because you don’t want your parents to approve what you do. If they did approve, it looks as if you are betraying your own age group. But in that cases, you are assuming that you are an underdog: you can’t win but at least you can keep your honor. There is a passive way of looking at things. It is natural enough after long years of childhood, when you are completely under your patents’ control. But it ignores the face that you are now beginning to be responsible for yourself.
If you plan to control your life, cooperation can be part of that plan. You can charm others, especially your parents, into doing things the way you want. You can impress your parents with your sense of responsibility and initiative, so that they will give you the authority to do what you want to do.

According to the author, which statement the passage didn’t refer to

A.Parents often underestimate their teenage children.

B.Young people make their parents angry because their choices in clothes and hairstyles.

C.Young people want to communicate with their parents.

D.Teenagers don’t want their parents to approve of what they do.