问题 填空题

胚胎发育初期所需的营养物质来自______,胚胎发育所需要的养料、氧气通过______和______从母体获得.

答案

精子与卵细胞在输卵管里融合为受精卵,在由受精卵分裂发育成胚泡的过程中,其所需要的营养物质来自卵细胞的卵黄;胚泡进入子宫植入子宫内膜后,胚泡中的细胞继续分裂和分化,逐渐发育成胚胎,胚胎通过胎盘、脐带从母体获得所需要的营养物质和氧气,同时胎儿产生的二氧化碳等废物,也是通过胎盘经母体排出体外的.

故答案为:卵黄;胎盘;脐带

问答题 简答题
问答题 案例分析题

The National Endowment for the Arts recently released the

the results of its “Reading at Risk” survey, which described

movement of the American public away from books and

literature and toward television and electronic media.

According to the survey. “reading is on the decline on every    62.__________

region, within every ethnic group, and at every educational level.“

The day the NEA report released, the U.S. House, in a tie      63.___________

vote, upheld the government's right to obtain bookstore and

library records under a provision of the USA Patriot Act. The

House proposal would have barred the federal government

from demand library records, reading lists, book customer      64.___________

lists and other material in terrorism and intelligence investigations.

These two events are completely unrelated to, yet they      65.___________

echo each other in the message they send about the place of

books and reading in American culture. At the heart

of the NEA survey is the belief in our democratic         66.__________

system depends on leaders who can think critically, analyze

texts and writing clearly. All of these are skills promoted by     67.__________

reading and discussing books and literature. At the same time,

through a provision of the Patriot Act, the leaders of our

country are unconsciously sending the message that reading

may be connected to desirable activities that might        68._________

undermine our system of government rather than helping

democracy flourish.

Our culture's decline in reading begin well before the       69._________

existence of the Patriot Act. During the 1980s' culture wars,

school systems across the country pulled some books from

library shelves because its content was deemed by parents     70.__________

and teachers to be inappropriate. Now what started in schools

across the country is playing itself out on a nation stage and    71.________

is possibly having an impact on the reading habits of the

American public.

在65处填写改错内容。