题干

睾丸产生的精子和卵细胞产生的卵细胞都是____;精子和卵细胞结合形成____,它不断进行细胞分裂,逐渐发育成________缓慢地移动到子宫中,最终附着在子宫内膜上,并继续进行细胞分裂和分化,逐渐发育成____,在第8周左右发育成____,一般来说,从形成受精卵开始到第38周(266天)时,____就发育成熟了.

上一题 下一题 0.0难度 选择题 更新时间:2019-03-26 05:01:07

答案(点此获取答案解析)

生殖细胞,受精卵,胚泡,胚泡,胚胎,胎儿,胎儿

同类题3

阅读理解

    Parents and kids today dress alike, listen to the same music, and are friends. Is this a good thing? Sometimes, when Mr. Ballmer and his 16-year-old daughter, Elizabeth, listen to rock music together and talk about interests both enjoy, such as pop culture, he remembers his more distant relationship with his parents when he was a teenager.

    “I would never have said to my mom, 'Hey, the new Weezer album is really great. How do you like it?''' says Ballmer. “There was just a complete gap in taste.”

    Music was not the only gulf. From clothing and hairstyles to activities and expectations, earlier generations of parents and children often appeared to move in separate orbits.

    Today, the generation gap has not disappeared, but it is getting narrow in many families. Conversations on subjects such as sex and drugs would not have taken place a generation ago. Now they are comfortable and common. And parent-child activities, from shopping to sports, involve a feeling of trust and friendship that can continue into adulthood.

    No wonder greeting cards today carry the message, “To my mother, my best friend.”

    But family experts warn that the new equality can also result in less respect for parents. “There's still a lot of strictness and authority on the part of parents out there, but there is a change happening,” says Kerrie, a psychology professor at Lebanon Valley College. “In the middle of that change, there is a lot of confusion among parents.”

    Family researchers offer a variety of reasons for these evolving roles and attitudes. They see the 1960s as a turning point. Great cultural changes led to more open communication and a more democratic process that encourages everyone to have a say.

    “My parents were on the 'before' side of that change, but today's parents, the 40-year-olds, were on the 'after' side,” explains Mr. Ballmer, “It's not something easily accomplished by parents these days, because life is more difficult to understand or deal with, but sharing interests does make it more fun to be a parent now.”