问题 选择题

与植物有性生殖相比,植物营养生殖的优点是(  )

A.能保持亲本的优良性状提高后代的生活力

B.能综合双亲的优良特点提高后代的生活力

C.能保持亲本的优良特点加快生殖的速度

D.能综合双亲的优良特性加快生殖的速度

答案

无性生殖指不经过两性生殖细胞的结合,由亲本直接产生子代的生殖方式.优点是繁殖速度快,有利于亲本性状的保持,缺点是因为子代和母代遗传特性毕竟无变化,变异性降低,适应环境变化的能力便降低.无性生殖主要有:1、分裂生殖,又叫裂殖,是生物由一个母体分裂出新子体的生殖方式.常见于单细胞生物(分裂即生殖);2、出芽生殖,又叫芽殖,是由母体在一定的部位生出芽体,芽体逐渐长大,形成与母体一样的个体,并从母体上脱落下来,成为完整的新个体的生殖方式.常见于水螅和酵母菌.3、孢子生殖,有的生物,身体长成以后能够产生一种细胞,这种细胞不经过两两结合,就可以直接形成新个体.这种细胞叫做孢子,这种生殖方式叫做孢子生殖.常见于低等植物和真菌.4、营养生殖,由植物体的营养器官(根、叶、茎)产生出新个体的生殖方式,叫做营养生殖.

有性生殖是指由两性细胞结合形成受精卵,然后由受精卵发育成新个体的生殖方式,有性生殖可以使后代产生更大的变异,使后代产生新的性状,生活力比较强,更有利于适应环境,有利于种族的繁衍.

故选C

阅读理解

I really love my job because I enjoy working with small children and like the challenges and awards from the job. I also think my work is important. I wasn’t an excellent student because I didn’t do much schoolwork. In my final term I started thinking what I might do and found I didn’t have much to offer.

I then found myself a job, looking after two little girls. It wasn’t too bad at first. But the problems began when I agreed to live in. I would be there if my boss had to go out for business in the evening. We agreed that if I had to work extra hours one week, she’d give me time off the next. But unluckily, it didn’t often work out. I was getting very tired. Because I had too many late nights and early mornings with the children.

One Sunday, I was in the park with the children, and met Megan who used to go to school with me. I told her about my situation. She suggested that I should do a course and get a qualification(资格证书)if I wanted to work with children. I didn’t think I would be accepted because I didn’t take many exams in school. She asked me to phone the local college and they were really helpful. My experience counted for a lot and I got on a part-time course. I had to leave my job with the family, and got work helping out at a kindergarten.

Now I’ve got a full-time job there. I shall always be thankful to Megan. I wish I had known earlier that I could have a success, even if I am not top of the class at school.

小题1:What do you think of the writer when she was a student?

A.An excellent student

B.A hardworking student

C.A bad student

D.A lazy student小题2:What is the writer’s first job?

A.A cleaner

B.A babysitter

C.An assistant

D.A teacher小题3: When staying with the two girls’ family,the writer ________.

A.was paid for extra work

B.often worked long hours

C.got much help from her boss

D.took a day off every other week小题4: Why did the writer leave her first job?

A.She found a full-time job.

B.She was fed up with children.

C.She decided to attend a part-time course.

D.She needed a rest after working extra hours.小题5:What has the writer learned from her own experiences?

A.Less successful students can still have a success.

B.Qualifications are necessary for a job.

C.Hard work makes an excellent student.

D.One must choose the job she like.

单项选择题