问题 选择题

细菌和真菌的共同特征是(  )

A.都是单细胞

B.都具有细胞核

C.都不含叶绿体

D.都是分裂生殖

答案

细菌的基本结构有细胞壁、细胞膜、细胞质和DNA集中的区域,没有成形的细胞核,没有叶绿体;细菌都是单细胞的,细菌是靠分裂进行生殖的,也就是一个细菌分裂成两个细菌.长大以后又能进行分裂.在环境适宜的时候,不到半小时,细菌就能分裂一次.真菌的基本结构有细胞壁、细胞膜、细胞质、细胞核,没有叶绿体.真菌有单细胞的,也有多细胞的;孢子生殖,孢子落到适宜的环境就会萌发生出菌丝,形成新个体.大多数真菌用孢子繁殖后代.因此细菌、真菌的共同特征是细胞内没有叶绿体,异养.

A、细菌都是单细胞的,而真菌有单细胞的如酵母菌,也有多细胞的如霉菌.故不符合题意.

B、细菌细胞内没有成形的细胞核,而真菌有成形的细胞核故不符合题意.

C、细菌、真菌细胞内都没有叶绿体,营养方式是异养,有寄生,也有腐生.故符合题意.

D、细菌是分裂生殖,真菌是孢子生殖.故不符合题意.

故选:C.

选择题
阅读理解

Parents who feel disappointed at their teenagers’ failure to pay attention in class, and inability to sit quietly long enough to finish homework or plan ahead, should take solace. Their children are not being lazy or careless, according to new research.

The research has found that teenagers’ brains continue developing far longer into adulthood than we used to think. Teens may look like young adults but their brain structure is similar to that of much younger children.

“It is not always easy for teens to pay attention in class without letting their minds wander, or to ignore distractions from their younger brothers or sisters when trying to solve a maths   problem,” said Dr Iroise Dumon-theil. “But it’s not the fault of teenagers that they can’t pay attention and are easily distracted. It’s to do with the structure of their brains. Teens simply can’t think as well as an adult.”

The research showed that the brain of a teenager works less effectively than that of an adult. “We knew that the front of the brain of teens functioned in a chaotic  (混乱的) way but we  didn’ t realize it continued until the late 20s or early 30s,” said Dr Sarah-Jayne Blakemore, who led the research.

Chaotic thought patterns are a result of teenagers’ brains containing too much grey matter — the cell bodies and connections which carry messages within the brain. As we age, the amount of grey matter in our brain reduces.

“What our research has shown is that there is simply too much going on in the brains of teens,” said Blakemore. “The result is that their brain energy and resources are wasted and their decision-making process is badly influenced. Adults, on the other hand, have less grey matter. This means that the brain works far more effectively.”

小题1:The underlined word “solace” in Paragraph 1 may mean _____.

A. notice

B.medicine

C.comfort

D.action小题2:When making decisions, _____.

A.teens’ brains continue to do much needless work

B.the grey matter in young children’s front brain becomes active

C.people are not likely to be distracted until their late 30s

D.adults are more independent than teens小题3:What is the effect of having too much grey matter?

A.It makes us always feel disappointed.

B.It makes us more intelligent.

C.It had a bad effect on the growth of teens.

D.It had a bad effect on decision-making.小题4:What’s the text mainly about?

A.Teens have different brains from those of children.

B.Adults work more effectively than teens.

C.Grey matter makes teens unable to pay attention.

D.Brain energy is wasted in the brain’s activity.