问题 实验题

图中表示人的受精及胚胎发育过程,请据图回答:

 

(1)A是       ,它含有的染色体数是          

(2)B是 _________, C的染色体数目是 ________。

(3)亲代的遗传物质是通过 _____________ 这一“桥梁”传给子代的。

(4)D表示 __________ 过程。胎儿通过 __________ 和脐带从母体获得营养。

答案

(1)精子    23(2)卵巢     23对(或:46条)(3)生殖细胞(或:精子和卵细胞;配子)(4)受精    胎盘

题目分析:(1)睾丸的主要功能是产生精子和分泌雄性激素,因此A是精子;在形成生殖细胞的过程中,成对的染色体分开,每对染色体中的一条进入精子或卵细胞中,因此生殖细胞中的染色体数比体细胞中的少一半,正常人的体细胞染色体数目为23对,因此生殖细胞精子、卵细胞中的染色体的数目是23条是体细胞的一半。

(2)卵巢的主要功能是产生卵细胞、分泌雌性激素,B能产生卵细胞因此B是卵巢,精子与卵细胞相融合形成受精卵的现象叫做受精,图示中C细胞是受精卵,受精卵的染色体数又恢复到父母的体细胞的染色体数目即46条。

正常人的体细胞染色体数目为23对,并有一定的形态和结构,B卵巢内的细胞为体细胞,染色体数为23对。

(3)遗传物质位于染色体上,染色体在亲子代之间的传递就实现了遗传物质的传递,亲代的染色体是通过生殖细胞传递给子代的,在有性生殖过程中,精子与卵细胞就是遗传物质在亲子代间传递的桥梁。

(4)精子与卵细胞相融合形成受精卵的现象叫做受精,因此D表示受精,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,因此胎儿通过胎盘和脐带从母体获得营养。

点评:此题综合性强,涉及的知识点多,有一定的难度,解答此类题目的关键是理解生殖过程中染色体数目的变化。

填空题
阅读理解

It was raining as I got off the train in Nashville, Tennessee. I was tired so I went straight to my hotel.

A big, heavy man was walking up and down in the hotel lobby. Something about the way he moved made me think of a hungry dog looking for a bone. He had a big, fat, red face and a sleepy expression in his eyes. He introduced himself as Wentworth Caswell – Major Wentworth Caswell – from “a fine southern family”. Caswell pulled me into the hotel’s barroom and yelled for a waiter. We ordered drinks. While we drank, he talked continually about himself, his family, his wife and her family. He said his wife was rich. He showed me a handful of silver coins that he pulled from his coat pocket.

By this time, I had decided that I wanted no more of him. I said good night.

I was born in the south myself. But I live in New York now. I write for a large magazine. My boss had asked me to go to Nashville. The magazine had received some stories and poems from a writer in Nashville, named Azalea Adair. The editor liked her work very much. The publisher asked me to get her to sign an agreement to write only for his magazine.

I left the hotel at nine o’clock the next morning to find Miss Adair. It was still raining. As soon as I stepped outside I met Uncle Caesar. He was a big, old black man with fuzzy gray hair. Uncle Caesar was wearing the strangest coat I had ever seen. It must have been a military officer’s coat. It was very long and when it was new it had been gray. But now rain, sun and age had made it a rainbow of colors. Only one of the buttons was left. It was yellow and as big as a fifty cent coin.

Uncle Caesar stood near a horse and carriage. He opened the carriage door and said softly, “Step right in, sir. I’ll take you anywhere in the city.”

“I want to go to 861 Jasmine Street,” I said, and I started to climb into the carriage. But the old man stopped me. “Why do you want to go there, sir?”

“What business is it of yours?” I said angrily. Uncle Caesar relaxed and smiled. “Nothing, sir. But it’s a lonely part of town. Just step in and I’ll take you there right away.”

861 Jasmine Street had been a fine house once, but now it was old and dying. I got out of the carriage.

“That will be two dollars, sir,” Uncle Caesar said. I gave him two one-dollar bills. As I handed them to him, I noticed that one had been torn in half and fixed with a piece of blue paper. Also, the upper right hand corner was missing.

小题1:The narrator (故事的叙述者)got to Nashville probably _______.

A.in the morning

B.at noon

C.in the afternoon

D.in the evening小题2: The narrator didn’t like Caswell mainly because of ________.

A.his appearance

B.his family

C.the way he talked and behaved

D.his wife小题3: The publisher told the narrator to go to Nashville ______.

A.to get a writer to sign an agreement for his magazine

B.to collect some stories and poems from a writer

C.to look for good writers for his magazine

D.to visit his old friend Azalea Adair小题4: Uncle Caesar’s strange coat ________.

A.was worn by a military officer

B.was a new gray coat

C.was an old yellow raincoat

D.had only one button left小题5: From the question “Why do you want to go there, sir?”, we guess that Uncle Caesar _______.

A.wanted to know why the narrator wanted to go there

B.knew the place and was concerned about the narrator

C.would charge two dollars for taking the narrator there

D.must have lived in the neighbourhood before