问题 选择题

基因型为AaBb的豌豆自交,后代中基因型为AaBb的个体占[ ]

A.9/16

B.1/16

C.1/8

D.1/4

答案

答案:D

单项选择题

Dogs are constantly learning from the reaction of human owners, picking up facial cues and anticipating their owner’s behavior, a new research suggests. The findings, published online in the journal Learning and Behavior, show that dogs essentially are always in training, and help explain how many owners unknowingly teach and reward their dog’s bad behavior.

Research conducted at the University of Florida focused on the role of eye contact and facial cues in influencing canine behavior. Earlier studies have suggested that dogs seem to know when they are being watched and even wait to perform forbidden behavior like digging in the garden when they know their owners aren’t looking. In this study, researchers studied how human cues triggered begging behavior among 35 pet dogs, 18 shelter dogs and 8 wolves raised in captivity. First the animals were taught that the human strangers helping with the experiment were reliable sources of tasty treats. The testers stood close together and called to the animal, and both offered rewards of Spam cubes or Beggin’ Strips treats.

After four rewards, the experiment began. Two testers stood against a fence or wall, about 20 feet apart and with food in their pockets. The dog was held about 20 feet away, equidistant from both testers. In one condition, one tester faced the dog while the other turned her back. In another, a tester held a book near her face, while the other tester held the book in front of her face, as if she were reading. In a third condition, one tester held a bucket near the shoulder, while the other put the bucket over her head, blocking her eyes.

Then, both testers called out to the dogs. All the animals—pet dogs, shelter dogs and wolves—ignored the person whose back was turned and sought food from the person who was looking at them. "The question was, are dogs and wolves responsive to a human’s attentional state" said Monique Udell, an assistant professor of psychology at Flagler College, Fla. But when the testers held books, it was only the domestic dogs who avoided the person who appeared to be reading the book. "In a house where they’re used to people reading books, they are sensitive to those types of cues," said Dr. Udell. Interestingly, in the bucket experiment, the animals, for the most part, were equally likely to seek food from the person with the bucket over her head as the person holding the bucket.

The experiment shows that dogs are tuned into whether humans are paying attention. "Dogs don’t have to read our minds. Dogs read our behavior," said Dr. Udell. Pet owners often get frustrated with bad dog behavior without realizing that they themselves have reinforced it, either by giving the dog a treat when they beg, skipping a bath when they protest or letting them sleep on the bed or couch.

The expression "are tuned into" probably means()

A. be ignorant of

B. be insensitive to

C. be responsive to

D. be oblivious to

阅读理解与欣赏

阅读下面的内容,完成下面4题

默契合作的“黑牡丹”   于丽萍

①黑鹳是国家重点保护的珍贵野禽之一,目前的数量十分稀少。它的外形酷似鹤、鹭,长嘴长腿,一对翅膀丰厚宽大,飞翔起来显得极其轻快优雅。它是一种大型涉禽,主食小鱼、小虾、蟹、螺和蛇类、蛙类等,白天喜欢在竹木掩映的河溪之畔散步、觅食和小憩,晚上则成群栖息在高高的树桠上。它体长l米左右,雄鹳除腹肋部的羽毛是纯白色之外,其他与雌鹳一样,均呈深黑色,并泛出一种浓淡变幻、富丽秀美的紫青色光泽,曾被称为鸟中的“黑牡丹”。

②黑鹳是一种十分友爱的野生禽类,配偶之间在共同生活中,合作得十分默契,特别是协力捕鱼的情景,表现得淋漓尽致。

③在一条清澈见底的小溪中,一对比翼飞来的“黑牡丹夫妇”徐徐降落在清流溪畔。个头稍矮的雌鹳,首先警觉地前后扫视一番,就跨入一段较为狭窄的溪中,缩起长脚,静静地伫立着,做好守溪待鱼的准备。个头高大的白肋黑鹳,一直用温柔的朱红色圆眼,看着雌鹳做好了准备,便展翅飞到水面较宽的溪水上游,放开两条健壮的长腿,使劲扑打着翅翼,快速地从溪中朝下奔去,身后溅起了一道白练,“哗哗”地响个不停。溪中的鱼儿,受到雄鹳的惊扰驱使,无不惊恐万状,成群结队地顺流逃选,自然要冲过雌鹳守着的浅水窄口。于是,恭候在一旁的雌鹳,只需举“颈”之劳,便可啄住活蹦乱跳的小鱼、小虾,当做美味。当雌鹳在下游吃饱之后,就会飞向上游,让雄鹳去守口,自己到上游赶鱼下来,让雄鹳也美美地享受一番。

④当然,除了抓小鱼、小虾当“点心”外,“黑牡丹夫妇”还能抓鳝鱼当“大餐”呢。

⑤生活在水田、沼泽淤泥中的鳝鱼,善于拱泥入洞,隐居其中。生性孤癖的鳝鱼,只在夜间出来觅食,白天一般躲着不出来。对于涉禽来说,黄鳝的外表溜滑,易于吞吃,且营养丰富、热能耐久,是难得的美味佳肴。夏秋之交,鳝鱼特别肥腴,自然会成为“黑牡丹夫妇”的捕食对象。“夫妻”俩成天徜徉在黄鳝出没的荒沼野塘中,常以自己的长喙当做犁头,耐心犁开洞穴,寻找着鳝鱼起居留下的蛛丝马迹。一旦发现鳝鱼的泥穴,双方就会轻轻地拍起“翅语”,并配以短促的低叫,示意齐心协力。于是,两只黑鹳摆开围堵的架势,轮番对着泥穴口察看。如发现成功在望,雄鹳就跃入水中,使劲将长喙插入泥穴,朝两边翻动;雌鹳则屏息静气地严阵以待,准备举喙擒捉受惊逃出来的鳝鱼。由于鳝洞一般都打得很深,很难挖掘,雄鹳经常要累得抬头小憩,只好由雌鹳来继续完成。经过反反复复的轮流苦战,终于逼得鳝鱼夺路逃窜。这下子正中“黑牡丹夫妇”的下怀,两鹳立即伸颈夹击,才将鳝鱼擒拿到嘴。

⑥当然,这种功到垂成的概率还是很小的,因为鳝鱼也是个聪明的求生者,常常是“狡兔三窟”。当“黑牡丹夫妇”在洞外忙得热火朝天的时候,滑溜溜的鳝鱼早已悄悄溜走了。“夫妻”俩运气不好,苦苦地折腾了大半天,却是徒劳无功。遇到这种情况,雄鹳便显得暴躁不已,连连仰天长鸣,并使劲儿用翅膀抽打着水面。雌鹳却很有耐心,常常柔声柔气地应答着,紧紧地依偎在“丈夫”的身旁,不停地用翅膀梳理着“丈夫”的羽毛,极力安抚它。经过雌鹳一番安慰,雄鹳的情绪开始稳定下来,恢复了平静。接着,就交头接耳一番,似乎又有了好主意。一会儿,双双展翅飞起,在绿野清流的视野里,两只优雅的“黑牡丹”飞向新的地方。

(选自《科学之友》)2009年第4期)

小题1:本文第二自然段在文中有何作用?请简要分析。(4分)

小题2:文章最后一段说,“鳝鱼也是个聪明的求生者”,作者为什么这样说?(4分)

小题3:“黑鹳是一种十分友爱的野生禽类,配偶之间在共同生活中,合作得十分默契”,从全文来看,黑鹳的“友爱”和“默契”主要表现在哪些方面?(4分)

小题4:作为科普文章,本文写法上有哪些特点?请举例加以赏析(答出两条即可)。(6分)