问题 解答题

如图为长颈鹿的进化示意图,请据图回答.

(1)图A说明古代长颈鹿祖先的个体之间颈的长短存在着______,颈的长短是可以______的.

(2)图B说明地球逐渐变得干旱、缺乏青草时,颈长的个体容易获得实物而生存下来.由此可知,颈长的变异相对环境变化而言是______(有利或不利)变异.

(3)图C说明颈长的个体能______下来,并______后代.从进化过程看,这种变异是由于______的改变而引起的.

(4)自然界中的生物,通过激烈的______斗争,______生存,______被淘汰的过程,就是______.

答案

(1))从图A中可以看出,古代的长颈鹿的前肢和颈,有的长,有的短,这是生物的变异现象,这些变异是遗传物质改变引起的,属于可遗传的变异.因此出现以上个体差异的原因是长颈鹿的祖先产了可遗传的变异.

生物界普遍存在着变异,古代的长颈鹿存在着颈长和颈短、前肢长和前肢短的变异,这些变异是可以遗传的.因此,图①说明古代长颈鹿祖先的个体之间颈长存在变异.

(2)图B说明地球环境变得干旱、缺乏青草时,长颈的个体能够吃到高处的树叶,就容易生存下去,并且繁殖后代;短颈的个体,吃不到高处的树叶.由此可知,长颈的变异就是有利变异,短颈的变异是不利变异.

(3)变异是指亲代间和子代个体间的差异,根据变异是否可以遗传,分为可遗传变异和不可遗传变异,遗传物质改变引起的变异属于可遗传的变异,仅由环境因素引起的变异属于不可遗传的变异.不能遗传给后代.图C说明有利变异的个体能生存下来,并繁殖后代,不利变异的个体被淘汰掉.

因此,从进化过程看,这种变异是由于遗传物质发生变化引起的.是可遗传的变异.

(4)自然界中的生物,通过激烈的生存竞争,适应者生存下来,不适应者被淘汰,这就是自然选择.

故答案为:(1)差异;遗传;

(2)有利;

(3)生存;繁殖;遗传物质;

(4)生存;适者;不适者;自然选择.

单项选择题
阅读理解

B

Your body, which has close relations with the food you eat, is the most important thing you own, so it needs proper treatment and proper nourishment(营养). The old saying "An apple a day keeps the doctor away. " is not as silly as some people think. The body needs fruit and vegetables because they contain vitamin C. Many people take extra vitamins in pill form(丸剂), believing that these will make them healthy. But a good diet is made up of nourishing food and this gives all the vitamins you need. The body doesn't need or use extra vitamins, so why waste money on them?

In the modem western world, many people are too busy to bother about eating properly. They throw away the good habits and throw anything into their stomachs, eating hurriedly and carelessly. The list of illnesses caused or made worse by bad eating habits is frightening.

41. From the first sentence we know that ________,

A. all kinds of food you eat can be made into nourishment

B. your body is made up of the food you eat.

C. what you eat has great effect on your health

D. the more you eat, the better you will feel

42. How do you understand the old saying underlined in the passage?

A. Eating apples regularly brings lots of benefits to our health.

B. Doctors are no longer necessary if we eat an apple every day.

C. The apple is the best among all kind of fruits.

D. An apple is a good way to cure illnesses.

43. What can we conclude from the second paragraph?

A. Our bodies need food, or we can't live.

B. Often eating apples is a good habit.

C. Taking extra vitamin pills is completely useless.

D. A good diet is of great importance for our health.

44. In modern western countries, ________.

A. people don't want to pay more attention to their eating

B. lots of people's illnesses are caused or made worse by bad eating habits

C. people throw everything into their stomachs without digestion(消化)

D. people are only too busy to cook meals for themselves

45. If we want to keep healthy, we should ________ .

A. only eat an apple a day       

B. eat properly

C. take as many vitamin pills as possible

D. throw everything into our stomachs slowly and carefully