问题 解答题

据《衢州晚报》报道,我市常山县引进并试种了名为“竹稻”的粮食新品种.竹稻是青皮竹与水稻杂交所得,它们的生殖细胞进行染色体配对,形成受精卵,从而发育成竹稻种子.请回答:

(1)青皮竹与水稻杂交得到竹稻,这种生殖方式属于______生殖(选填“有性”或“无性”).

(2)若某竹稻田中部分生物的食物关系如图所示.从生态系统的成分来看,竹稻属于______.写出其中最短的食物链______.

答案

(1)从本质上讲,是由体细胞进行的繁殖就是无性生殖.主要种类包括:分裂生殖、孢子生殖、出芽生殖、营养生殖(嫁接、压条、扦插等)、组织培养和克隆等. 青皮竹与水稻杂交得到竹稻,经过了两性生殖细胞的结合属于有性生殖.

(2)生态系统中,绿色植物能够通过光合作用制造有机物.有机物中储存着来自阳光的能量.植物制造的有机物,不仅养活了植物自身,还为动物的生存提供食物,是生态系统中的生产者.因此,竹稻属于生产者.

多条食物链相互交织构成食物网,该食物网有3条食物链,分别是竹稻→鼠→鹰;竹稻→鼠→蛇→鹰;竹稻→害虫→青蛙→蛇→鹰.其中最短的食物链是竹稻→鼠→鹰.

故答案为:(1)有性;

(2)生产者;竹稻→鼠→鹰.

单项选择题
问答题

The estimates of the numbers of home-schooled children vary widely. The U. S. Department 0f Education estimates there are 250, 000 to 350, 000 home-schooled children in the country. 4tome-school advocates put the number much higher at about a million.

Many public school advocates take a harsh attitude toward home schoolers perceiving their actions as the ultimate slap for public education and a damaging move for the children. 46) Home schoolers harbor few kind words for public schools, charging shortcomings that range from lack of religious perspective in the curriculum to a herdlike approach to teaching children.

47) Yet, as public school officials realize they stand little to gain by remaining hostile to the home-school population, and as"home schoolers realize they can reap benefits from public schools, these hard lines seem to be softening a bit. Public schools and home schoolers have moved closer to tolerance and, in some cases, even cooperation.

Says John Marshall, an education official, "We are becoming relatively tolerant of’home schoolers." The idea is: "Let’s give the kids access to publid school so they’ll see it’s not as terrible as they’ve been told, and they’ll want to come back."

Perhaps, but don’t count on it, say home-school advocates. 48) Home schoolers oppose the system because they have p convictions that their approach to education -- whether fueled by religious enthusiasm or the individual child’s interests and natural pace, is best.

"The bulk of home schoolers just want to be left alone," says Enge Cannon, associate director of the National Center for Home Education. She says home schoolers choose that path for a variety of reasons, but religion plays a role 85 percent of the time.

Professor Van Galen breaks home schoolers into two groups. 49) Some home schoolers want their children to learn not only traditional subject matter but also strict religious doctrine and a conservative political and social perspective. Not incidentally, they also want their children to learn, both intellectually and emotionally, that the family is the most important institution in

society.

Other home schoolers contend "not so much that the schoolers teach heresy (异教), but that schoolers teach whatever they teach inappropriately," Van Galen writes. 50) "These parents are highly independent and strive to“take responsibility" for their own lives within a society that they define as bureaucratic and inefficient.”

46) Home schoolers harbor few kind words for public schools, charging shortcomings that range from lack of religious perspective in the curriculum to a herdlike approach to teaching children.