题目内容

6、When you watch TV programmes about wild animals, it is amazing to see how an antelope can escape a lion’s attack. In the wilderness, everyone has a stunt(绝技). Even plants have their own ways of fighting off enemies.

Over millions of years of evolution, plants have developed a unique defence system. Chemicals are widely used for survival, By making their leaves, flowers, stems, roots and fruits distasteful or poisonous to predators(食肉动物), plants can fight back.

One such plant is the Gold Wattle tree. British botanist David Cameron has found that when an animal eats the tree’s leaves, the amount of poisonous tannin(丹宁酸) increases in the other leaves. “It’s like the damaged leaves telephoning the others telling them to fight together against the enemy,” he said.

The tree also sends defence messages to neighboring plants by giving out a special smell. Golden Wattle tress in the surrounding 45 meters will get the message and produce more tannin within 10 minutes. Now, if a predator eats too many of the trees’ leaves, it will die.

Every species of plant or tree specializes in the production of a particular set of chemicals. A herbivore(草食动物) that can safely eat the leaves of one tree may be poisoned by its neighbor.

In this way, plants have developed not only individual defence systems, but also shared it with others. This makes it impossible for a single predator to destroy even a small area of forest.

1．According to the passage, which of the following statements about the Golden Wattle tree is NOT correct?

       A．It is only poisonous while it is being attacked.

       B．It has the ability to warn its neighboring plants of danger.

       C．It fights off its enemies by producing poisonous chemicals.

       D．An animal that eats too many of its leaves may be poisoned to death.

2．It is impossible for a single predator to destroy even a small area of forest mainly because ___.

       A．plants will become poisonous if they are attacked.

       B．plants have very good individual defence systems.

       C．plants can protect themselves and share their defence systems.

       D．plants can give out special smell to fight off their enemies.

3．What does David Cameron mean in paragraph 3?

       A．He means that leaves of Golden Wattle trees can speak to each other.

       B．He intends to emphasize that the defence system of Golden Wattle is quick and effective.

       C．He wants to indicate that the Golden Wattle leaves are very clever.

       D．He is explaining how the Golden Wattle tress warn each other when they are attacked.

4．According to the writer, the unique defence system of plants is the result of ______.

       A．millions of years of evolution.

       B．the tough natural environment.

       C．their outstanding poison producing system.

       D．large numbers of herbivores in the wilderness.

5．From the passage, we learn that __________.

       A．All the plants or trees are poisonous.

       B．Every plant or tree produces its particular chemicals.

       C．All the plants or trees produce the same chemicals.

       D．Every species of plant or tree produces its particular chemicals.