托福英语 时间:2007-04-05 我要投稿
【 - 托福英语】


Time: 55 minutes (including the reading of the directions). Now set your clock for 55 minutes.

Question 1-12

??? Orchids are unique in having the most highly developed of all blossoms, in which the usual male and female reproductive organs are fused in a single structure called the column. The column is designed so that a single pollination will fertilize hundreds of thousands, and in some

cases millions, of seeds, so microscopic and light they are easily carried by the breeze. Surrounding the column are three sepals and three petals, sometimes easily recognizable as such, often distorted into gorgeous, weird, but always functional shapes. The most noticeable of the

petals is called the labellum, or lip. It is often dramatically marked as an unmistakable landing

strip to attract the specific insect the orchid has chosen as its pollinator.

???To lure their pollinators from afar, orchids use appropriately intriguing shapes, colors, and scents. At least 50 different aromatic compounds have been analyzed in the orchid family, each blended to attract one, or at most a few, species of insects or birds. Some orchids even change their scents to interest different insects at different times.

???Once the right insect has been attracted, some orchids present all sorts of one-way obstacle

courses to make sure it does not leave until pollen has been accurately placed or removed. By such ingenious adaptations to specific pollinators, orchids have avoided the hazards of rampant

crossbreeding in the wild, assuring the survival of species as discrete identities. At the same time

they have made themselves irresistible to collectors.

1. What does the passage mainly discuss?

(A) Birds

(B) Insects

(C) Flowers

(D) Perfume

2 The orchid is unique because of

(A) the habitat in which it lives

(B) the structure of its blossom