2017年6月3日托福阅读真题+题目+答案：Spider Silk and Evolution

2017年6月3日托福阅读真题+题目+答案：Spider Silk and Evolution

Insects, which are fewer in number than spiders, have undergone considerable transformations on their way to evolutionary success: they are hugely various in body type and life ways. By comparison, the forty million species of spiders – all predators with a basically similar body plan – may seem boring. Yet this is exactly what is so startling about spiders. Without undergoing major outward bodily change since they first evolved, spiders have nonetheless adapted to a vast array of conditions. Silk has made the spider’s adaptation to different environments possible. As spiders evolved, they developed many ways of using silk: to protect themselves and their eggs, to detect and catch prey, and to travel to new habitats. They use some silks as glues, some as watertight packaging, some as climbing rope, and some as super-flexible, impact-absorbing share netting. When spiders use silk as webs, they are able to extend their energy, their senses, and even their physical reach without changing the outlines of their anatomy.

1. The word “considerable” in the passage is closet in meaning to

A) significant

B) various

C) complex

D) surprising

2. According to paragraph 1, what makes it surprising that spiders have adapted to different environments?

A) Spider webs do not function well in watery conditions.

B) Spiders have a relatively limited physical reach.

C) Spiders have kept the same basic body shape throughout their history.

D) The behavior of the insects that spiders prey on can vary greatly depending on the conditions.

Spiders also have the unique ability to make more than one kind of silk. “Living-fossil” spiders, meaning spiders that are almost identical to some of the oldest spider fossils yet found, make only a few different silks. Spiders that have evolved more recently, however, have six or more different silks at their disposal. Each is produced in a different type of gland and used for a different purpose. Each appearance of a major new type of silk correlates with explosive growth in the number of spider species. These new silk seem to have allowed spiders to forge trails into new ecological niches where they did not have to compete with ancestral spider species.

3. According to paragraph 2, which of the following is NOT true of spiders and their silk?

A) The first spiders were able to produce more types of silk than can recently evolved spiders.

B) Recently evolved spider species can product at least six types of silk.

C) Modern spiders produce each type of silk in a different gland.

D) Spiders are the only life-form able to make more than one kind of silk.

4. According to paragraph 2, the fact that each major new type of silk correlates with a huge growth in the number of spider species suggests that

A) the ancestors of “living-fossil” spiders made fewer types of silk than “living-fossil” spiders do

B) each new spider species had more silk glands than the species from which it evolved

C) the earliest spider species were less well adapted to their environments than modern spider species are to theirs

D) new silk varieties allowed spiders to become established in environments previously unoccupied by spiders

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