托福阅读真题+题目+答案：The ecology of Kirtland's Warbler

托福阅读真题+题目+答案：The ecology of Kirtland's Warbler

By the early 1970s, songbirds known as Kirtland's warblers were under threat of extinction.▋ Scientists began to investigate what was responsible for their decline. ▋Kirtland's warblers winter in the Bahamas and then fly north to the state of Michigan in the United States, where they breed in an exacting set of conditions in jack-pine woodlands ▋Although jack-pine trees grow widely throughout the northern coniferous forests, Kirtland's warblers nest only in jack-pine woods on one soil type, called Grayling sands, which occurs in central Michigan at the very southern end of the jack-pine range.▋ These warblers build their nests on the ground and, apparently because the nests must remain dry, prefer to build them on dead tree branches still attached to a tree at ground level, and only on coarse, sandy soil that drains away rainwater rapidly. Young jack pines provide the dead branches at the ground surface, and Kirtland's warblers are known to nest only in jack-pine woodlands that are between 6 and 21 years old, ages when the trees, 5 to 20 feet tall, retain dead branches at ground level.Males are territorial, and each defends an area as large as 80 acres in a uniform jack-pine stand.

1.According to paragraph 1. which of the following is NOT mentioned as necessary in order for Kirtland's warblers to build their nests?

A.Soil that does not allow water to remain

B.Nearby supplies of clean rainwater

C.Dead tree branches still attached to the tree

D.Trees that have grown to a height of 5 to 20 feet

2.Which of the following can be inferred from paragraph 1 about why Kirtland's warblers do not nest in woodlands older than 21 years?

A.Their offspring cannot survive in nests that are more than 20 feet off the ground.

B.They cannot easily defend woodland areas that have become heavily populated with trees.

C.The ground-level branches that they need are no longer available in older woodlands.

D.They nest on a type of sand found mostly in relatively young forests.

These requirements leave the warbler with few nesting areas, all the fewer because jack pine is a "fire species"-it persists only where there are periodic forest fires. Jack-pine cones open and expose their seeds only after they are heated by fire, and the trees are intolerant of shade, able to grow only when their leaves can reach into full sunlight.Even if seeds were to germinate under mature trees, the seedlings could not grow in the shade and would die. Jack pine produces an abundance of dead branches that promote fires, which is interpreted by some as an evolutionary adaptation to promote those conditions most conducive to the survival of the species.
3.3.According to paragraph 2, what is one reason why fire is important for the survival of jack pines?

A.Fire makes it possible for jack-pine cones to release their seeds.

B.Fire produces many dead branches from which warblers build nests.

C.Fire prevents cone seeds from maturing into seedlings too soon.

D.Fire helps scatter jack-pine cones and seeds to new areas.

。。。。。余下托福阅读真题原文及题目答案省略！

托福阅读真题+题目+答案：The ecology of Kirtland's Warbler完整版下载，10元有偿！