托福阅读真题+题目+答案：The Development of Land Flora

托福阅读真题+题目+答案：The Development of Land Flora

Today's most primitive land plants, the liverworts and hornworts, have patterns in their DNA that indicate a connection to a group of complex green algae that are found only in freshwater, which suggests that land plants arose in freshwater lakes and streams or from river deltas-not from the ocean shore. But what might have caused a plant to adapt to the harshness of a land environment? The most reasonable scenario suggests that early land plants lived along streams or in ponds that dried up during part of the year. Their first adaptation was the spore, a reproductive cell that could survive this dry period. Carried by the wind, the microscopic spore could be scattered across wide areas, germinating (starting to grow)—if lucky -in a distant pool of quiet water or moist mud. ⬛Such spores are the first evidence of plants living on land.

1. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

A  Liverworts and hornworts, which are today's most primitive land plants, have patterns in O their DNA that indicate a connection to a group of complex green algae found only in freshwater.

B  Unlike other land plants, liverworts and hornworts arose in lakes and streams, and the O proof is that DNA patterns indicate that they have descended from a group of freshwater green algae.

C  A connection indicated by DNA patterns between today's most primitive land plants and a O group of green algae found only in freshwater suggests that land plants arose in freshwater habitats.

D  DNA similarities between the most primitive land plants, the liverworts and hornworts, suggest that today's land plants arose in freshwater habitats rather than the ocean shore.

2. The word "harshness”  in the passage is closest in meaning to

A  complexity

B  severity

C  newness

D  dryness

⬛Earlier, blue-green bacteria probably lived on damp soil and in shallow pools over hundreds of millions of years. ⬛They were probably joined by green algae and fungi to form puddles of green glop in moist depressions and along the edges of ponds and streams. ⬛These lineages (lines of descent) may have populated land surfaces for many millions of years before more complex land plants arose. And they, too, had to develop sporelike stages to survive drying out and achieve dispersal. Unfortunately, because they did not possess resistant tissues, these early forms of land flora left no trace in the fossil record. The first "true" land plants were probably flat liverwort- like plants with little leaves only one cell layer thick. Again, these first land plants are remembered in the rocks only by their spores. Being able to withstand the physical stresses of drying and rehydration, the tough spore wall is also resistant to decomposition. Thus, spores became an important element in the fossil record. Algal and fungal spores are quite different from these. These early spores are first recorded in the rocks dated at around 470 million years ago, and they are usually found as groups of four (called tetrads). By about 430 million years ago, spore tetrads declined in abundance and separate individual spores with a Y-shaped (trilete) configuration on one side became common.

。。。。。。余下托福阅读真题及答案省略！

托福阅读真题+题目+答案：The Development of Land Flora，10元有偿下载本篇完整版阅读真题！