Paragraph 3
The environmental conditions of freshwater habitats, unlike those of ocean habitats, are highly variable. Water temperature can fluctuate seasonally or even daily and changing level of rainfall can lead to fluctuations in the concentration of chemical in the water or even to period in which the aquatic habitat dries up. Ancient fresh water green algae must have evolved features that enable them to withstand extremes of temperature and periods of dryness. These adaptations served their descendant well as they invaded land.
4、What can be inferred from paragraph 3 about ancient green algae?
They lived in a generally wet environment that was sometimes dry
They adapted better to changes in water temperature than did to other changes in the environment.
They inhabited areas that were close to the ocean.
They had lived primarily on land
Paragraph 4
The terrestrial world is green now, but it did not start out that way. When plants first made the transition ashore more than 400 million years ago, the land was barren and desolate, inhospitable to life. From a plant's evolutionary view point, however, it was also a land of opportunity, free of competitors, and predator arid full of carbon dioxide and sunlight (the raw materials for photosynthesis, which are present in far higher concentrations in air than in water). So once natural selection had shaped the adaptations that helped plants overcome the obstacles to terrestrial living, plants prospered and diversified.
5、The word "desolate in the passage is closest In meaning to
dusty
hardened
deserted
dried out
6、 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.
Terrestrial plants had the advantages of not having rivals and having easy access to photosynthetic material
The abundance of photosynthetic material made life on land easier for pioneering plants
Once plants had eliminated their competitors and their predators, their evolutionary process proceeded smoothly.
Plant evolution eliminated competitors and made the process of photosynthesis more efficient.
7、According to paragraph 4, which of the following is true about the terrestrial world at the time it was colonized by plants?
it was exposed to high levels of solar radiation
it contained a limited supply of carbon dioxide
it had developed 400million years earlier
it lacked the presence of any organisms
Paragraph 5
When plants pioneered the land, they faced a range of challenges posed by terrestrial environments. On land, the supportive buoyancy of water is missing, the plant is no longer bathed in a nutrient solution, and air tends to dry things out. These conditions favored the evolution of the structures that support the body, vessels that transport water and nutrients to all parts of plant, and structures that conserve water. The resulting adaptations to dry land include some structural features that arose early in plant evolution; now these features are common to virtually all land plant. They include roots or root like structures, a waxy cuticle that covers the surfaces of leaves and stems and limits the evaporation of water, and pores called stomata in leaves and stems that allow gas exchange but close when water is scarce, thus reducing water loss. Other adaptations occurred later in the transition to terrestrial life and now wide spread but not universal among plants. These include conducting vessels that transport water and minerals upward from the roots and that move the photosynthetic products from the leaves to the rest of the plant body and the stiffening substance lignin, which support the plant body, helping it expose maximum surface area to sunlight.
8、the word "posed" in the passage is closest in meaning to
shared
presented
strengthened
concealed
9、According to paragraph 5, all of the following are problems that early terrestrial plants had to overcome Except
a tendency to become dry
the inability to limit surface sunlight
the absence of a structure to support the body of the plant
the inability to transport water and minerals through the plant minerals
10、What purpose does paragraph 5 serve in the larger discussion of the origins of terrestrial plants?
To emphasize how long it took for ancestral plants to adjust to life on land
To disprove the argument that land plants adapted easily to their new terrestrial environment
To explain how plant colonization changed the physical environment of the terrestrial world
To describe how ancestral plants solved the problems they confirmed in colonizing
