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
本文为大家准备了
托福TPO25阅读试题及答案，便于考生托福备考。
The Evolutionary Origin of Plants
Paragraph 1
The evolutionary history of plants has been marked 1 a series of
adaptations. The ancestors of plants were photosynthetic
single-celled organisms that gave rise to plants presumably lacked
true roots, stems, leaves, and complex reproductive structures such
as flowers. All of these features appeared later in the
evolutionary history of plants. Of today's different groups of
algae, green algae are probably the most similar to ancestral
plants. This supposition stems from the close phylogenetic (natural
evolutionary) relationship between the two groups. DNA comparisons
have shown that green algae are plants' closest living relatives.
In addition, othef lines of evidence support the hypothesis that
land plants evolved from ancestral green algae used the same type
of chlorophyll and accessory pigments in photosynthesis as do land
plants. This would not be true of red and brown algae. Green algae
store food as starch, as do land plants and have cell walls made of
cellulose, similar in composition to those of land plants. Again,
the good storage and cell wall molecules of red and brown algae are
different.
Paragraph 2
Today green algae live mainly in freshwater, suggesting that
their early evolutionary history may have occurred in freshwater
habitats. If so, the green algae would have been subjected to
environmental pressures that resulted in adaptations that enhanced
their potential to give rise to land-dwelling or organisms.
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.
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.
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
Paragraph 6
These adaptations allowed an increasing diversity of plant forms
to exploit dry land. Life on land, however, also required new
methods of transporting sperm to eggs. Unlike aquatic and marine
forms, land plants cannot always rely on water currents to carry
their sex cells and disperse their fertilized eggs. So the most
successful groups of land plants are those that evolved methods of
fertilized sex cell dispersal that are independent of water and
structures that protest developing embryos from drying out.
Protected embryos and waterless k dispersal of sex cells were
achieved with the origin of seed plans and the key evolutionary
innovations that they introduced: pollen, seeds, and later, flowers
and fruits.
Paragraph 1
The evolutionary history of plants has been marked a series of
adaptations. The ancestors of plants were photosynthetic
single-celled organisms that gave rise to plants presumably lacked
true roots, stems, leaves, and complex reproductive structures such
as flowers. All of these features appeared later in the
evolutionary history of plants. Of today's different groups of
algae, green algae are probably the most similar to ancestral
plants. This supposition stems from the close phylogenetic (natural
evolutionary) relationship between the two groups. DNA comparisons
have shown that green algae are plants' closest living relatives.
In addition, other lines of evidence support the hypothesis that
land plants evolved from ancestral green algae used the same type
of chlorophyll and accessory pigments in photosynthesis as do land
plants. This would not be true of red and brown algae. Green algae
store food as starch, as do land plants and have cell walls made of
cellulose, similar in composition to those of land plants. Again,
the good storage and cell wall molecules of red and brown algae are
different.
1、the word 'presumably' in the passage is closest in meaning
to
Originally
supposedly
Obviously
Usually
2、According to paragraph 1, all of the following are true of
ancestral plants EXCEPT f
They had cellulose-based cell walls.
They were closely related to green algae
They were able to store nutrients
They had a sophisticated multicellular structure.
Paragraph 2
Today green algae live mainly in freshwater, suggesting that their
early evolutionary history may have occurred in freshwater
habitats. If so, the green algae would have been subjected to
environmental pressures that resulted in adaptations that enhanced
their potential to give rise to land-dwelling or organisms.
3、The phrase 'subjected to' in the passage is closest in
restricted by
distant from
exposed to
combined with
Paragraph 6
These adaptations allowed an increasing diversity of plant forms to
exploit dry land. Life on land, however, also required new methods
of transporting sperm to eggs. Unlike aquatic and marine forms,
land plants cannot always rely on water currents to carry their sex
cells and disperse their fertilized eggs. So the most successful
groups of land plants are those that evolved methods of fertilized
sex cell dispersal that are independent of water and structures
that protest developing embryos from drying out. Protected embryos
and waterless dispersal of sex cells were achieved with the origin
of seed plans and the key evolutionary innovations that they
introduced: pollen, seeds, and later, flowers and fruits.
11、According to Paragraph 6, The adaptation made by terrestrial
plants had which of the following effect?
Plants developed reproductive strategies usable in both land and
water environment
The plant diversity achieved in water environments diminished on
land
Seed plants became the dominant species among plants
A greater range of plants was able to develop
12、Which of the following best describes the author's
presentation of the information about land plants?
The author provided and overview of the evolutionary
relationships between specific species of algae and land
plants
The author discusses the transformation plants underwent in the
process of changing from an aquatic to a terrestrial
environment
The author establishes a pattern of similarity between major land
and water pant groups
The author resents evidence to support the hypothesis that plants
first fully evolved in water before finding their way to land
13、Look at the four squares that indicate where the following
sentence could be added to the passage.
Scientists believe that chemical changes and a thicker
exterior, among other things, may have helped ancient algae
overcome the conditions in their environment.
Where would the sentence best fit?
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.
D
14、 Directions: An introductory sentence for a brief summary of
the passage is provided below. Complete the summary by selecting
the THREE answer choices that express the most important ideas in
the passage. Some sentences do not belong in the summary because
they express ideas that not presented in the passage or are minor
ideas in the passage. This question is worth 2 points.
In moving from water to land, ancestral plants overcame
many obstacles in order to survive.
A． Neither brown nor red algae are likely to be ancestors of
plants because of their difference in pigmentation
B．The instability of freshwater habitats caused marine algae to
develop adaptations to their harsh environment.
C. The colonization of land by plants was a major revolution in
the history of Earth.
D. Terrestrial plants adjusted to life on land by undergoing
structural changes that enabled them to support themselves, resist
drying and exchange gases.
E. To colonize new terrestrial habitats, plants needed to create
a way of reproducing without water.
F. Once plants had overcome the challenges posed by terrestrial
life, they prospered by becoming less diverse.
