1
|
According to paragraph 1,
how the slime mold should be classified used to be
|
→Cellular slime molds are
extraordinary life forms that exhibit features of both fungi and protozoa,
although often classed for convenience with fungi. At one time they were
regarded as organisms of ambiguous taxonomic status, but more recent
analysis of DNA sequences has shown that slime molds should be regarded as
inhabiting their own separate kingdom. Their uniqueness lies in their
unusual life cycle, which alternates between a feeding stage in which the
organism is essentially unicellular and a reproductive stage in which the
organism adopts a multicellular structure. At the first stage they are
free-living, separate amoebae, usually inhabiting the forest floor and
ingesting bacteria found in rotting wood, dung, or damp soil. But their
food supplies are relatively easily exhausted since the cells' movements
are restricted and their food requirements rather large.
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A
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unknown
|
B
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uncertain
|
C
|
controversial
|
D
|
unfamiliar
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Paragraph 1 is marked with an arrow [→]
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2
|
The word "ingesting"
in the passage is closest in meaning to
|
Cellular slime molds are extraordinary life forms that exhibit
features of both fungi and protozoa, although often classed for convenience
with fungi. At one time they were regarded as organisms of ambiguous
taxonomic status, but more recent analysis of DNA sequences has shown that
slime molds should be regarded as inhabiting their own separate kingdom.
Their uniqueness lies in their unusual life cycle, which alternates between
a feeding stage in which the organism is essentially unicellular and a
reproductive stage in which the organism adopts a multicellular structure.
At the first stage they are free-living, separate amoebae, usually
inhabiting the forest floor and ingesting bacteria found in rotting wood, dung, or damp
soil. But their food supplies are relatively easily exhausted since the
cells' movements are restricted and their food requirements rather large.
|
A
|
chewing
|
B
|
catching
|
C
|
absorbing
|
D
|
consuming
|
|
3
|
According to the passage, what is unusual about the slime molds'
life cycle?
|
[Refer to the full passage.]
|
A
|
They inhabit their own kingdom.
|
B
|
They are organisms whose classification is ambiguous.
|
C
|
They alternate between unicellular and multicellular
structures.
|
D
|
They are free-living organisms.
|
|
4
|
According to the passage, what is the primary reason the cells need
to combine into a single larger creature?
|
[Refer to the full passage.]
|
A
|
To move to find a new food source
|
B
|
To slow the rate of ingesting food
|
C
|
To become separate creatures
|
D
|
To create their own kingdom
|
|
5
|
Look at the four squares [■] that indicate where the following sentence could be
added to the passage.
Starvation is reached when the population of cells is high in
relation to the abundance of the food source.
Where would the sentence best fit?
Choose the letter of the square that shows where the sentence should
be added.
|
When the cells become starved of nutrition, the organism initiates a
new genetic program that permits the cells to eventually find a new,
food-rich environment. [A]
At this point, the single-celled amoebae combine together to form what will
eventually become a multicellular creature. [B] The mechanism by which the individual
members become a single entity is essentially chemical in nature. [C] At first, a few
of the amoebae start to produce periodic chemical pulses that are detected,
amplified, and relayed to the surrounding members, which then move toward
the pulse origin. [D]
In time, these cells form many streams of cells, which then come together
to form a single hemispherical mass. This mass sticks together through the
secretion of adhesion molecules.
|
O
|
A
|
O
|
B
|
O
|
C
|
O
|
D
|
|
6
|
The word "entity"
in the passage is closest in meaning to
|
When the cells become starved of nutrition, the organism initiates a
new genetic program that permits the cells to eventually find a new,
food-rich environment. At this point, the single-celled amoebae combine
together to form what will eventually become a multicellular creature. The
mechanism by which the individual members become a single entity is essentially
chemical in nature. At first, a few of the amoebae start to produce
periodic chemical pulses that are detected, amplified, and relayed to the
surrounding members, which then move toward the pulse origin. In time,
these cells form many streams of cells, which then come together to form a
single hemispherical mass. This mass sticks together through the secretion
of adhesion molecules.
|
A
|
division
|
B
|
species
|
C
|
piece
|
D
|
unit
|
|
7
|
The word "others"
in the passage refers to
|
The mass now develops a tip, which elongates into a finger-like
structure of about 1 or 2 millimeters in length. This structure eventually
falls over to form a miniature slug, moving as a single entity orienting
itself toward light. During this period the cells within the mass
differentiate into two distinct kinds of cell. Some become prestalk cells,
which later form into a vertical stalk, and others form prespore cells, which become the
spore head.
|
A
|
cells
|
B
|
stalks
|
C
|
spores
|
D
|
kinds
|
|
8
|
All of the following are mentioned in paragraph 4 as being parts of
the multicellular slug EXCEPT
|
→ As the organism migrates, it leaves
behind a track of slime rather like a garden slug. Once a favorable
location has been found with a fresh source of bacteria to feed on, the
migration stops and the colony metamorphoses into a fungus-like organism in
a process known as "culmination." The front cells turn into a
stalk, and the back cells climb up the stalk and form a spherical-shaped
head, known as the sorocarp. This final fruiting body is about 2
millimeters in height The head develops into spores, which are dispersed
into the environment and form the next generation of amoebae cells. Then
the life cycle is repeated. Usually the stalk disappears once the spores
have been released.
|
A
|
the head
|
B
|
the stalk
|
C
|
legs
|
D
|
spores
|
Paragraph 4 is marked with an arrow [→].
|
9
|
In paragraph 4, why does the author refer to the fungus-like
organism as a fruiting body?
|
→ As the organism migrates, it leaves
behind a track of slime rather like a garden slug. Once a favorable
location has been found with a fresh source of bacteria to feed on. the
migration stops and the colony metamorphoses into a fungus-like organism in
a process known as "culmination." The front cells turn into a
stalk, and the back cells climb up the stalk and form a spherical-shaped
head, known as the sorocarp. This final fruiting body is about 2
millimeters in height. The head develops into spores, which are dispersed
into the environment and form the next generation of amoebae cells. Then
the life cycle is repeated. Usually the stalk disappears once the spores
have been released.
|
A
|
Because it has become one entity
|
B
|
Because it is 2 millimeters in height
|
C
|
Because it now has a stalk and head
|
D
|
Because it has reached its reproductive stage
|
Paragraph 4 is marked with an arrow [->].
|
10
|
Which of the sentences below best expresses the essential
information in the highlighted sentence? Incorrect choices change the
meaning in important ways or leave out essential information.
|
As the organism migrates, it leaves behind a track of slime rather
like a garden slug. Once a favorable location has been found with a fresh
source of bacteria to feed on, the migration stops and the colony
metamorphoses into a fungus-like organism in a process known as
"culmination." The front cells turn into a stalk, and the back
cells climb up the stalk and form a spherical-shaped head, known as the
sorocarp. This final fruiting body is about 2 millimeters in height. The head develops into
spores, which are dispersed into the environment and form the next
generation of amoebae cells. Then the life cycle is repeated.
Usually the stalk disappears once the spores have been released.
|
A
|
The next generation of amoebae cells disperses into
the environment by attaching themselves to spores on the head.
|
B
|
After the spores that form the head are scattered around the area,
they develop into a new generation of amoebae cells.
|
C
|
The spores develop into amoebae cells and then become
spread around the head of the slug.
|
D
|
The spores spread throughout an area and develop into a new
generation of amoebae cells.
|
|
11
|
It can be inferred that developmental biologists are especially
interested in the slime mold because
|
[Refer to the full passage.]
|
A
|
the change in degree of specialization in its cells
helps them to understand cell development in more complex organisms
|
B
|
it is convenient to perform experiments on a creature that is
composed of two different cell types
|
C
|
scientists could form hybrid organisms in their
experiments using the same process that slime mold uses to transform itself
|
D
|
it is easy to find specimens on which to perform experiments
|
|
12
|
According to the passage, the recent DNA studies
|
[Refer to the full passage.]
|
A
|
give similar results to the dye studies
|
B
|
contradict the dye studies
|
C
|
are less exact than the dye studies
|
D
|
have introduced confusion about the dye study results
|
|
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