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- Wed May 17, 2017 2:10 pm
#34967
Passage Discussion
Paragraph One:
In the first paragraph, the author introduces two categories of chemical substances in plants—
primary and secondary. The distinction is a crucial one: primary substances are essential for growth
and are found in all plants, whereas secondary substances give plants their distinctive tastes and
smells, but play no metabolic role. As such, secondary substances are diverse but tend to be similar
among closely related species of plants. Both definitions should be highlighted and notated, as they
are likely to provide a much-needed reference point later on.
Paragraph Two:
The second paragraph describes the evolutionary pressures exerted by insects, as a result of which
certain secondary substances in plants are favored by natural selection (the first sentence contains
the main point of the passage, and should be highlighted). Note that secondary substances appear
as a result of random genetic mutations. Insects, however, influence which particular substances
are passed on to subsequent generations of the plant species: some chemicals are favored by natural
selection because their scent attracts pollinating insects, while others are passed on because they
operate as natural defenses against damage and destruction by insects. Remembering each example
is probably not as important (or as realistic) as notating them (e.g. “Ex. 1,” “Ex. 2,” etc.).
Paragraph Three:
The third paragraph elaborates on the evolutionary competition for advantage between plants and
insects. Here, the focus is on insects. As plants develop defenses against certain insects, the insects
evolve ways of circumventing these defenses. As a result, fewer and fewer plants remain suitable as
food sources for any one species of insect.
VIEWSTAMP Analysis
There is only one Viewpoint expressed in the passage: that of the author’s.
The general Structure of the passage is as follows:
Paragraph 1: Explain what secondary substances are, and distinguish them from primary
substances.
Paragraph 2: Describe how the evolutionary pressures exerted by insects lead to particular
secondary substances in plants being favored by natural selection.
Paragraph 3: Elaborate on the evolutionary competition for advantage between plants
and insects and describe how insects adapt to circumvent plants’ chemical
defenses.
The author’s Tone is more scholarly than polemic. The passage could have easily been drawn from
an introductory textbook on plant biology.
The primary Argument in the passage is that of the author, who asserts that insects have played a
major role in determining which secondary substances in plants are favored by natural selection. This
claim is supported by several examples, and an implication of it is presented in the third paragraph.
The author’s Main Point is to describe what secondary substances in plants are, argue that some of
them are favored by natural selection, and explain the role of insects in this process.
Paragraph One:
In the first paragraph, the author introduces two categories of chemical substances in plants—
primary and secondary. The distinction is a crucial one: primary substances are essential for growth
and are found in all plants, whereas secondary substances give plants their distinctive tastes and
smells, but play no metabolic role. As such, secondary substances are diverse but tend to be similar
among closely related species of plants. Both definitions should be highlighted and notated, as they
are likely to provide a much-needed reference point later on.
Paragraph Two:
The second paragraph describes the evolutionary pressures exerted by insects, as a result of which
certain secondary substances in plants are favored by natural selection (the first sentence contains
the main point of the passage, and should be highlighted). Note that secondary substances appear
as a result of random genetic mutations. Insects, however, influence which particular substances
are passed on to subsequent generations of the plant species: some chemicals are favored by natural
selection because their scent attracts pollinating insects, while others are passed on because they
operate as natural defenses against damage and destruction by insects. Remembering each example
is probably not as important (or as realistic) as notating them (e.g. “Ex. 1,” “Ex. 2,” etc.).
Paragraph Three:
The third paragraph elaborates on the evolutionary competition for advantage between plants and
insects. Here, the focus is on insects. As plants develop defenses against certain insects, the insects
evolve ways of circumventing these defenses. As a result, fewer and fewer plants remain suitable as
food sources for any one species of insect.
VIEWSTAMP Analysis
There is only one Viewpoint expressed in the passage: that of the author’s.
The general Structure of the passage is as follows:
Paragraph 1: Explain what secondary substances are, and distinguish them from primary substances. Paragraph 2: Describe how the evolutionary pressures exerted by insects lead to particular secondary substances in plants being favored by natural selection. Paragraph 3: Elaborate on the evolutionary competition for advantage between plants and insects and describe how insects adapt to circumvent plants’ chemical defenses.The author’s Tone is more scholarly than polemic. The passage could have easily been drawn from
an introductory textbook on plant biology.
The primary Argument in the passage is that of the author, who asserts that insects have played a
major role in determining which secondary substances in plants are favored by natural selection. This
claim is supported by several examples, and an implication of it is presented in the third paragraph.
The author’s Main Point is to describe what secondary substances in plants are, argue that some of
them are favored by natural selection, and explain the role of insects in this process.