Self-study
P1
The characteristic smell or taste of a plant, to insects as well as to humans, depends on its chemical composition. ███████ █████████ ██████ ███████ ███ ██████████ ██ ████████ ███████████ ███████ ███ ██████████ ███
Intro topic ·
Two kinds of chemicals in plants: primary and secondary
Chemicals determine smell and taste of plants to insects and humans.
Primary substances ·
Stuff required for growth and functioning; found in all plants
Secondary substances ·
No known role in growth/functioning; give plants distinctive tastes and smells
P2
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Origin of secondary substances ·
Insects played major role
Causal mechanism 1 ·
Insects like some scents over others
Secondary substances result from mutations. Insects prefer some scents over others, which means the substances that produce those preferred scents are more likely to be passed on to future generations.
Causal mechanism 2 ·
Some substances produce stuff that helps defend against insects
Causal mechanism 3 ·
Some substances produce stuff that warns insects not to eat the plant
P3
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Competition between insects and plants ·
Insects evolve to respond to plants' defenses
Might evolve way to detoxify plant's poison or store the poison in an unharmful way, for example. Might evolve way to identify poisonous plants.
Passage Style
Phenomenon-hypothesis (RC)
Single position
8.
Which one of the following ████ ██████████ █████████ ███ ████ █████ ██ ███ ████████
a
Although the secondary ██████████ ██ ██████ ██ ███ ████ ████ ██ ███ ███████ █████ ██████████ ██████████ █████ ██████████ ███████ ██ ███████ ████████ ███████ ██████ ███ ███████████ ██ ████████
This is both too narrow and not supported. It’s too narrow, because it doesn’t capture the author’s claim that insects play a role in the development of secondary substances. It’s not supported, because
b
Long-term competition between ██████ ███ ███████ ███ ███ ██ █ █████████ ██ ███ █████ ██ █████████ ██████████ ███████ ██ ██████ ████ █████ ████ ██ █ █████████ ██ ███ █████ ██ ██████ ███████ ████ ███ ████ ███████ ██ ██████
This is both too narrow and not supported. It’s too narrow, because it doesn’t capture the author’s claim that insects play a role in the development of secondary substances. It’s not supported because the author never suggests that the range of secondary substances present in plants has narrowed, nor does she suggest that the range of insect species that eat each species of plant has narrowed. Rather, she states that the
c
The particular secondary ██████████ █████████ ██ █████████ ███████ ███ ████ ███ ███████████ ██████ ███ ██████ ████ ███████████ ██████ █████ ██████ ██ █████ ████ ████ ██ ████████████ ███████ ██ ███████████ ███████ ██████ ███ ████████
This best captures the main point, which is that
d
Due to long-term ████████████ █████████ ███████ ██ ████████ ███ █████████ ██████████ ██ ██████ ████ ██████ ████████ ███ ███████ ███ ████ ██ ██ ███████ █████ ███████ ███████ ████████
This isn’t supported, because the author never suggests that the evolutionary pressures of insects have caused the secondary substances in plants to be similar among closely related species. Although the author does acknowledge that the substances are similar in closely related species, and the author does believe insects’ evolutionary pressure contributes to secondary substances, she never connects the evolutionary pressure of insects to the similarity of secondary substances. In addition, even if she had, the focus of the passage isn’t on what contributed to the similarity of substances, but rather the general role that insects play in the development of secondary substances.
e
Because plant mutations ████ ███ ██ ███ ███████████ ██ █████████ ███████████ ██████ ████ ████ ██ ███████████ ██ █ ██████████ ███████ ██ ███████████ ████ ████████████ ████████
This doesn’t capture the author’s belief that insects have contributed to the development of secondary substances in plants. The mere assertion that plants compete with insects doesn’t contain the idea that insects have played a role in how secondary substances have developed.