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
13.
The passage most strongly suggests ████ █████ ███ ██ ███ █████████ ██ ████ ██ █████████ ██████████ ██ ███████
a
Some of them ███ ███ ███████ ██ ██████ ███████ █████████ ██ ███████
b
They typically contribute ██ █ ███████ █████ ██ ██████ ███ ███ █████
The author never suggests that an individual secondary substance cannot contribute to both taste and smell.
c
Some of them ███████ ████████ █████████ ████ ██████████ ████████ ██ ████████ ████ ████████ ███ ███████ ████████ ████████████
The author never suggests the secondary substances undergo any chemical reaction with substances from insects.
d
Some species of ██████ ███████ ████ ███ ████ ██████████
Although “only a few” secondary substances occur in any one species of plant, we have no evidence some plants produce “only one” secondary substance.
e
A few of ████ ███ ██ ██████████ ██ ███████ ██████████ ██ ███████ ███████████
We have no evidence that some secondary substances play any role in the production of primary substances.