PrepTest 75, Section 3, Question 6
If newly hatched tobacco hornworms in nature first feed on plants from the nightshade family, they will not eat leaves from any other plants thereafter. However, tobacco hornworms will feed on other sorts of plants if they feed on plants other than nightshades just after hatching. To explain this behavior, scientists hypothesize that when a hornworm's first meal is from a nightshade, its taste receptors become habituated to the chemical indioside D, which is found only in nightshades, and after this habituation nothing without indioside D tastes good.
If newly hatched tobacco hornworms in nature first feed on plants from the nightshade family, they will not eat leaves from any other plants thereafter. However, tobacco hornworms will feed on other sorts of plants if they feed on plants other than nightshades just after hatching. To explain this behavior, scientists hypothesize that when a hornworm's first meal is from a nightshade, its taste receptors become habituated to the chemical indioside D, which is found only in nightshades, and after this habituation nothing without indioside D tastes good.
If newly hatched tobacco hornworms in nature first feed on plants from the nightshade family, they will not eat leaves from any other plants thereafter. However, tobacco hornworms will feed on other sorts of plants if they feed on plants other than nightshades just after hatching. To explain this behavior, scientists hypothesize that when a hornworm's first meal is from a nightshade, its taste receptors become habituated to the chemical indioside D, which is found only in nightshades, and after this habituation nothing without indioside D tastes good.
If newly hatched tobacco hornworms in nature first feed on plants from the nightshade family, they will not eat leaves from any other plants thereafter. However, tobacco hornworms will feed on other sorts of plants if they feed on plants other than nightshades just after hatching. To explain this behavior, scientists hypothesize that when a hornworm's first meal is from a nightshade, its taste receptors become habituated to the chemical indioside D, which is found only in nightshades, and after this habituation nothing without indioside D tastes good.
Which one of the following, if true, adds the most support for the hypothesis?
Tobacco hornworms that first fed on nightshade leaves show no preference for any one variety of nightshade plant over any other.
If taste receptors are removed from tobacco hornworms that first fed on nightshade leaves, those hornworms will subsequently feed on other leaves.
Tobacco hornworm eggs are most commonly laid on nightshade plants.
Indioside D is not the only chemical that occurs only in nightshade plants.
The taste receptors of the tobacco hornworm have physiological reactions to several naturally occurring chemicals.
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