Resin is a plant secretion that hardens when exposed to air; fossilized resin is called amber. Although Pliny in the first century recognized that amber was produced from "marrow discharged by trees," amber has been widely misunderstood to be a semiprecious gem and has even been described in mineralogy textbooks. Confusion also persists surrounding the term "resin," which was defined before rigorous chemical analyses were available. Resin is often confused with gum, a substance produced in plants in response to bacterial infections, and with sap, an aqueous solution transported through certain plant tissues. Resin differs from both gum and sap in that scientists have not determined a physiological function for resin.

In the 1950s, entomologists posited that resin may function to repel or attract insects. Fraenkel conjectured that plants initially produced resin in nonspecific chemical responses to insect attack and that, over time, plants evolved that produced resin with specific repellent effects. But some insect species, he noted, might overcome the repellent effects, actually becoming attracted to the resin. This might induce the insects to feed on those plants or aid them in securing a breeding site. Later researchers suggested that resin mediates the complex interdependence, or "coevolution," of plants and insects over time. Such ideas led to the development of the specialized discipline of chemical ecology, which is concerned with the role of plant chemicals in interactions with other organisms and with the evolution and ecology of plant antiherbivore chemistry (plants' chemical defenses against attack by herbivores such as insects).

467) According to the passage, which of the following is true of plant antiherbivore chemistry?
(A) Changes in a plant's antiherbivore chemistry may affect insect feeding behavior.
(B) A plant's repellent effects often involve interactions between gum and resin.
(C) A plant's antiherbivore responses assist in combating bacterial infections.
(D) Plant antiherbivore chemistry plays only a minor role in the coevolution of plants and insects.
(E) Researchers first studied repellent effects in plants beginning in the 1950s.

468) Of the following topics, which would be most likely to be studied within the discipline of chemical ecology as it is described in the passage?
(A) Seeds that become attached to certain insects, which in turn carry away the seeds and aid in the reproductive cycle of the plant species in question
(B) An insect species that feeds on weeds detrimental to crop health and yield, and how these insects might aid in agricultural production
(C) The effects of deforestation on the life cycles of subtropical carnivorous plants and the insect species on which the plants feed
(D) The growth patterns of a particular species of plant that has proved remarkably resistant to herbicides
(E) Insects that develop a tolerance for feeding on a plant that had previously been toxic to them, and the resultant changes within that plant species

469) The author refers to "bacterial infections" (see line 11) most likely in order to
(A) describe the physiological function that gum performs in plants
(B) demonstrate that sap is not the only substance that is transported through a plant's tissues
(C) explain how modern chemical analysis has been used to clarify the function of resin
(D) show that gum cannot serve as an effective defense against herbivores
(E) give an example of how confusion has arisen with regard to the nature of resin

470) The author of the passage refers to Pliny most probably in order to
(A) give an example of how the nature of amber has been misunderstood in the past
(B) show that confusion about amber has long been more pervasive than confusion about resin
(C) make note of the first known reference to amber as a semiprecious gem
(D) point out an exception to a generalization about the history of people's understanding of amber
(E) demonstrate that Pliny believed amber to be a mineral

Q467: A
Q468: E
Q469: A
Q470: D