問題詳情

Questions 40-50Pheromones are substances that serve as chemical signals between members of thesame species. They are secreted to the outside of the body and cause other individualsof the species to have specific reactions. Pheromones, which are sometimes calledLine "social hormones," affect a group of individuals somewhat like hormones do an individual(5) animal. Pheromones are the predominant medium of communication among insects(but rarely the sole method). Some species have simple pheromone systems and produceonly a few pheromones, but others produce many with various functions. Pheromonesystems are the most complex in some of the so-called social insects, insects that livein organized groups.(10) Chemical communication differs from that by sight or sound in several ways.Transmission is relatively slow (the chemical signals are usually airborne), but thesignal can be persistent, depending upon the volatility of the chemical, and is sometimeseffective over a very long range. Localization of the signal is generally poorer thanlocalization of a sound or visual stimulus and is usually effected by the animal's moving(15) upwind in response to the stimulus. The ability to modulate a chemical signal is limited,compared with communication by visual or acoustic means, but some pheromones mayconvey different meanings and consequently result in different behavioral or physiologicalresponses, depending on their concentration or when presented in combination. Themodulation of chemical signals occurs via the elaboration of the number of exocrine(20) glands that produce pheromones. Some species, such as ants, seem to be very articulatecreatures, but their medium of communication is difficult for humans to study andappreciate because of our own olfactory, insensitivity and the technological difficultiesin detecting and analyzing these pheromones.Pheromones play numerous roles in the activities of insects. They may act as alarm(25) substances, play a role in individual and group recognition, serve as attractants betweensexes, mediate the formation of aggregations, identify foraging trails, and be involved incaste determination. For example, pheromones involved in caste determination includethe "queen substance" produced by queen honey bees. Aphids, which are particularlyvulnerable to predators because of their gregarious habits and sedentary nature, secretean alarm pheromone when attacked that causes nearby aphids to respond by moving away.
40. What does the passage mainly discuss?
(A) How insects use pheromones to communicate
(B) How pheromones are produced by insects
(C) Why analyzing insect pheromones is difficult
(D) The different uses of pheromones among various insect species

參考答案

答案：D
難度：非常困難0
統計：A(0),B(0),C(0),D(0),E(0)

內容推薦

內容推薦