Insect Wings

Insect WingsThe power of flight is a major chapter in the success story of insects. Becauseinsects with developed wings appear relatively suddenly in the fossil recordand there are no good fossils that show intermediate stages, there is a greatdeal of speculation as to how wings might have evolved.Insects are different from other flying creatures like birds and bats, whichevolved wings from already existing legs, and one of the main questions iswhat the first protowings (early forms of wings) were used for.00 One view isthat outgrowths from the notum (upper portion) of the thorax (middle region ofthe body between the head and the abdomen) would have enabled insects tohave a more stable and longer glide path (movement through the air withoutusing wings). 00 This paranotal theory envisages early insects climbing plantsand launching themselves into the air as a more efficient, and perhaps safer,means of getting around or avoiding predators. 00 These protowings mighthave had other functions, and experimental evidence suggests that whensmall, they would have had a significant role in the regulation of bodytemperature. 00 Other ideas have involved small insects being carried aroundin air currents or larger insects jumping from the ground and taking to the air.According to paragraph 2, one benefit of the outgrowths from an insect'sthorax might have been toA.allow the insect to sense the presence of predatorsB.prevent the insect from being carried away by air currentsC.allow the insect to glide through the air for a longer distanceD.aid the insect in climbing up plantsLook at the four squares [▇] that indicate where the following sentence couldbe added to the passage. Where would the sentence best fit?The research showed that protowings less than 1.3 centimeters longwould have helped insects absorb heat from sunlight.There is a major problem with ideas that involve paranotal protowings and gliding, whichis that, at some time, these fixed structures needed to have become hinged (connected ina way that allows on structure to swing relative to the other) and to have developedmuscle systems to make them flap up and down. It is much easier to imagine structuresthat were already hinged and muscled in fulfilling some prior function and then eventuallytaking on a role in flight. The endite-exite theory suggests that protowings developed fromthe fusion of inner and outer appendages (endites and exites) of short leg segments,which were already hinged and might have been under some sort of muscular control.An additional convincing argument in support of the theory that wings developed from legappendages, and that further disputes the paranotal theory, comes from the occurrenceand distribution of sensory receptors on the wings of today’s insects. Chemical-sensingorgans are not found on the surface of the thorax but are typical of legs. Furthermor...