Insects[1] - Hexapoda “The little things that run the world” How did the hexapod body plan evolve • Multi-legged ancestor • More efficient

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Unformatted text preview: Hexapoda “The little things that run the world” How did the hexapod body plan evolve? • Multi-legged ancestor • More efficient locomotion • Body supported by two tripods Insects evolved from many-legged ancestors. ? Current information favors the Crustacea as the sister group Of insects. Maybe insects are crustaceans! Today’s jumping bristletails still have rudimentary appendages on their abdominal segments and leg-like mouthparts. • No wings • Adapted as a mobile ground dweller This pattern supports the views that mouthparts are modified legs and that hexapods evolved by loss or reduction of abdominal legs. Today’s jumping bristletails still have rudimentary appendages on their abdominal segments and leg-like mouthparts. • No wings • Adapted as a mobile ground dweller This pattern supports the views that mouthparts are modified legs and that hexapods evolved by loss or reduction of abdominal legs. Early Hexapods (Insects) Evolution of Wings • Exaptation • Possible sources: lobes on thorax Gills from biramous ancestor • Previous function: Gliding Thermoregulation Respiration Wing Diversity • Membranous • Forewing hardened for protection • Wings coupled together • Hindwing reduced or lost • Muscle and nervous system adaptations Membranous Wings Both wings involved in powered flight Hardened Protective Forewings Beetles, Cockroaches, etc Hindwing dominates in flight Coupling Wings Together with Velcro- like Hooks or Coupling Wings Together with a Long Spine Hindwing Reduced or Lost • Best example-flies • Hindwing becomes balancing organ Growth and Metamorphosis...
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This note was uploaded on 09/23/2011 for the course BIOL 240 taught by Professor Staff during the Spring '11 term at S.F. State.

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Insects[1] - Hexapoda “The little things that run the world” How did the hexapod body plan evolve • Multi-legged ancestor • More efficient

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