Arthropods

Arthropods

1. are insects

2. Contain:

   • Chitnous Exoskeleton
     • Exoskeletons provide:
       • Protection, sensing, feeding, barrier against desiccation, defense from predators, support, provide a framework for musculature
     • Benefits of an exoskeleton
       • be repaird
       • Durable, yet flexible and gas permeable
       • easily modified in color, or shape for adaptation
     • Exoskeleton Limitations
       • Rigidity limits growth, requiring molting
   • Segmented Body
     • Evolution of segmented body
       • during evolution of arthropods, segments have become reduced in number and specialized with some independece from each other
     • Benefits of segments
       • Modules are units that are connected bt have a lot of indepence
         • allows flexibility in any system
   • Jointed legs
     • Benefits
       • Flexibility, strength, agility, improve mobility in terrestrial environments
   • Nervous System
     • One pair of gangilia per segment
   • Open circulatory System
     • blood and other fluids move in an internal space

3. 5 main groups

   • Trilobites
     • Three main body parts: Head, thorax, tail
     • Marine
     • Curled up for protection
     • Disappeared at the end of Permian 272
   • Myriapoda
     • Variable number of legs
     • Segmented and legs added with each molt
       • Mandibular mouth parts
         • Reproduction through external transfer of sperm
           • Entirely terrestrial
     • Two classes
       • Chilopada
         • Centipedes
           • 1 pair of appendages per segment
             • Predatory with venom
       • Diplopada
         • Millipedes
           • 2 pairs appendages per segment
             • Generally detritivores
   • Arachnids
     • Includes scorpions, spiders, mites, ticks
       • two main body parts
         • abdomen and cephalothorax
         • 8 legs
           • mouth parts contain chilcerae rather than mandibles
             • No antennae or wings
               • terrestrial
   • Crustaceans
     • primarily marine
       • Appendages are typically biramous
     • Three body parts:
       • head
       • Thorax
       • abdomen
       • two pairs of antennae
   • Insects
     • 6 legs
       • appendages uniramous
         • 3 body parts
           • head
           • thorax
           • adbomen
           • winged at adult stage
             • single pair of antennae
               • diverged from crustacea about 440 mya
     • divided into 3 groups
       • Entognatha
         • small wingless soil arthropods
       • Parainsecta
         • other small wingless arthropods
       • Insecta
     • success
       • largest numbr of individuals of any class of animals
         • colonize all habitats
           • low extinction rates
             • diverse
               • provide essential ecosystem function
                 • large abundane:1/3 of all animal biomass
                   • Diversity of insects
                     • 28 different orders
                       • Most divers occurs in 5 orders
                         • Hemiptera
                           • True bugs
                         • Diptera
                           • flies
                         • Hymenoptera
                           • wasps, ants, bees
                         • Lepidoptera
                           • butterflies and moths
                         • Coleoptra
                           • bettles
                     • so diverse because they were the first to fly
                       • flight allows dispersal
                       • Opens wide ranges of ecological niches
                       • Find mates
       • First to adapt and diverse on land
         • first colonizing
           • exoskeletons
             • small body size
               • allows grater diversity and abunance of ecological niches
               • short generation times
             • protect internal organs from harsh enviroments and modifed system for beating on land
     • have specialized development processes
       • Hemimetaboly
         • egg. several myph stages, adult
       • Holometaboly
         • egg, several larval stages, pupa, adult
           • advantages
             • immatures and adults are specialized for different functions
             • Immatures and adults dont compate for resources
         • More diversity