Arthropods

Arthropods

1. 80% OF ALL KNOWN SPECIES ARE ARTHROPODS!

   • this group flourishes because of their segmented bodies
     • evolved, the segments became more specialised, leading to diversity in group
       • really diverse group! including such as
         • scorpions!
           • butterflies!
             • lobsters!
               • all arthropods have segmented bodies!
                 • in most cases that means head, thorax, abdomen- three segments
                   • all arthropods have an exoskeleton!
                     • exoskeleton is made out of chitin
                       • all arthropods have paired and jointed appendages!
                         • arthropod means jointed feet
                           • arthropods have all this in common! but!
                             • arthropods are grouped into four! subphyla based on how they differ
                               • includes spiders and scorpions and horseshoe crabs!
                                 • 1. cheliceriformes
                                   • largest class of cheliceriformes are the arachnids
                                 • cheliceriformes: greek for 'arm lips'
                                   • simple, non compound eyes
                                     • lack anntenae
                                       • most live on land
                               • 2. myriapoda: 'many feet'
                                 • includes millipedes and centipedes
                                   • many legs
                                 • 3.hexipoda: '6 feet'

2. segmentation as an indicator of complexity

   • all segmented animals have a common ancestor;
     • three common groups have segmentation
   • annelida is one of the earliest to display segmentation
     • annelida latin for 'little rings' (segmentation
     • segmentation is an example of synapomorphy in annelids
       • synapomorphy
     • annelida have chaetae
       • chaetae are little bristles on body that provide traction
         • you can learn about animal's lineage through its synapomorphy and plesiomorphies
           • plesiomorphies

3. ANNELIDA

   • 1. oligochaetes: earth worms: meaning few chaetae
     • 2. hirudinea: LEECHES!, many parasitic
       • 3. polychaetes: bristly worms, many chaetes!
         • almost all of these are marine species