Invertebrates lack the well- developed skeleton system, backbone, notochord as well nervous system whereas, Vertebrates constitutes, segmented, motile vertebral column together term as the spine, along with proper organized, nervous system, digestive system, gastrointestinal tract, respiratory system (which can be gills or lungs). All the animals present on earth are classified in two categories only, which are Invertebrates or Vertebrates. Though it is said that Vertebrates arose from … [Read more...]