Within the phylum Chordate, all species will feature the following in at least one stage in its life:
- 96% of all chordates are vertebrates - have a vertebral column
- spinal chord - the hollow dorsal nerve chord in vertebrates - vertebrae - individual segments of a notochord that enclose and protect spinal chord - reproduction: - oviparous - embryos develop in eggs and hatch outside of mother's body - oviviviparous - eggs stay within mother's body after internal fertilization - most mammals - viviparous - embryos develop inside mother's body (no egg developed) - four structures of the amniotic egg are most vital to advanced chordate's adaptation to the terrestrial environment 1. amnion - cusion for embryo 2. yolk sac - regulates gas-content between membranes 3. chorion - protein to help embryo develop 4. allantois - stores waste from embryo |
Evolution between the Classes of Chordata |
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+ notochord
+ nerve chord + pharyngeal pouches + tail + gas exchange + closed circulatory system + paired fins = control
+ scales = protection + gills + jaws + lateral line system + swim bladder = gas storage + kidney + liver & pancreas + pyloric cecum - secretes digestive enzymes & absorbs nutrients + complex, 1-directional 4-part heart + lungs
- scales + pelvic girdle - weight support + gall bladder + timpanic membrane - eardrums + nictilating membrane - protect & moisten eyeballs + double-loop circulatory system + cloaca + scales = protection & water conserv.
+ earbones = conduct sound + spongy lungs = better gas exchange + leathery amniotic eggs = water conservation + crystallized uric acid (waste) = water conservation + feathers
+ endothermic + beaks adapted to diet + crop & gizzard = may regurgitate food for young - teeth + teeth
+ hair + mammary glands |
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http://animaldiversity.ummz.umich.edu/accounts/Mammalia/