BI256 Study Guide - Venom Snake, Oviparity, Envenomation
Document Summary
Superclass tetrapoda: phylum chordata, clade amniota, class reptilia, order testudines, order squamata, order sphenodonta, order crocodilia. Cladogram of amniota (cid:224) based on # of openings in the skull: anapsid, diapsid, skull has no openings behind the orbit, skull has two temporal openings a. lepidosaurs (lizards,snakes,tuataras) b. archosaurs (dinosaurs*, pterosaurs*, crocodiles, birds) c. sauropterygians* d. ichthyosaurs* e. turtles, synapsid: one temporal opening, pelycosaurs, theraspids, mammals. Derived characters of amniotes: amniotic egg, thicker and more waterproof shin, rib ventilation of the lungs, stronger jaws, high pressure cardiovascular systems, water conserving nitrogen excretion, expanded brain and sensory organs. 4 membranes: amnion: encloses the embryo in fluid, providing an aquatic environment, allentois: stores nitrogenous wastes, chorion: acts in respiration (gas exchange), provides physical protection and prevents dessication, allentios and chorion sometime fuse to form a respiratory structure called the chorioallantoic membrane; both are highly vascularized, yolk sac: nutrient storage, shell: outer protective shell parchment, leathery or calcified.
