Reptiles Body Plan • Contrary to common belief, reptile scales can be smooth or rough, and they are never slimy. • The basic reptilian body plan includes a well developed skull, a backbone and tail, two limb girdles, and four limbs. • The only two reptiles that do not follow this plan are turtles (which have a hard shell fused to their vertebrae) and snakes (which have no limbs). • Reptiles are “heated from the outside.” Because of this, they are called ectotherms and they lack effective insulation so they need to gain additional heat by laying in the sun. • Skeletal
Feeding • Some reptiles are herbivores while others are carnivores. • The way reptiles get their prey vary. Some snakes paralyze with a powerful venom while others suffocate their prey by wrapping tightly around them.
Respiration and Internal Transport • Since gasses are unable to diffuse easily across the scaly skin of reptiles, all reptiles have well-developed lungs, to help in this area. • To help with this area also, reptiles have muscles attached to their rib cage to enable their lungs to inflate and deflate. Diagram • Additionally, reptiles have a double-loop circulatory system to allow the blood to first pass through the lungs and then to the remainder of the body. Diagram • Although there are exceptions, most reptiles have a “not quite four-chambered heart because the oxygenated and deoxygenated blood mix in a few areas.
Excretion • Reptiles that live primarily in the water (like alligators and crocodiles) excrete most of their nitrogenous wastes in the form of ammonia. • Many other reptiles covert their waste into uric acid. • The excretion of uric acid presents two benefits over ammonia: • 1. Uric acid is less toxic. • 2. It is not soluble in water. • As a result, reptiles with uric acid excretion are better able to conserve water because the urine flows into an organ called the cloaca, where crystals of uric acid form a semisolid paste. By getting rid of these dry wastes, water is able to be conserved. Diagram
Nervous System and Sense Organs • Reptiles have brains similar to Amphibians, except reptiles have a bigger cerebrum and cerebellum. • Reptiles have really good vision. • According to the Biology textbook, most snakes probably see more colors than you do!
Movement • Reptiles have large and strong legs that easily support their body weight. • Their strong limbs allow for many actions to be performed, including running, swimming, burrowing, and climbing.
Reproduction • Reptiles are the first vertebrates to live without relying on water. • This is because their eggs are fertilized internally, and then develop into an amniotic egg meaning an embryo surrounded by a leathery external shell.
Works Cited • Turtle diagrams: • http://www.bio.davidson.edu/Courses/anphys/2000/Pleasants/resp.htm • http://www.bio.davidson.edu/Courses/anphys/2000/Pleasants/circ.htm • All pictures are from clipart!