Essay about Reptiles: Reptiles oviparous M.

Reptiles A.) External Structure Reptiles are tetrapod vertebrates, creatures that either have four limbs or, like snakes, being descended from fourlimbed ancestors.
Reptilian skin is covered in a horny epidermis, making it watertight and enabling reptiles to live on dry land, in contrast to amphibians.
reptiles skin is rather thin and lacks the thick dermal layer that produces leather in mammals
Exposed parts of reptiles are protected by scales or scutes, sometimes with a bony base, forming armor
B.)Locomotion.)
Crocodiles and alligators, turtles, most lizards, and tuataras can walk on their four legs.
Although not all reptiles have legs, many of them do.
Usually they walk with their legs held out from the body, rather like a human would hold up his or her body when doing a pushup.
Many of the smaller lizards, in particular, are very speedy, zipping across the ground at speeds that make their capture difficult.
C.) Nutriton and Digestive System
Most reptiles are insectivorous or carnivorous and have rather simple and comparatively short digestive tracts, meat being fairly simple to break down and digest
Digestion is slower than in mammals, reflecting their lower resting metabolism and their inability to divide and masticate their food
Some reptiles have sticky tongues for capturing prey
the glottis is far forward so that the snake can breathe while slowing its prey
D.) Gas Exchange and circulatory system
Reptiles exchange respiratory gases across internal respiratory surfaces to avoid losing large amounts of water
lung chambers provide a large surface area for gas exchange
reptiles possess two atria that are completely separated in the adult and has veins from the body and lungs emptying into them
they stop breathing during diving.
E.) Temperature Regulation
the ventricle of most reptiles is completely divided
the ventral aorta and conus arteriosclerosis divide during development and become three major arteries that leave the heart
blood low in oxygen enters the ventricle from the lungs via pulmonary veins
F.) Nervous and Sensory Functions
The cerebral hemispheres are somewhat larger than those of amphibians
The increased size is associated with an improved sense of smell
the optic lobes and cerebellum are also enlarged which reflects increased reliance on vision and more coordinated muscle functions
the ears of snakes detect substrate vibrations
G.)Excretion and Osmoregulation

most reptiles excrete Uric acid
the kidneys are similar to fishes and amphibians
the urinary bladder or cloacal walls reabsorb water and Uric acid can be stored

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