REPTILES: Reptile is a common name applied to the members of the Vertebrate class. This class includes snakes, lizards, turtles, crocodiles, and tuatara and other extinct species. Among all of the existing reptiles there are 2,500 species of snakes; 2,500 species of lizards; about 250 species of turtles; 22 species of crocodilians, and two species of tuataras. They are distributed throughout the temperate and tropical regions of the world.
Since reptiles are cold blooded they can not live in permanently cold places such as the Polar Regions. But there are several species that can be located in the north of the Arctic Circle. The majority of the reptiles are egg laying organisms that are known as oviparous. But many snakes and lizards are viviparous or give birth to living young. The eggs of reptiles have 4 specialized membranes: the amnion, the yolk sac, the allantois, and the chorion. The amnion surrounds the embryo and contains the amniotic fluid.
As the embryo develops, the allantois grows out from the embryo hindgut. The yolk-sac membranes cover the yolk, which is used as food for the growing embryo. The chorion surrounds the embryo and the other membranes. In most snakes and some lizard's only one lung works: in other reptiles, both lungs are equally developed. Reptiles are commonly called cold-blooded. But that is not really true.
I say this because some reptiles when they are active have bodies at a higher temperature than most other mammals. The difference is that reptiles rely on external or outer sources of heat. Where as birds and mammals use internal heat. Reptiles regulate their body temperature by getting their heat from the sun, warm stones, warm logs, and the heated earth. Usually the body temperature of the reptile is higher than the surrounding air. A snake is a common word for reptile belonging to the serpent family.
The body is elongated and usually cylindrical. Sea snakes and tree-dwelling snake have the body compressed laterally. Snakes lack external limbs, but some snakes such as boas and pythons are at the base of the tail. The body is covered with scales and a horny epidermal material arranged in rows and over lap each other, sort of like tiles on a roof.
The frequency of the shedding of the skin varies from snake to snake. Shedding occurs based on the age and species they are and the size of the individual is. Young rapid growing snakes shed more frequently than slow growing adults did. In some species the skin is shed every 20 days; and in others it is shed only once a year. The venom is a complex mixture of proteins that destroys certain types of tissues. Venom are classified in two major categories: neurotoxic, or nerve affecting, and hemotoxic, or blood affecting.
Actually all venom's have elements of both types, but one is more dominant than the other is. The neurotoxic type is more effective, usually acting on the central nervous system. That produces respiratory failure of the heart. Hemotoxins destroy blood cells, the lining of the blood vessels, and other tissue. Because of this the hemotoxic venom spreads more slowly and has a slower action than the neurotoxin's. Snakes have well-developed nervous system and they are very smart.
They are smarter than some fish and mammals and very adaptable to all conditions. When put in a hostile environment the harmless snakes can seem more dangerous than the venomous snakes. Snakes vision is well developed. They have an acute sense of smell and rely on it heavily when they are hunting. The tongue flicks out, picking up odors that carry to the roof of the mouth into contact with a sensory receptor called the Jacobson's organ.
The tongue also receives touch stimuli. Snakes are deaf to airborne sounds. They can perceive vibrations through the ground or whatever they are resting on. The pit vipers as well as some boas and pythons, have another type of sense organ. They have a heat receptor that can perceive small differences in temperature.
The receptors are located in the facial pit, between the eyes and the nostril. In boas the receptors are located in the labial pits. By this the snakes can find and catch warm-blooded prey at night. All snakes are carnivorous.
They eat a variety of animals from insects to spiders and frogs to rats. Snakes reproduce either by laying eggs or giving birth to live young. When the mother lays the egg or gives birth to the baby snake she abandons them. The birth of young and egg could as many as 100 at a time. The longest a snake has lived is 30 years in captivity.
Snakes are found in the warmer parts of the world. More than 2500 species are known and they are classified into 10 to 14 families. The Colubrid ae is the largest family. The latter groups are the most dangerous snakes in the worlds, such as mambas, cobras, and coral vipers. The largest type of snakes is in the Boi dae family, which include boas. Some can be as small as 2 feet while others can be giants and be as big as 26 to 33 feet.
A common name for a number of reptiles in a family of the crocodilian order is the Crocodile. The term crocodilian means members of the order, which include alligators, caimans, and gavials as well as obviously crocodiles. Some members of the crocodile family are the largest living reptiles. The Indo-Pacific, or saltwater, crocodile is the largest living reptile. It is known to grow a length of about 23 feet and weigh about 2000 pounds. This species inhabits the coastal waters of India.
A smaller species, the swamp crocodile, or mugger, is found inland waters of India. In America there are 4 species of crocodiles. The Cuban Crocodile which is restricted to Cuba; the Morelet's crocodile, which is about the same size as the Cuban Crocodile which is found on the Gulf Coastal Plain and Northern Guatemala. The Orinoco Crocodile which is found in the Orinoco River, And the American Crocodile, the largest crocodile in the Americas, which reaches to a length of 23 feet. This animal is found in southern Florida Including the Caribbean islands southern Mexico, Central America, and northern South America. Crocodilians first appeared about 200 million years ago and are believed to be remnants of the great age of reptiles.
Their ancestors originally lived on land and were lightly built, but they soon became water-dwelling, or aquatic, and amphibious forms. Except for the alligators, crocodilians live in tropical and subtropical areas of the world. Modern crocodilians are amphibious, spending much of their time in water... The tail is sometimes used to capture prey, sweeping it from shallow to deeper water, where it can be devoured more easily. Crocodilians are well-adapted as predators, with few natural enemies. Bony plates, called osteoderms, form a kind of armor in their thick skin.
Their teeth, about 30 to 40 in each jaw, are set into sockets in the jawbones and interlock when the mouth is closed. In crocodiles, the fourth tooth on each side of the lower jaw protrudes when the mouth is closed; in alligators, these teeth are not visible. The jaws of crocodilians are powerful enough in closing to crush the bones of small animals, but so weak in opening that they can be held together by hand. As the crocodilian floats almost completely underwater, its protruding nostrils and eyes and a portion of its back are the only parts visible as it stalks its prey. Crocodilians are the most vocal reptiles, producing sounds from quiet hisses to fearsome roars and bellows, usually during the mating season. On land, crocodilians move quickly in a belly crawl but can also gallop and walk mammal-like on all four legs.
Crocodiles are physiologically the most advanced reptiles; their internal anatomy resembles that of birds. They have a four-chambered heart and well-developed senses. Cold-blooded like all reptiles their body temperature depends on the environment crocodilians bury themselves in mud to or hibernate. In warm regions they are dormant during droughts; in colder regions, during winter. Crocodilians are egg-laying, reptiles, reaching reproductive maturity at about the age of ten. The eggs, 20 to 90 in number and about the size of goose eggs, are buried in sand, mud, or vegetable debris, where they are left to hatch by the heat of the sun or of vegetable decomposition.
Females of some species remain in the area to protect the nest and care for the newly hatched young, although many of the eggs and young are lost to predators. The parental behavior of crocodilians is unique among reptiles and points to their affinity with birds. Another reptile which has a hard shell that encloses the internal organs is a turtle or a tortoise. They have been around since the Triassic period, about 200 million years ago. There are about 250 species that are put into 12 families. Most families live in a freshwater habitat, and two families live in the sea.
Turtles vary widely in size. The North American Box turtle is about 6 inches or smaller, but the sea-dwelling leatherback can be up to 8 feet or more. The upper shell is called the carapace. The lower part of the shell is called the plastron. The two-part shell is connected to the vertebrate and the ribs.
The structure and size of the carapace and the plastron vary among different turtles. The shell is made of two parts or layers: an inner bony layer and the overlapping horny layer. The horny outer layer of some turtles has been used in making ornamental objects. Turtles have no teeth. They also lack a breastbone. The heart of a turtle has 3 chambers but it acts as though it has 4 due to the presence of an incomplete partition in the ventricle.
Most turtles are omnivorous, but some tortoises eat only vegetation, and some aquatic species are only carnivorous. All turtles lay eggs, which they bury, is soft sand or dirt. They generally live a long time. Some species live for more than 100 years. Tortoises are restricted to a single terrestrial family. The carapaces of tortoises are high and dome shaped.
The upper and lower shields of the tortoise are equipped with a hinge, which permits complete closure. Their thick shells and heavily scaled limbs afford effective protection against predators. As human habitation spreads the habitation of the turtle, crocodile and snakes disappear. Turtles out of all these reptiles are easiest to obtain because they are so slow moving and easily gotten for food. Whalers and pirates slaughtered many tortoises of the Galapagos Islands in order to supply fresh meat for the ship. In North America River channeling, swamp draining and high construction have taken away all these reptiles habitats making it very hard to survive..