Reptiles


Reptiles were the first true land-dwelling vertebrates. The appeared over 300 million years ago. Common reptiles include snakes, lizards, turtles, crocodiles and alligators.

The most noticeable feature of reptiles are the scales that cover their body.
Although reptiles breathe through lungs, some reptiles can also absorb oxygen in water through membranes in their mouth.

Reptiles are often called cold-blooded because they can't regulate their own body temperature. Their body temperature depends on the external temperature.

They are characterized by breathing air, laying shelled eggs, and having skin covered in scales and/or scutes. Reptiles are classically viewed as having a "cold-blooded" metabolism. They are tetrapods (either having four limbs or being descended from four-limbed ancestors).

Modern reptiles inhabit every continent with the exception of Antarctica, and four living orders are currently recognized:
  • Crocodilia (crocodiles, gavials, caimans, and alligators): 23 species
  • Sphenodontia (tuataras from New Zealand): 2 species
  • Squamata (lizards, snakes, and worm lizards): approximately 7,900 species
  • Testudines (turtles and tortoises): approximately 300 species




    Facts on Reptiles



    Biggest (Most Massive) reptile - the estuarine crocodile (over 7 m (23 ft) long).

    Smallest reptile (and smallest lizard) - the British Virgin Islands gecko (only 18 mm = 7/10 inches long)


    Fastest reptile - the spiny-tailed iguana (tracked at 34.9 km/h = 21 mph)

    Biggest (heaviest) snake - the anaconda of South America.

    Longest Snake - reticulated Python (over 10 m long)

    Fastest-moving snake - probably the poisonous black mamba

    Biggest lizard - the Komodo dragon (up to 3 m long)

    Biggest turtle - the leatherback turtle (up to 2.5 m)


    Most poisonous land snakes - the taipan (from Australia), black mamba, and krait.


    Only poisonous lizards - the Gila monster, the beaded lizard

    Weirdest ability - horned lizards can squirt a thin spray of blood from their eyes up to of 3 feet (0.9 meter) away.


    Crocodiles and alligators are large amphibious reptiles. They can walk on land using their webbed feet. They can also use their long tail to swim in water. Crocodiles feed on large animals they catch on land or in water. They have powerful jaws and teeth to tear apart their prey.


    The turtle and tortoise are different from other vertebrates in that they have a shell. The shell is made of skin tissue and bony plates.

    Giant tortoises can grow up to 4 feet long and live about 100 years.



    Snakes


    Snakes are covered with scales, many times of various colors. As humans shed some of their skin, the snakes also shed their outer skin many times during the year. This is called molting. The snakes finds a stone or twig to rub up against and then pushes and pulls against it until the skin comes off.

    The snake is one reptile that has no legs. It makes up for this by its scales on the underside of its body called scutes. It also has very strong muscles that help it move. They can move in curves from side to side or up and down. Snakes move quite slowly compared to other animals. The fastest they can move is several miles per hour.

    The snake has no eyelids, but has a transparent covering to the eye to protect it. Some have round eye pupils and some have oval pupils. The snake has a long forked tongue that it uses to smell things with.

    The snake has a very big mouth with two rows of teeth on each side of its upper jaw and one row on its lower jaw. The teeth, however, are not used for chewing, but to hold onto its prey. The snake eats its prey whole. The teeth slant backward to push the prey back into the snake. Its jaws stretch very far open so that the snake can take in animals bigger than itself.

    Snakes solely eat animals. Many snakes such as the garter snake open their mouths and swallow their prey whole. Others such as the boa and python, wrap their bodies around their prey and squeeze it to death. They snakes are usually larger and more powerful. Snakes such as the rattlesnake, water moccasin, cobra, copperhead and coral snake, have huge fangs that poison in them. These snakes attack their prey and the hollow fangs fill with poison from poison glands around the fangs. The prey dies and the snake eats it.

    A few snakes such as the garter snake have live birth. Most snakes lay eggs that contain food for the young snake.


    Lizards


    There is a huge size range for lizards from tiny skinks to Komodo dragons that are up to 5 meters long. Lizards generally live in the tropical zone where it is very warm.

    Lizards differ from snakes in that they have four feet and can move quite quickly.

    One well known snake is the chameleon. Its tale is one and one half the size of its body, which is around two inches. It changes its color constantly.

    The Gila monster is a poisonous lizard and lives in the American Southwest. It is several feet long and has brown or black skin with colored splotches. It has poisonous glands in its jaw which can kill a man when the Gila monster gives a hard bite.

    The horned toad is really a lizard, despite its name. It is found in the western United States. It has scales of different lengths and some of them have live birth of their babies versus laying eggs as most reptiles do.

    The iguana is a lizard of the tropics. It resembles a tiny dragon.



    Turtles


    Turtles live on land, in fresh and salt water. If they live on land, they are called tortoise and some fresh water turtles are called terrapins.

    Turtles can range in size from a few inches to three meters. All turtles have two shells with their bodies sandwiched in between. Its head can be pointed or shaped like a triangle. It has a jaw that forms a beak, but has no teeth. It has good eyesight with upper and lower eyelids. It has a third eyelid called a nictitating membrane that covers the eye.

    The turtle walks quite slowly due to its body shape and its short legs. It has five toes on each leg and claws on the toes. Turtles' toes are webbed to a greater or lesser degree.

    Some turtles have tails, while others don't. Turtles all lay their eggs on land in shallow holes covered with sand. Turtles eat insects, worms, plants, fish and frogs.



    Alligators and Crocodiles


    Alligators and crocodiles are in the same reptile subgroup. They mostly live in tropical or semitropical regions. Alligators are mostly found in the southern United States and the crocodiles in Africa, India, South America, and southern United States. They are among the largest reptiles. Their bodies are covered with scales and they have webbed toes. They live in swamps and along the banks of rivers.

    The crocodile spends more time in the water than the alligator. The crocodile has a narrower, more triangular head and a pointer snout. The crocodile is grayish-green in its color. The crocodile is more active than the alligator.

    The alligator is brownish in color and moves more slowly than the crocodile.

    Both the alligator and crocodile eat fish and nearby land animals. They can also attack man.



    Amphibians



    Amphibians are members of the class Amphibia, subphylum Vertebrata, phylum Chordata. The class Amphibia includes frogs, toads, salamanders, newts and caecilians. Amphibians are characterized by a glandular skin without external scales, by gills during development (and in adulthood in some), and by eggs that may have jelly coats but develop without formation of extraembryonic membranes such as the amnion. Most amphibians also have four limbs. Limbs and lungs are adaptations for life on land; the limbs evolved from the ancestral fishes' lobed fins. The scales and amniote egg evolved by reptiles are further adaptations for life on land and distinguish reptiles from amphibians.

    in total they number approximately 6,500 species. Many amphibians lay their eggs in water. Amphibians are superficially similar to reptiles, but reptiles are amniotes, along with mammals and birds. The study of amphibians is called batrachology.


    Amphibians are ecological indicators, and in recent decades there has been a dramatic decline in amphibian populations around the globe. Many species are now threatened or extinct.


    Amphibians evolved from animals that lived in the sea several hundred million years ago. The earliest fossils of amphibians date back over 350 million years. The most common amphibians are the frog, toad, salamander and newt


    Depending on the species of amphibian, breathing can take place in gills, lungs, the lining of the mouth, the skin, or some combination of these.
    Amphibians body temperature changes with its environment. In cold climates, amphibians hibernate during the winter.

    The class Amphibia comprises three living orders and several extinct ones. The living members of the class include those forms which have been mentioned above. Amphibians are thought to have arisen from lobe-finned crossopterygian fishes. Considerable conjecture exists, however, as to whether amphibians actually arose from several lineages. Some Swedish experts tend to favor separate lineages for each of the modern orders; certain British and U.S. scientists support the idea of two lineages, one giving rise to frogs, the other to salamanders and caecilians. The characteristics of vertebrae, teeth, and skull bones form the basis for these hypotheses. Additional developmental and variational data are necessary to support these ideas.

    Two major subclasses of extinct amphibians are found in the fossil record. They are the Labyrinthodontia and the Lepospondyli. The amphibians of the Labyrinthodontia, which lived during the late Devonian through Triassic periods (345 to 190 million years ago), include the most primitive amphibians represented by the genus Ichthyostega. They were fresh-water carnivorous animals, with tail fins, small scales, and a fishlike vertebral column. Their skulls had many bones, as did those of their presumed crossopterygian ancestor. The Labyrinthodontia, according to the U.S. paleontologist Alfred S. Romer, include three extinct orders: the Ichthyostegalia, the Temnospondyli, and the Anthracosauria. The Anthracosauria are thought to be the ancestors of reptiles and hence of modern birds and mammals. The Temnospondyli are thought by some scientists to be the ancestors of the modern frogs.

    The amphibians of the subclass Lepospondyli, which lived during the Mississippian through lower Permian periods (340 to 270 million years ago), include the extinct orders Nectridea, Aistopoda, and Microsauria. Members of the latter two orders were elongate. Some had limbs, some had reduced limbs, and some had no limbs. Many scientists suggest that the ancestors of modern salamanders and caecilians are among the lepospondyls.

    The modern, extant orders of the Amphibia are placed in the subclass Lissamphibia. The superorder Salientia includes extinct froglike forms, and the extant order Anura consists of the frogs and toads. The superorder Uordela and order Caudata include the salamanders. The superorder Gymnophiona includes a newly discovered fossil with small limbs and the living limbless caecilians, order Apoda. These three groups are allied in the Lissamphibia by characteristics of tooth, skin, and fat body structure. Vertebral and skull structure, as well as other characteristics, differ markedly among the three groups. This suggests to many scientists separate origins for each of the three modern orders.



    Facts about frogs


    * A frog is an amphibian.

    * More than 4,000 types of amphibians exist in this world, out of which only 45 species are found in Europe.

    * A frog is cold blooded (poikilothermic).

    * Frogs range from 1cm to 30cm in length.

    * Frogs are unable to live in the sea or any salt water.

    * Frogs are able to lay 4,000 eggs at one time.

    * Frogs have webbed feet and long back legs which they use for jumping and swimming.

    * Frogs do not need to drink water, as they are able to absorb water through their skin.

    * A frog is able to change the color of its skin to match its surroundings.

    * The eyes and nose of a frog are located on top of its head. This feature enables it to breathe and see, when most of its body is submerged in water.

    * While under water, the frog’s eyes are protected by a transparent eye lid called a nictitating membrane.

    * Frogs use their long sticky tongue to capture their food.

    * Most frogs eat small insects like flies and cockroaches. The larger ones eat snakes, small mammals, birds and even other frogs.

    * The factors that determine a frog’s habitat are rainfall, soil type, places of refuge and calling and egg laying sites.

    * Each species of frog is blessed with a unique call, which is used to mark out a territory and attract females of the same species.

    * Frog eggs, or spawn undergo a change in body structure and physiology, from the tadpole stage to the adult frog stage.

    * Some frogs are able to jump up to 20 times their own body length in a single leap.

    * The Scottish highlands house the biggest frog.

    * A toad is dry and has warts. It prefers to walk instead of jump.

    * Goliath frog (Conraua goliath) from West Africa is the largest known frog with a body length that exceeds 30 cms.

    * The smallest frog that is known, is a Brazilian species (Psyllophryne didactyla) that has a maximum length of less than 1 cm.


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