Reptiles
Edition number one
Contents
Origin of reptiles
3
Evolution of reptiles
4
Where do reptiles live?
5
Facts about reptiles
6
Life of reptiles
7
The four main groups of reptiles
8
Snakes
9
Crocodiles
10
Lizards
11
Chameleons
12
2
These animals originated around 320 million to 310 million years ago with the first reptiles evolving from the advanced reptiliomorph labyrinthodonts. Animals from the Casineria genus are the earliest animals suspected to be amniotes rather than advanced amphibians. The origin of reptiles occurred in steaming swamplands of late Carboniferous period. Fossils found in Nova Scotia show footprints with imprints of scales and typical reptilian toes. The prints have been attributed to Hylonomus which is the earliest recognized reptile. Hylonomus was a lizard-like creature (8 to 12 in long) with sharp teeth that indicates an insectivorous diet.
3
Evolution of reptiles
The following anatomical changes transformed the ancestral amphibians into land adapted reptiles: V
Skull became monocondylic for better movement and flexibility. Atlas and axis
vertebrae together permitted skull movement in all directions. V
Limb bones and girdles became stronger but limbs were attached on the sides of
body, and belly touched the ground during creeping mode of locomotion. V
Sacral region involved two strong and fused vertebrae to support the body weight
on hind legs. V
Body developed a covering of epidermal scales to prevent loss of body moisture,
and skin glands were lost.
4
Where do reptiles live?
Reptiles prefer to live in warm, dry climates rather than wet ones. They are most numerous in areas such as deserts and semi-deserts. However, reptiles can be found on every continent except for Antarctica. Reptiles have adapted to live in a variety of environments, including water, deserts, jungles, forests, and mountains. The reptiles that live in water can do so temporarily or permanently, depending on the species. Reptiles are not like fish, however, and cannot breathe in water. While reptiles can live almost everywhere, some specific species can only live in certain areas. For instance, the Gila Monster, which is one of the two venomous lizards, lives in the arid and semiarid regions of the United States and Mexico, but its habitat is being threatened due to urban development. Different reptiles tend to live in different areas. Turtles and some snakes, for instance, live in water, while some reptiles like the Mexican Bearded Lizard can thrive in the deserts of Mexico. Crocodiles are found primarily in subtropical regions. Snakes are the most prevalent, with snakes living in almost every type of habitat around the world.
5
Facts about reptiles Nearly all reptiles lay shelled eggs. Reptiles breathe air. Reptiles are covered in scales or have a bony external plate such as a shell. Nearly all reptiles are cold blooded. The first reptiles are believed to have evolved around 320 million years ago. The size of reptile’s brains relative to their body is much smaller than that of mammals. Reptiles use a variety of methods to defend themselves from dangerous situations, such as avoidance, camouflage, hissing and biting. Crocodiles and alligators are reptiles. Turtles and tortoises are reptiles. Lizards and snakes are reptiles. Lizard and snake species make up the largest number of different reptiles. Tuataras found in New Zealand are reptiles.
6
Life of reptiles
Great diversity marks the reptile family, which includes snakes, lizards, alligators and turtles. But all reptiles share several similarities. All reptiles are coldblooded, which means they are ectotherms -- they rely on the environment to generate body heat. They have similar life cycles that begin as eggs and progress to hatchlings and then to juveniles before they arrive at the adult stage of life.
Egg Reptiles begin their lives as embryos in amniotic eggs. This means the embryos are cushioned and protected by a surrounding amniotic membrane. These eggs are larger than eggs that do not have amniotic membranes. The egg yolk is another part of the egg; it provides nourishment for the embryo. A separate membrane eliminates waste and provides gas exchange. In most cases, the eggs are buried or placed underground after fertilization. Some reptiles, such as garter snakes, give birth to live young. Some hold the eggs inside until they hatch. A very small group of reptiles compose an exception: The armadillo lizard is one species nourished in a placenta instead of in an egg.
Hatchling When a reptile is ready to hatch, the creature uses an egg tooth to break through the shell of the egg. Once the shell is opened, the baby will typically remain in the shell for 12 to 48 hours. The little reptile is able to care for and defend himself from birth.
Juvenile Juvenile reptiles look similar to the adults of their species -- they do not undergo the metamorphosis common in insects and amphibians. Reptiles grow slowly until they reach adult size and sexual maturity. The time a reptile spends as a juvenile varies by species. The green iguana, for example, reaches adulthood and sexual maturity when it is approximately 16 months old and 9 inches long from snout to vent.
Reproduction Mature reptiles reproduce sexually. Once a male has mated with a female, the female can store the sperm for up to six years to fertilize future hatches of eggs. Once a batch of eggs is fertilized, the female reptile will bury the eggs in a hole or lay them underground. In most cases, the female reptile leaves the eggs to hatch alone. Some reptiles, such as pythons and crocodilians, will care for and protect the eggs until they hatch. Some reptiles who give birth to live young will also provide some care for the hatchlings.
Adulthood and Life Span The time a reptile spends in adulthood varies greatly. Some reptiles have fairly short life spans. For example, corn snakes may only live 6 to 8 years in the wild. Other reptiles live much longer. Alligators have life spans of 35 to 50 years; desert tortoises can live 80 years or more.
7
The four main groups of reptiles
Crocodilians Crocodilians are a group of large reptiles that includes alligators, crocodiles, gharials, and caimans. Crocodilians are formidable predators with powerful jaws, a muscular tail, large protective scales, streamlined body, and eyes and nostrils that are positioned on top of their head.
Squamates Squamates are the most diverse of all the reptile groups, with approximately 7,400 living species. Squamates include lizards, snakes and worm-lizards.
Tuatara Tuatara are a group of reptiles that are lizard-like in appearance but they differ from the squamates in that their skull is not jointed. Tuatara were once widespread but today only two species of remain.
Turtles Turtles are among the most ancient of the reptiles alive today and have changed little since they first appeared some 200 million years ago.
8
snakes Anatomy Snakes constitute the suborder Serpentes (or Ophidia). In most snakes limbs are entirely lacking, but a few have traces of hind limbs. The skin, which is covered with horny scales, is shed, usually several times a year. The extremely long, narrow body is associated with distinctive internal features. The number of vertebrae is much larger than in most vertebrates, paired internal organs are arranged linearly rather than side by side, and only one lung is developed, except in members of the boa family, which have two lungs. The jaws of snakes are loosely jointed and extremely flexible. The pointed, backward-curved teeth are fused to the supporting bones of the head. There are no ears or movable eyelids; the eyes are covered by transparent "spectacles," or ocular scales. Snakes have good vision. They do not hear airborne sound waves, but can perceive low-frequency vibrations (100–700 Hz) transmitted from the ground to the bones of the skull. A chemosensory organ opens into the roof of the mouth; it receives stimuli from the forked tongue that constantly tastes the surroundings as the animal moves along. Snakes have no larynx or vocal chords, but are capable of producing a hissing sound. Locomotion and Limblessness A snake moves by means of muscular contraction, which can produce several types of locomotion, the commonest types being undulation and straight-line movement. Straight-line movement is aided by the ventral plates, elongated scales on the abdomen that overlap with their open ends pointing toward the tail. These plates can be moved forward by means of muscles attached to the ribs. It is believed that snakes are descended from lizards, but how and why they evolved toward limblessness is uncertain. Some paleontologists have held that limblessness was an evolutionary advantage in the dense vegetation that formed the early environment of snakes, or that it developed to facilitate burrowing habits, but others believe that the earliest snakes evolved in an aquatic environment and are descended from marine reptiles related to mosasaurs. The fossil evidence for a land or marine origin is inconclusive. Predation Small snakes feed on insects and larger ones on proportionately larger animals. Their teeth are designed for catching and holding prey, but not for chewing. The construction of the jaws, the ribs, and the expandable skin enable them to swallow very large prey whole. Some snakes capture animals by pinning them to the ground; some—the constrictors—crush them by wrapping their bodies around them and squeezing; still others—the venomous snakes— inject poison into their victims. The poison, or venom, is produced by modified salivary glands from which it passes through either a groove or a hollow bore in the fangs, the enlarged, specialized teeth found in venomous snakes. A snake may bite a person when threatened or alarmed; if the snake is venomous the bite can sometimes prove fatal (see snakebite). Only by familiarity with the appearance of particular species, or by examination of the fangs, can the venomous snakes be distinguished from the harmless ones. Reproduction Fertilization is internal in snakes; as in lizards, the males have paired copulatory organs, either of which may be used in mating. Females of some species can store sperm for several years to insure future fertilization. In most species the female lays eggs; in some the eggs are incubated and hatched within the mother's body; in a few there is true viviparity, or live birth, with the young nourished by means of a placenta rather than an egg. Some egg-laying snakes brood the eggs, but there is no parental care of the young.
9
Crocodiles
A crocodile’s physical traits allow it to be a successful predator. Its external morphology is a sign of its aquatic and predatorylifestyle. Its streamlined body enables it to swim swiftly, it also tucks its feet to the side while swimming, which makes it faster by decreasing water resistance. They have webbed feet which, though not used to propel the animal through the water, allow them to make fast turns and sudden moves in the water or initiate swimming. Webbed feet are an advantage in shallower water, where the animal sometimes moves around by walking. Crocodiles have a palatal flap, a rigid tissue at the back of the mouth that blocks the entry of water. The palate has a special path from the nostril to the glottis that bypasses the mouth. The nostrils are closed during submergence. Like other archosaurs, crocodilians are diapsid, although their post-temporal fenestrae are reduced. The walls of the braincase are bony, but lack supratemporal and postfrontal bones.[20] Their tongues are not free, but held in place by a membrane that limits movement; as a result, crocodiles are unable to stick out their tongues.[21] Crocodiles have smooth skin on their bellies and sides, while their dorsal surfaces are armoured with large osteoderms. The armoured skin has scales and is thick and rugged, providing some protection. They are still able to absorb heat through this armour, as a network of small capillaries allows blood through the scales to absorb heat. Crocodilian scales have pores believed to be sensory in function, analogous to the lateral line in fishes. They are particularly seen on their upper and lower jaws. Another possibility is that they are secretory, as they produce an oily substance which appears to flush mud off.
10
Lizards Lizards typically have feet and external ears, while snakes lack both of these characteristics. However, because they are defined negatively as excluding snakes, lizards have no unique distinguishing characteristic as a group.[citation needed] Lizards and snakes share a movable quadrate bone, distinguishing them from the sphenodonts, which have more primitive and solid diapsid skulls. Many lizards can detach their tails to escape from predators, an act called autotomy. Vision, including color vision, is particularly well developed in most lizards, and most communicate with body language or bright colors on their bodies, as well as with pheromones. Lizards are the most speciose clade among extant non-avian reptiles, comprising about 60% of all living species. The adult length of species within the suborder ranges from a few centimeters for chameleons such as Brookesia micra and geckos such as Sphaerodactylus ariasae to nearly 3 m (9.8 ft) in the case of the largest living varanid lizard, the Komodo dragon. Some extinct varanids reached great size: The giant monitor Megalania is estimated to have reached up to 7 m (23 ft) long; while the extinct aquatic mosasaurs reached 17 m (56 ft).
11
chameleons Chameleons are unique lizards that live in a variety of climates and locations. Half of all the species are from Madagascar and the rest can be found in Africa, the Middle East, Europe, and Asia. Chameleons are arboreal and have adapted to live their lives in trees. They are carnivores that feed primarily on insects, but some will also eat small reptiles and other vertebrates. Chameleons have some amazing physical features. Most have eyes that move independently and have a very long projectile tongue. Some species can extend their tongue up to twice the length of the body. They have a prehensile tail that helps them climb and balance on branches. To aid a life in trees, their hands and feet have fused to be pincer-like which helps them grasp branches. These reptiles also have flattened bodies, another adaptation for an arboreal lifestyle. They are often colorful lizards and can be green, blue, brown, black, orange, yellow, as well as other colors. Some can change their color which can represent emotions like fear or anger, or it is used as a way to regulate heat. A few species color change to blend into their surroundings and hide from predators. Chameleons vary greatly in size, color, and longevity. The smallest species is less than two inches long and the largest can be up to thirty inches long. They live fairly short lives and depending on the species can live from a few years up to around ten years.
12
13
http://animals.mom.me/life-cycle-reptiles-eggs-adults-8518.html http://www.sciencekids.co.nz/sciencefacts/animals/reptile.html https://www.reference.com/pets-animals/reptiles-live-f6d1848935b0a763# http://animals.about.com/od/reptiles/tp/reptilegroups.htm
14