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Unique Features of Reptiles

Reptiles first appeared on the earth about 315 million years ago, having apparently arisen from an amphibian ancestor. They share unique anatomical traits, including special modifications of their skin and eyes, the skull and backbone, and an external nasal gland. Over 6500 species are distributed world-wide on all continents except Antarctica. Due, in part, to their minimal food requirements, reptiles occupy nearly every habitat imaginable, including the world's oceans, desert and montane (mountainous) regions as high as 16,500 feet above the sea-level. Most reptiles are ectotherms, maintaining appropriate body temperatures by basking in optimal conditions, although some hormonal and muscular systems are involved in heat production in some species. During inclement seasons reptiles can suspend many functions and remain dormant.

There is considerable size variations among reptiles: tiny geckos and chameleons measure less than one inch in length; Komodo monitors reach 10 feet.; Anacondas and areticulated Pythons may be 25 feet and more; Leatherback turtles and Indopacific Crocodiles have weights approaching a ton.

Reptiles and Humans

This diverse group of animals has influenced humans throughout recorded history. Objects of both revulsion and veneration since ancient times, reptiles figure strongly in myth and folklore. They have gained great popularity recently as the burgeoning field of herpetology reveals their interesting lifestyles. Ranging from the bizarre to starkly beautiful, reptiles present a panorama of shapes and colors.

Vulnerable Groups of Reptiles

Modern reptiles encompasse two venerable lineages: one includes the turtles and tortoises, while the other includes lizards, snakes, worm lizards, tuataras, and crocodilians. Recent evidence indicates that the Reptiles cannot be separated reliably from the birds, with whom they haoeve any shared traits.

Physical Characteristics

Typical reptiles possess dry skin covered with scales. Snakes also have a brille, or protective eye covering. Like other animals, reptiles shed their skin, but they do so at one time rather than continually. They may be limbless or nearly so, and some lizards and some worm lizards, possess only one pair of limbs. Limbless terrestrial reptiles move via some form of undulation. Those with limbs crawl, while some lizard species rear up, using only the hind limbs, when running fast.

Fertilization

Fertilization is internal, and in most reptile species there are sex differences in size and color. Certain lizard populations consist entirely of females, each genetic duplicates of the other. One island population of snakes is entirely hermaphroditic, with all individuals possessing both male and female characteristics. The majority of reptiles produce leathery-shelled eggs which, in contrast to amphibians, are resistant to drying.

Nests

Crocodilians and most turtles construct nests of vegetation or excavate burrows for their eggs. All other reptiles deposit their eggs in humus, or the forest floor, or adhered to bark or something similar. Many kinds of snakes and lizards display the same type of viviparity, producing live young. Parental care is largely absent in reptiles, with offspring quite capable of subsisting on their own from birth. However, some lizards and snakes brood their eggs, and egg-brooding and parental care in crocodilians is widely documented. In some species of turtles and crocodilians, the sex of the offspring is determined by the temperature during incubation.

Natural Predators

Reptiles are preyed upon by a variety of organisms including humans, other reptiles, amphibians, birds, mammals, fishes, and many kinds of invertebrates. Some of their defense mechanisms involve camouflage (direct resemblance to something in the environment), cryptic or disruptive coloration (rendering the animal difficult to see), mimicry (resembling something noxious), a wide variety of their displays (including puffing, flattening, gaping, and hissing), death feigning, fleeing the scene (even via gliding), biting, scratching, and lashing or breaking the tail.

Threat to Humans

Although most of negative image of reptiles is unfounded, some species are capable of causing suffering or death in humans. Several species of crocodilians have preyed on humans, sometimes in considerable numbers, especially in Africa and Indonesia. There are many dangerously venomous species of snakes throughout the world, and even the venomous Gila Monster (Heloderma) and the large Komodo Monitor (Varanus) have caused human fatalities. Thus, it is not surprising that reptiles have been the object of considerable toxicological and behavioral research.

Petting an alligator

Pet alligators and snakes do not respond to cuddling and petting because they don't feel emotions beyond anger, fear, and pleasure.

Mammals, in contrast, nurture and care for their young. They have a sense of family and community. They play and bond with one another. Many mammals live and hunt in packs, and they guard and protect members of the pack. For this, you need more than a reptilian brain had to offer. What eventually developed was a small collection of gray matter, called the limbic system, located immediately above and incircling the brainstem.

The limbic system developed with two things in mind. First, emotions had to be connected to memory, because emotionally charged events needed to be remembered. You don't want a child touching a hot stove more than once. Attaching an emotional handle to events not only makes it easier to remember, but it also makes us want to remember it.

The second task for the developing limbic system was to express emotions with changes in heart rate, breathing, blushing sweating, bowel control and all the other features of the fight or flight response. To do this, the limbic system was attached to the hypothalamus, the part of the brain that sends out signals to express our emotions physically through the sympathetic and parasympathetic nervous system.


Comments

By Guest_3444   Thursday, April 10, 2008

Since 1971, the signing of international convention by the governments of many nations has somewhat eased the situation of endangered turtle species. Convention for the safeguarding and wise use of wetlands was adopted. Although it was aimed at the conservation of the habitats of aquatic birds, it was also designed to protect the animals in the world's major wetlands. On April 30, 1973, CITES, the Convention of international Trade in Endangered Species of Wild Fauna and Flora, was signed in Washington. This treaty provides for scientific control and scrupulous administration in every individual case involving the import or export of protected plants and animals, carrying heavy fines and penalties for any eventual breaches and irregularities. The species under consideration, which nevertheless constitute only a minimal part of those that make up international traffic, are catalogued in appendices according to their level of protection and therefore of commercial restriction. Appendix I lists the species most at risk, for which commerce is as a rule is completely prohibited, while Appendices II and III list respectively endangered species for which international commerce is restricted or controlled, or those for which one nation alone has requested trade restrictions. The lists are periodically brought up to date, and if need be, the levels of protecton are modified and set out in various appendices. but the lak of data concerning the situation in the wild of a large number of species prevents their timely consideration and inclusion; consequently, it is all too likely that some species will be wiped out by excessive depredation and commerce even before they are catalogued.

By Guest_3444   Thursday, April 10, 2008

Since 1971, the signing of international convention by the governments of many nations has somewhat eased the situation of endangered turtle species. Convention for the safeguarding and wise use of wetlands was adopted. Although it was aimed at the conservation of the habitats of aquatic birds, it was also designed to protect the animals in the world's major wetlands. On April 30, 1973, CITES, the Convention of international Trade in Endangered Species of Wild Fauna and Flora, was signed in Washington. This treaty provides for scientific control and scrupulous administration in every individual case involving the import or export of protected plants and animals, carrying heavy fines and penalties for any eventual breaches and irregularities. The species under consideration, which nevertheless constitute only a minimal part of those that make up international traffic, are catalogued in appendices according to their level of protection and therefore of commercial restriction. Appendix I lists the species most at risk, for which commerce is as a rule is completely prohibited, while Appendices II and III list respectively endangered species for which international commerce is restricted or controlled, or those for which one nation alone has requested trade restrictions. The lists are periodically brought up to date, and if need be, the levels of protecton are modified and set out in various appendices. but the lak of data concerning the situation in the wild of a large number of species prevents their timely consideration and inclusion; consequently, it is all too likely that some species will be wiped out by excessive depredation and commerce even before they are catalogued.


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