Slither into the world of reptiles !

A reptile is an animal you are most likely to see in the warmer parts of the world. There are about 6,000 different kinds of reptiles and scientists have divided them into different groups which include around 20 crocodiles and alligators, 600 tortoises, terrapins and turtles, 2,500 lizards and a smaller number of snakes. Would you believe that one group contains only just one animal - a living fossil called the tuatara?

You may be aware by now that reptiles too just like any other animal group comes in different shapes and sizes. Some reptiles can be smaller than your finger while others can be many times larger than you. However, like with most other animals there are some things that are common between you and reptiles. That is like humans reptiles too have a skeleton and also breathe air .

When it comes to reptiles, you may have heard them being described as 'cold-blooded' creatures by many. Now what does that mean? It means that this particular group of animal does not have a 'thermostat' inside the brain like we do to keep the body at the same temperature all the time. Cold-blooded animals always have to rely on the sun to heat them up. They learn to adapt to the temperature in their environments. Although they are cold-blooded their body temperatures can soar to a level that would kill any mammal. So, unlike most other animals, reptiles can be active in very hot temperatures and live in the hottest places on the Earth. When the heat is uncomfortable even for them, they can hide underground during daytime and come out to hunt at night, when it is much cooler. One of the reasons they can stand the heat is their scaly skin which is generally hard-like in crocodiles and alligators. Snakes have thin scales.

As we explained reptiles are cold-blooded creatures and they are generally found in hot places, but several kinds of reptiles are found north of the Arctic Circle too, where the weather is cold for most part of the year.

Reptiles make their homes in all sorts of places - in deserts and forests, on plains and in water. Sea snakes and sea turtles live in the oceans. Crocodiles too live near water but usually the fresh water bodies such as lakes and rivers.

Many lizards and some snakes are good climbers and hunt for prey on the branches of trees. So they live on trees most of the time. Some reptiles live underground in burrows but a few make their homes in human houses and prey on insect pests.

Some humans don't mind them invading their homes because they eat the insect pests.

Where do the biggest reptiles live?

The biggest reptiles of all - the crocodiles and the longest snakes always live near water. Strangely the biggest land reptiles all live on tiny islands. These include the Komodo dragon (the biggest lizard) which lives on the island of Komodo and the giant tortoises of Galapagos Island. Scientists think that reptiles first got to small islands like the Komodo island by accident. Perhaps, the reptiles floated on trees that were washed into the sea by a big storm, and with no enemies around to attack them, grew to be the size they are today. Do you know that when some people first saw the Komodo dragon, they thought it to be a real dragon?

How do reptiles help us study evolution?

Scientists compare reptiles found in remote islands with their relations on the nearest mainland. They can often discover which sort of reptiles reached the island first, because it has had the most time to develop and so is least like its mainland cousins.

How often do reptiles eat?

Very large snakes like pythons and Anacondas don't need to eat often because once they gorge on huge prey, they don't hunt for food for days. It is the same with crocodiles and alligators. Some large crocodiles and snakes are known to have gone for over two years without meals. A crocodile could eat even a buffalo or a young giraffe.

Record holders

The world's largest and heaviest reptile - Saltwater Crocodile which has its origin in Australia.It can grow to lengths of stet metres.The Saltwater Crocodile is also one of heaviest reptiles.Some of the largest reptiles alive today include the leatherback turtle, the Komodo dragon, and the saltwater crocodile. The leatherback turtle is the largest turtle species. Adult leatherbacks grow to an average length of stet metres and can weigh between 250 and 700kg. The Komodo dragon is the largest lizard species and can grow in excess of 3 metres in length and 70kg in weight. The saltwater crocodile is the largest of all living reptiles and can weigh between 600 and 1,000kgm. Saltwater crocodiles grow to lengths of between 4 and 5.5 metres.The heaviest reptile is the marine leatherback turtle, at 0.8 tons

(1600 pounds)

The world's longest reptile - The reticulated python is the longest recorded snake and reptile overall, with some reports of it exceeding 30ft!

The world's smallest reptile - Four new species of miniaturised chameleons rank among the smallest known reptiles in the world. The super-tiny lizards, identified in Madagascar, measure just tens of millimetres from head to tail. In some cases, they are even small enough to stand on the head of a match, ranking among the smallest reptiles in theworld.The chameleons, described in the journal PLoS ONE, either tie or beat out the prior smallest lizard record-holder, the dwarf gecko whose snout-vent length is at most 18 mm, with a total length of 33 mm (1.3 inches).The British Virgin Islands gecko was also listed as the smallest reptile standing at about 3/4 inches in length.

Reptiles are divided into four groups.

Turtles are among the most ancient of the reptiles alive today and have changed little since they first appeared some 200 million years ago. They have a protective shell that encloses their body and provides protection and camouflage. Turtles inhabit terrestrial, freshwater, and marine habitats and are found both in tropical and temperate regions.

Squamata are the most diverse of all the reptile groups and include lizards, snakes and worm-lizards. There are nearly 7,600 species of squamates alive today. The earliest squamate fossils date back to the beginning of the Jurassic Period. Squamates shed their skin periodically and have jointed skulls and jaws that enable them to capture larger prey and bite with great power.

Crocodilians first appeared during the late Cretaceous Period, about 84 million years ago. The group includes alligators, crocodiles, gharials, and caimans. Crocodiles are the closest living relatives to birds.

Tuataras are a group of reptiles that are lizard-like in appearance but they differ from members of the Order Squamata in that their skull is not jointed. Tuataras were once widespread but today only two species of remain. Their range is now restricted to just a few islands in New Zealand.

[Fast facts]

* There are about 8,000 species of known reptiles alive today.

* The first reptiles appeared approximately 340 million years ago during the Carboniferous Period from a group of reptile-like amphibians called the reptiliomorphs. Early reptiles included organisms such as Hylonomus, Petrolacosaurus, Archaeothyris, and Paleothyris. The oldest evidence of reptiles is a set of footprints found in Nova Scotia.

* Reptiles are tetrapods.They have four limbs, a characteristic that places them among the group of animals known as tetrapods. It should be noted that although some reptiles such as snakes and amphisbaenians have lost their legs during the course of evolution, they are tetrapods by descent.