Shedding and regenerating tails
Lizards like geckos and skinks, when captured by the tail will shed part of the tail structure and escape.This process called autotomy. The detached tail will continue to wiggle and distract the predator's attention while the prey, i.e. the lizard flees. The detached tails of leopard geckos can wiggle for up to 20 minutes. In many species the tails have an intense colour in order to tempt the attacker to strike it first. In the shingleback skink and some species of geckos, the tail is short and broad and resembles the head, so that the predators may attack it rather than the more vulnerable front part.
It take a few weeks for the tail to grow back. The new section will however contain cartilage rather than bone, and will never grow to the same length at the original tail. It is often also distinctly discolored compared to the rest of the body and may lack some of the external sculpting features seen in the original tail.
Reptiles in Human Culture
Reptiles have played important roles in many human cultures, and human cultures have a heavy impact on reptile populations. Turtles have also served as food for millennia, as have other reptiles. Reptiles have also been used as medicine, especially in China. Human impact has threatened many reptile species with extinction. But at the same time, reptiles have been an integral part of some cultures. In Hindu mythology, one of the famous avatars of Lord Vishnu was that of the turtle Kurma. He also has a snake with seven heads guarding him. Lord Shiva happens to use a snake as a garland and in every temple of Lord Shiva, one would find an idol of a snake.
Earliest reptiles were largely overshadowed by bigger labyrinthodont amphibians, such as Cochleosaurus, and remained a small, inconspicuous part of the fauna until the Carboniferous Rainforest collapsed. This sudden collapse affected various groups. Amphibians were devastated, while reptiles survived and fared better, since their bodies adapted to the drier conditions that followed. Amphibians need to be in water to lay eggs. But reptiles could lay eggs since those possess a shell that allows them to be laid on land. They acquired new niches at a faster rate than before the collapse. They acquired new feeding strategies including herbivory and carnivory, previously only having been insectivores and piscivores. From this point forward, reptiles dominated communities and set the stage for the Mesozoic era (known as the Age of Reptiles). Mesosaurus, one of the earliest known reptiles was a genus from the early Permian who had returned to water, feeding on fish.
Modern reptiles exhibit some form of cold-bloodedness, so that they have limited the physiological means of keeping the body temperature constant are limited. They often rely on external sources of heat. Their core temperature is less stable than birds and mammals and hence they need enzymes capable of maintaining efficiency over a great range of temperatures. The optimum body temperature range varies with species, but is typically below that of warm-blooded animals. For many lizards, it is anywhere between 24°C to 35 °C (75°–95 °F), while extreme heat-adapted species, like the American desert iguana Dipsosaurus dorsalis, can have optimal physiological temperatures in the mammalian range, between 35° and 40 °C (95° and 104 °F). While the optimum temperature is often encountered when the animal is active, the low basal metabolism makes body temperature drop rapidly when the animal is inactive.
Muscle action produces heat in all animals and this is where reptiles are no exceptions. Large reptiles have a low surface to volume ratio which allows this metabolically produced heat to keep the animals warmer.
The benefit of a low resting metabolism is that it requires far less fuel to sustain bodily functions. By using temperature variations in their surroundings, or by remaining cold when they do not need to move, reptiles can save considerable amounts of energy compared to endothermic animals of the same size. A crocodile would need only one tenth or at maost one fifth of what a lion would need to eat to surivive and it can go for six months without food. Adaptive metabolisms and lower food requirements permit reptiles to dominate in regions where birds and warm blooded animals won't find enough food to sustain.
It is generally assumed that reptiles are unable to produce the sustained high energy output necessary for long distance chases or flying. Higher energetic capacity might have been responsible for the evolution of warm-bloodedness in birds and mammals.
Ever seen lizards crawling on the walls, or turtles in the sea and out of it? And in case you have seen crocodiles and snakes from a close distance and come off without a bite or fear in the heart, you are lucky. But this is pretty much not about you. It is about the class these animals and their kind represents. They are reptiles.
Reptiles have been an evolutionary grade of animals and comprise even some of the extinct mammals. The validity of this class is not supported universally in scientific circles because of the evolutionary history they carry with themselves. The study of reptiles, historically combined with that of amphibians, is called herpetology.
The Carboniferous period witnessed an evolution from some amphibians which could adapt to life on dry land. That was the beginning of reptiles. It was around 315 million years ago. Reptiles are now citizens in every country except the continent Antartica for obvious reasons. The living subgroups recognised are:
- Testudines (turtles, terrapins and tortoises): approximately 400 species
- Sphenodontia (tuatara from New Zealand): 1 species
- Squamata (lizards, snakes, and worm lizards): over 9,600 species
- Crocodilia (crocodiles, gavials, caimans, and alligators): 25 species
Reptiles have bodies like snakes or have four limbs which fail to provide "ground clearance" to their bodies. Unlike other four limbed creatures, reptiles have their bodies at not a great distance from the ground. As amniotes, reptile eggs have membranes surrounding them for protection. This also helps them adapt to reproducing on dry land.
The first of reptiles was a creature biologists term Casinera. A series of footprints from the fossil strata of Nova Scotia dated to 315 Ma show typical reptilian toes and imprints of scales.
It was a small, lizard-like animal, about 20 to 30 centimetres (7.9 to 11.8 in) long, with numerous sharp teeth which indicated an insectivorous diet.