Reptiles and their characteristics (2nd Edition)

thank you [Music] the reptiles living today are the survivors of a momentous change that took place in the distant past dinosaurs and other ancient reptiles were once the dominant form of animal life on the Earth [Music] but the long age of reptiles came to a sudden end more than 70 million years ago all of the dinosaurs and many other reptile species have disappeared and yet even though their numbers have declined the reptiles of our time can be found in almost every type of environment on the Earth [Music] we classify the living reptiles into five groups the rare tuatara the lizards snakes Turtles and crocodilians a group that includes alligators as well as crocodiles the reptiles are part of a major division of animal life called vertebrates animals with backbones some of the vertebrates are classified as warm-blooded animals birds and mammals normally maintain a constant high body temperature using energy from the food they eat all of the other vertebrates are classified as cold-blooded animals that includes fish and amphibians as well as reptiles like other cold-blooded animals reptiles have a body temperature that varies with the temperature of their surroundings a repto like this lizard can use the heat from sunlight or from warm ground to raise its body temperature and then to keep from becoming too hot it crawls into the shade [Music] after basking in the sunlight alligators and some other reptiles cool themselves by moving into the water others like this snake will burrow into the ground to find a cooler place [Music] in cooler weather reptiles and other cold-blooded animals become less active as their body temperature Falls and during the coldest months many reptiles become completely inactive some find shelter beneath the ice-covered surface of a pond a turtle can absorb some dissolved oxygen through its skin enough to survive in this inactive state other reptiles like these fox snakes bend the winter in a protected place on land many reptiles including alligators and crocodiles are found only in tropical and subtropical climates where they can be active the year round but other reptiles can be found in almost every type of climate region on every continent except Antarctica in the long history of vertebrate life reptiles were the first true land animals they were the first of the vertebrates to lay their eggs on land their eggs have a tough protective covering that keeps them from drying out even when warmed by the Sun [Music] and all reptiles are born with lungs used for breathing air that's another way that they're different from older types of vertebrate animals amphibians also have lungs but only in the adult stage a female amphibian must lay her eggs in water because when the eggs hatch the young amphibians have gills and they breathe oxygen dissolved in water [Music] each female amphibian lays thousands of eggs that's important for the survival of the amphibian species because most of the eggs and most of the young will be eaten by predators [Music] by contrast reptiles don't lay nearly as many eggs a female lizard usually lays only about a dozen eggs at a time other reptiles may lay as many as a hundred but that's still much less than the thousands laid by a fish or an amphibian foreign s are laid it's possible for a reptile species to survive because eggs laid on land can be better protected than those laid in water [Music] there are some snakes that don't lay eggs at all young garter snakes were born directly from their mother's body but most young reptiles are hatched from eggs eggs that have a tough protective covering and are laid on land that's one of the adaptations that make it possible for reptils to survive even in very dry climates but there's another adaptation that's equally important the skin of a reptile forms a tough dry covering on most reptiles the outer layer of skin is molded into a series of separate scales on a turtle the skin is composed of larger bone-like scales that are fused together to form a rigid shell whether it's the shell of a turtle or the scales of other reptiles the tough dry covering helps to reduce the evaporation of body fluids and because of this many kinds of reptiles can be found in the hot dry climate regions of the world the tough watertight body covering is a characteristic that all reptiles have in common but each of the five groups of reptiles also has its own special characteristics the first group includes only one species the Tuatara found only in New Zealand the Tuatara is sometimes called a living fossil because its internal body structure is much the same as that of its ancient relatives that disappeared millions of years ago reptiles in the second group the lizards are very different from their ancient relatives in their skeletal structure and reproductive organs there are about three thousand species of lizards living in many different environments around the world the anole is a type of lizard that lives in forested regions it has a remarkable ability to change its skin color an ability that it shares with the chameleon another type of lizard here the color of the anole Blends closely with the tree trunk but when this anole moves to a leafy Branch its color changes within a minute or two that happens because the new location is slightly different in temperature and light intensity the color of the anole serves as a form of camouflage allowing it to hide from predators [Music] another kind of defense is provided by the long spines that extend from the body of this reptile it's often called a horned toad but it's really a horned lizard it lives in the desert thriving and scorching heat and dry air conditions that would quickly kill a toad or any other amphibian the horned lizard feeds on insects capturing them with its long sticky tongue [Music] another kind of desert lizard is the Gila monster which lives in Mexico in the southwestern United States gila monsters are the world's only poisonous lizards snakes are closely related to lizards the most obvious difference is that snakes have no legs most snakes move by bending the body into a series of s-shaped Curves and pushing against the ground from the back of each curve they gain traction from a row of large scales on the underside of the body scales act something like the cleats on a tractor and yet for most snakes movement on loose sand is still difficult but not for The Sidewinder rattlesnake it gains traction on Sand by looping its body and moving sideways there are several species of rattlesnakes and all of them are poisonous usually but not always they will make the rattling sound before striking but most snakes are not poisonous and we actually benefit from the feeding habits of most of them they help to control mice insects and other pests the structure of a snake's jaw allows for a very wide opening of the mouth and a snake can swallow its food whole some snakes respond to Danger by playing dead [Music] when the danger is passed the snake becomes active again snakes can be found in many different environments but the reptiles in another group the alligators and crocodiles live only in warm climates and always in or near water even with the body almost entirely submerged they're able to breathe normally because their nostrils are still above the surface alligators and crocodiles are very much alike but an alligator can be identified by its rounded nose and dark brownish color while a crocodile is greenish gray and has a pointed nose the crocodilians are the longest of All Reptiles some grow to a length of more than 20 feet or more than six meters reptiles in the fifth group The Turtles may also be very large the tortoises of the Galapagos Islands May weigh more than 400 pounds more than 180 kilograms but the largest Turtles are those that live in the ocean some of them weigh as much as three quarters of a ton in spite of their great weight they can move around easily because the water supports them [Music] it's only when the females go ashore to lay their eggs that their weight makes movement difficult oh the sea turtles are among the largest of all living reptiles but most Turtles are much smaller some grow to a length of only about four inches about 10 centimeters the painted turtle lives in the fresh water of a pond or stream and on the land nearby a box turtle is usually found on land but it may go into the water to cool itself and some turtles like the desert tortoise live all of their lives on land [Music] Turtles and other reptiles are able to survive in dry climates because of their hard protective skin covering and also because their eggs are laid on land reptiles are no longer the dominant form of animal life on the Earth but even though many species have disappeared others have survived continuing their long history that stretches back more than 300 million years [Music] oh [Music]