What is A Reptile? (1961)

reptiles are the first true land vertebrates animals with backbones in early prehistoric times animal life first lived in the water there were hosts of fishes then some fish-like creatures the amphibians began moving out on land but their jelly-like eggs still had to be hatched in water today's amphibians such as the salamander belong Midway between the fishes and the reptils none of the amphibians move very effectively on land all must go to water to lay eggs and the lung development of amphibians is barely adequate to maintain animals on dry land the Frog's moist skin supplements respiration all reptiles have lungs sufficiently well developed to make air breathing on land practical in contrast with amphibians reptiles have developed better limbs for Locomotion on land All Reptiles too have waterproof skin this helps make possible the broad distribution of reptils over much of the Earth contrary to popular opinion reptils are not slimy to the touch but the main adaptation to land reproduction is the development of the land egg the land egg contains a liquid medium for the embryo along with space for waste products and food the amnon makes this possible the liquid medium is contained within a sack the amnon waste products are put into another sack the Alano which also carries blood vessels to the Shell for the exchange of gases food is contained in the yolk sack the chonic membrane plus the shell enclose the embryo and all the other membranes in this film we will see some of the many ways in which this highly developed class of animals the reptiles demonstrate a large degree of adaptive radiation this is thought to be one of the first reptils during the age of reptils there were many strange and mighty creatures some reptiles lived on land some in water and some flew then many of the principal types of reptiles died out only their fossil skeletons and Footprints remain some of the Lush jungles and swamps in which the dinosaurs left their Footprints have become the rock floors of barren desert lands five kinds of reptiles remain on Earth lizards Turtles the Tara the crocodilians and the snakes all reptiles have certain characteristics in common they have well-developed tongues which some can extend and retract their skin is generally covered with scales they breathe through their lungs are coldblooded and their body temperature varies according to their environment here the cold of a freezer has been used to slow the action of a snake in warmer surroundings normal movement again takes place there are about 2,000 species of modern lizards most of them are harmless this hila monster from the American southwest is the only poisonous lizard in the world there are many useful and beautiful lizards they live in water in trees and on the ground this ground dwelling fence lizard is a member of the Iguana family in South and Central America the Flesh and eggs of various iguanas are considered Delicacies the monitor is one of the largest lizards this one is about 5 ft long this chameleon is from Africa the home of all the true chameleons its turreted eyes rotate independently the chameleon's long elastic tongue is sticky on the end it serves the chameleon well in Catching insects the main diet of most lizards the chameleon can change color this helps to hide it from its enemies the changing of color depends both on its environment and its condition other types of lizards that can change color like this American chameleon are named after the true chameleon of Africa the second reptile order contains the largest living reptiles the crocodilians and includes the American alligator which may grow to a length of 15 ft crocodilians spend some time on land but their real home is the water where they are strong and fast swimmers their powerful taals used to propel them sometimes serve as a means of Defense on land too the alligator can move rapidly crocodilians eat turtles fish and other animals found in or near the water the female alligator prepares a nest of decaying vegetation in which to lay her eggs she guards the nest until the young have hatched the crocodile looks like an alligator but crocodiles have a more pointed snout and are lighter in color crocodiles and alligators can open their mouths underwater without drowning because the air enters the nostrils and travels through the skull separated from the mouth cavity by a hard pallet and emerges in the back of the throat powerful jaws help the crocodile to defend itself and to catch and devour its prey sometimes crocodiles attack man but more often man attacks crocodiles crocodilian Skins are an important source of leather used in many manufactured products another reptilian order the two ataras has but one living species called the tuara found only in New Zealand it is the last survivor of a prehistoric group older than the dinosaurs the fourth reptilian order is that of the turtles and tortoises there are over 200 species they range in size from this tiny young mud turtle which weighs less than an ounce and is half an inch long to the huge galopagos land tortoise which often grows longer than 6 ft and weighs almost half a ton Turtles have no teeth their horny beaks are used for tearing they reproduce through eggs which usually have a leathery shell the painted turtle lives in or near fresh water while the Box tortoise lives on land a turtle's shell is part of its skeleton this Skeleton shows how the vertebrate skeleton has developed into this box-like covering in most tortoises the shell is high and arched some are even hinged underneath for complete closing of the Box this type of shell helps protect the tortoise's head and legs from enemies sea turtles and land turtles have returned to to the water their limbs have become paddles this is secondary Evolution this green turtle cannot hide inside its shell its shell is flat streamlined for swimming soft shell turtles have a leathery outer shell enclosing an inner bony shell turtles are widely used as food by humans and the shells of some turtles are made into useful objects the snakes a fifth order are probably the most misunderstood of the reptiles no order of animals is so widely disliked and feared there are about 2,000 species of snakes about oneir of these are poisonous the bite of only a few is fatal to man snakes live in water climb trees and dig big holes in the ground snakes have no external limbs a snake moves by means of the large scales on its bottom side called ventral plates as the snake moves from side to side these scales catch on to even minute projections and help to move the snake but the real power for movement is the muscular action of the loops bracing against obstacles on the ground which pushes the snake along snakes shed their skin as they grow the bright new skin shows the real beauty of the snakes markings snakes have no ears and no eyelids but the eye has a transparent cover which is shed each time the skin is shed the snake has a slender forked tongue but no vocal cords so the only sounds they make are by hissing vibrating their tails or rattles or making a rasping sound with rough scales some snakes catch their prey by injecting poison into their victims with fangs or teeth the Indian cobra's venom attacks the nervous system the American black snake died quickly after being struck by the Indian cobra the only member of the Cobra family found in North America is the pretty coral snake it too poisons its victims it feed feeds mainly on other snakes one other family of snakes in North America catches prey by poisoning the pit vipers they include the rattlesnakes the Copperheads the moccasins and others the name pit viper comes from the pit or depression on the head the pit contains a sense organ which detects heat the diamond back of the Southern United States is the biggest of the American rattlesnakes they sometimes grow over 8 ft long they will strike in self-defense when frightened or provoked when they strike Large Hollow fangs pierce the victim's flesh and inject the deadly venom it destroys the red cor pusles weakens the walls of blood vessels here we see the Venom being forced out by pressure of the human hand but most rattlesnakes seem to avoid danger if possible if they cannot flee they rattle their tails this warns the Intruder to beware the Venom of poisonous snakes is mainly a food Gathering device but is used in defense against enemies from which they cannot escape this Cog no snake is harmless but appears to be a good bluffer when approached it puffs up spreads its neck and Strikes at its enemies if this fails to frighten the enemy away it will turn over on its back and appear to play dead the aggressive King Snake feeds on many snakes including pit vipers such as the Mojave rattlesnake to whose poison the king snake is immune the king snake and others like this corn snake constrict their prey causing death by Suffocation before swallowing it whole the lower jaw bones of a snake are hinged in such a way as to permit the snake to open its mouth unusually wide and to swallow its food whole because of its elastic Jaws the snake can swallow victims that are bigger around than itself snakes benefit Man by helping to control insect and rodent pests they also provide skin Venom and food some snakes lay their eggs in leaves Hollow logs or other protected places and the eggs usually receive no care from the mother after being laid the young snakes hatch in about 6 to 8 weeks and must care for themselves as soon as they leave the egg the water snakes garter snakes pit vipers and others retain their eggs until they are hatched reptiles are an important part of the world in which we live most of them are useful to man some serve as food some help control insect and rodent pests others provide leather or medical products fear of harmless snakes is needless and most reptils are harmless poisonous ones should be recognized and avoided killing reptiles unnecessarily upsets the intricate balance that exists in nature the many different forms of reptiles that exist today are living evidence of the ability of this class of animals not only to survive but to develop widely varying forms in many parts of the world in this film we have seen seen examples that suggest the principal reason for the success of members of the class reptilia it is freedom from the necessity of spending a part of each life cycle in the water this is possible because of the evolution of the land egg waterproof skin and improved limbs