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Chapter 17 and 18 Notes, Reptiles and Amphibians. Characteristics of Class Amphibia. Most amphibians are tetrapods , meaning they have four limbs , but some are limbless . Amphibians have smooth, moist skin .
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Characteristics of Class Amphibia • Most amphibians are tetrapods, meaning they have four limbs, but some are limbless. • Amphibians have smooth, moist skin. • Amphibians respire by lungs, skin, and gills; either separately or in combinations. • Amphibians have a 3-chambered heart, with two atria and one ventricle. • Amphibians are ectotherms, meaning they require an external source of heat.
Caecilians: Order Gymnophiona (Apoda) • Caecilians have a long slender body that is limbless and they live in burrows. • Caecilians live in tropical regions. • Caecilian's eyes are small and they are almost completely blind. • Caecilians are carnivores that eat mostly worms and other invertebrates. • Fertilization is internal, but eggs are usually deposited in moist ground near the water.
Salamanders: Order Urodela (Caudata) • Salamanders are tetrapod amphibians with tails. • Most of the salamanders in North America are less than 6 inches (15 cm) long. • Some are much larger, like the giant Japanese salamander that can exceed 4-5 feet (1.5 meters). • Most salamanders have four equal-sized limbs set at right angles to their body. • Salamanders are typically carnivores that prey on worms, arthropods, and mollusks.
Frogs and Toads: Order Anura (Salientia) • Frogs and Toads lack tails as adults. • All frogs and toads bear a tail in the larva stage. • Frogs and Toads are adapted for jumping. • The name Anura means “without a tail” and Salientia means “jumping or leaping”. • Eggs of frogs and toads hatch into a tadpole, having a finned tail, internal and external gills, no legs, and tadpoles are herbivores.
Frogs and Toads: Order Anura (Salientia) • Adults are much different than the larval form. • After tadpoles go through metamorphosis, frogs and toads lose their tail and gills,develop legs, and become carnivores. • Frogs and Toads vary in size from the West African Goliath frog (30 cm long or 1 ft.), to some that are less than 1 cm in length. • The Goliath frog can consume rats and ducks.
Frogs and Toads: Order Anura (Salientia) • Frogs are found all over the world, but the majority of them are found in tropical regions. • Those that live in colder climates, hibernate in the winter. Some frogs hibernate in the soft mud of ponds and streams. • Terrestrial frogs, such as tree frogs, hibernate in the humus (leaf litter) of the forest floor. • Some can even withstand freezing temperatures by converting glycogen from their liver into glucose, which prevents ice-crystal formation.
Class Reptilia • Body is covered in scales made of keratin. • Most are tetrapods, some are limbless. • Respiration is by lungs, not by skin or gills. • 3-chambered heart in most, with the exception of the crocodilians which have a 4-chambered heart. • Ectothermic; body temperature is modified bybehavioral thermoregulation. • Fertilization is internal • Amniotic eggs covered with leathery shells with internal embryonic membranes.
Characteristics of Reptiles • Reptile scales are different than fish scales. • The scales on a reptile are made of keratin and are similar in material to mammal skin. • Reptile eggs are amniotic, meaning they have internal membranes, (like the chorion and allantois) which help exchange gas and remove metabolic waste. • The tough leathery shell also allows the eggs to be laid in dry terrestrial environments.
Characteristics of Reptiles • Reptiles have a double pump circulation with a systemic (body) and pulmonary (lungs) circulation. • Reptiles do not have completely separated ventricles, which causes partial mixing of deoxygenated and oxygenated blood. • Reptilian lungs are more efficient than amphibian lungs.Their rib cage can expand and contract, but, they lack a muscular diaphragm like mammals.
Turtles: Order Testudinata • The body of a turtle is enclosed in two shells; the dorsal shell called the carapace and the ventral shell called the plastron. The carapace is fused with the ribs and the vertebrae. • Shell provides protection for the head, arms, and legs, which can be retracted into the shell. • The turtle cannot expand the chest to breath so they use abdominal and pectoral muscles to draw air into the lungs.
Turtles: Order Testudinata • Turtles lack teeth, but they have beak-like jaws lined with tough plates made of keratin. • Turtles are almost completely deaf, but they have a good sense of smell and vision. • Turtles are oviparous, with internal fertilization. • All turtles, including marine forms bury their amniotic eggs in the ground. • Nest temperatures determine the sex of the turtles; low temperatures males, high temperatures females.
Turtles: Order Testudinata • Leatherback marine turtles can reach 2 meters in length and weigh up to 725 kg (about as heavy as a large moose at 1500 lbs) • Some land tortoises like the Galapagos Island tortoises can weigh several hundred kilograms. • Most tortoises are slow moving, moving only a few hundred meters per hour. • Their low metabolism may explain their longevity. Some living over 150 years.
Order Squamata: Lizards and Snakes • Approximately 95% of all known living reptiles belong in this order. • One feature of the order squamatathat has made them some of the most successful and diverse of all the reptiles is the kinetic skull. • The kinetic skull is an adaptation that allows the snout to be tilted upward, in order to capture and manipulate their prey and increase the force of the jaws.
Lizards: Suborder Sauria • Suborder Sauria (a suborder of the order Squamata) includes geckos, iguanas, skinks, and chameleons. • Most lizards are tetrapods, except for the glass lizards which are limbless. • Lizards have movable eyelids, snakes do not. • Lizards have rods and cones in their eyes which give them excellent daytime vision, except some nocturnal geckos that have only rods. • Most lizards have external ears, snakes do not.
Lizards: Suborder Sauria • Lizards are also well adapted to living in hot, arid climates like the desert. • Lipids (fats) in their skin minimize water loss. • Concentrated urine conserves water. • Some lizards, like the Gila monster of the southwestern U.S., store fat in their tails, which they use for an energy and water reservoir. • Ectotherms do not require as much energy to live as do endotherms.
Snakes: Suborder Serpentes • Snakes are limbless reptiles and they usually they lack pelvic and pectoral girdles. • Numerous vertebrae and ribsprovide support, protection, and more leverage for the muscles to increase efficiency in locomotion. • The kinetic skull enables snakes to swallow prey several times their size. • Snakes do not have movable eyelids, but they do have permanently covered transparent eyelids.
Snakes: Suborder Serpentes • Snakes do not have any external ears. • Snakes do have internal ears that can detect limited low frequency sounds. • Snakes are sensitive to ground vibrations. • Most snakes have relatively poor vision. • Some arboreal (tree-dwelling) snakes have excellent binocular(stereoscopic) vision, that is useful for tracking prey through branches.
Snakes: Suborder Serpentes • Probably the most advanced sensory organs used by snakes is called the Jacobson's organ, which is an organ that can detect chemicals in the air from a pair of pits that are found on the roof of their mouth. • The Jacobson's organs are lined with olfactory sensory neurons. • Their forked tongue, flicks the air to pick up scent molecules, which are carried to the Jacobson's organ.
Snakes: Suborder Serpentes • Most snakes kill their prey by grabbing it and swallowing it whole, but this can be dangerous. • Constrictor snakes, kill their prey first by constriction, then swallow the prey whole. • Some constrictors can swallow prey as large as deer, leopards, and even crocodiles. • The muscles of constrictors are very large, but, the large muscles slow them down. • So most constrictors wait and ambush their prey rather than seek out their prey.
Snakes: Suborder Serpentes • Other snakes kill their prey with venom before swallowing it whole. • Vipers (members of the Viperidae family) have large, movable fangs at the front of their mouths. • Elapids ; Cobras, mambas, and coral snakes (members of the Elapidae family) have permanently erect fangs. • Some vipers are called pit vipers because they possess special heat-sensitive pit organs on their heads that detect infrared heat produced by endotherms (warm-blooded animals).
