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Reptiles Evolution of Reptiles Two major forces that lead to the transition of “full-time” life on land: 1. Increased competition for food and space in the water 2. Little competition for insects and plants on land Reptiles evolved from Cotylosaurs. They looked like small lizards and were successful due to the numerous insects on land which they ate. Cotylosaurs evolved into many new types of carnivorous reptiles including the thecodonts that later developed into the crocodiles, dinosaurs and the bird-like reptiles. What happened to the dinosaurs??? Adaptations to life on land: 1. Amniote egg- allowed reproduction completely on land. The egg has a protective membrane (chorion) and leathery, porous shell for gas exchange and holds in moisture. The internal aquatic environment enables embryos to survive on dry land. The amnion surrounds and encloses the embryo. The allantois stores waste. The yolk sac provides a food supply. Reptiles and Birds Adapt to land cont. Reproduction: Sexes separate-Fertilization internal and water is not needed to transport sperm to egg. Most reptile eggs are buried and the sun incubates them. After laying their eggs, most females leave them alone to hatch. Parthenogensis – females reproduce with out males (6 families of lizards; one snake species). No males exist. 2. Waterproof skin- Dry scales or plates made of keratin protect the body from water loss and rough environments. They can live in harsh conditions. Shed skin to grow. 3. External structural adaptations - limbs have claws to help in climbing and digging, etc. Some possess suction cups for climbing. Snakes lack limbs, but have a welldeveloped skeletal and muscle system to aid in locomotion. 4. Respiration and circulation Reptiles depend on lungs (full time) for gas exchange, ribs/body wall move posterior causing neg. pressure for air to move in; anterior movement; air moves out. A reptile’s lungs have a large surface area. Have a complex circulatory system ( 3-or 4 chambered heart) Most reptiles have a 3-chambered heart: two separate atria and one ventricle. The single ventricle pumps two batches of blood, some blood goes to the lungs to get oxygen, some blood with oxygen goes to body. Partial division of ventricle. Crocodilians have 4-chambered heart with two separate ventricles. Feeding and Digestion Most reptiles are carnivores, but some are herbivores. Many have small (backwards pointing) teeth to hold prey while swallowing. To make it easier to swallow prey whole, snakes have loosely jointed jaws that can spread apart and unhinge (kinetic jaws) to take in their food. Mouth esophogus stomach small intestine large intestine cloaca Excretion Kidneys filter the blood to remove waste products. Kidneys produce Uric acid, which can be stored in a paste-like form in the bladder. This dry waste enables reptiles to conserve water (water is pulled out of the waste in cloaca or bladder) and maintain homeostasis in their bodies. In some species, water can also be stored when available in the bladder or under the skin to be reabsorbed later, when water is scarce. (chuckwallas) Some have salt glands below the eyes to get rid of excess salt (marine iguanas) The Brain and Senses Vision is the main sense in most reptiles. Some reptiles have tympanic membranes and others detect vibrations through their jaw bones. In snakes, Jacobson’s organs in the mouth are used to sense odors. Temperature Control Reptiles are ectotherms and regulate their body temperatures by basking in the sun for warmth or burrowing in the ground to cool off. Metabolism increases as the body temp. Increases, thus increasing their activity. Movement Some reptiles move with limbs sprawled to their sides and push against the ground. Crocodiles have limbs rotated further under the body and can bear more weight and move faster. Orders of Modern Reptiles 1. Rhynchocephlia- tuatara 2. Chelonia-turtles and tortoises 3. Crocodilia-crocodiles, alligators, camains, gharials (gavials) 4. Squamata-lizards and snakes 1. O. Rhynchocephlia It has one “ancient” species living today, the tuatara. It is also called the living fossil since its order is so old. They are native to New Zealand and resemble a large lizard. It has a parietal eye, which is an eye covered by a thin layer of scales. (lens, nerve and retina) It is believed to help detect sunlight and keep the tuatara from overheating. They have two rows of teeth on upper jaw. Parietal eye 2. O. Chelonia - The turtles and tortoises. Turtles are aquatic and tortoises are terrestrial Turtles are streamlined for the water and tortoises have a large dome for protection. They have not change much in 200 million years, since they are successful due to the protective shell. The shell is either covered with bony plates or leathery skin. It has two parts: carapace ( top) and the plastron ( bottom). 3. O. Crocodilia - Crocodiles, alligators, caimans, and gavials (gharials) They have changed very little over the last 200 million years. They are mostly nocturnal and hunt by “stealth”. They are carnivorous and hunt with the eyes and nostrils out of the water, while lying submerged. Parental care is usually not present, but some species have been known to carry young from the eggs to the water. Caimans are native to Central America and Gavials eat fish in India and Burma. Crocodiles are found in Africa, Asia and the Americas. Alligators are found in Florida and China. Crocodiles and Alligators Crocodilians have a four-chambered heart which delivers oxygen more efficiently. Crocodiles have a long snout, sharp teeth, and powerful jaws. Alligators generally have a broader snout than crocodiles. 4. O. Squamata- the lizards and snakes. They have a lower jaw which does not join directly to the skull and have paired reproductive organs in the males. They live on every continent except Anartica and live in any type of habitat. Only two lizards are venomous. (Gila monster and beaded lizard). They eat insect and other small animals. They can change colors to match their background. They can lose their tails to escape predators and regenerate a new one ( Autonomy). They can fend off enemies with displays (horned lizards). Lizards usually have moveable eyelids, a lower jaw with a moveable hinge joint, and tympanic membranes. Snake external anatomy • Snakes probably evolved from lizards that lived above the ground and began to burrow as protection. Natural selection leg to lizards without legs to move through burrows better. Lack moveable eyelids and tympanic membranes. Snake facts: 1. Movement - 100-400 vertebrae with ribs make this possible. This provides a great frame for muscles. Skin and scales also aid movement or undulation. Three types of movement in snakes: a. Lateral- most common, head is moved from side to side and a wave of muscular contraction follows. (s-path, force on the sides) b. Rectilinear- force is on the belly scales or scutes which catch on bark or surface area. Resembles caterpillar movement. C. Sidewinding - done in the desert (sand) where traction is poor. A whip-like motion of the head slings the body to the side to move. Snake internal anatomy 2. Feeding - They are carnivores, but lack many good senses to hunt. They locate prey with Jacobson’s organ - two pits on the roof of the mouth which pick up chemicals from the tongue. It uses this method to stalk prey using a chemical trail. Prey are killed using constriction or venom. They then can swallow the animals whole. To do this, they thrust their windpipe into the mouth in order to breath while swallowing such a large meal and have loosely-jointed jaws. Most venom is injected using hypodermic-like fangs in the front, but some have back fangs. Two types of venom: A. Hemotoxins - proteins that destroy red blood cells and the platelets in blood. B. Neurotoxins - disrupt nerve pathways which control heart and lung functions. 3. Defense - by hiding, camouflage or warning of danger (rattles). 4. Pit vipers- find prey using heat (have pits on the side of her head) Chapter 29 Reptiles and Birds Chapter Diagnostic Questions Which is not an accurate description of a snake’s feeding methods? A. carnivorous B. tongue assists in swallowing C. venom paralyzes and digests D. skull bones and jaw joined loosely Chapter 29 Reptiles and Birds Chapter Diagnostic Questions Which is not a feature of lizards? A. tympanic membrane B. lack of moveable eyelids C. claws D. hinged lower jaw Chapter 29 Reptiles and Birds 29.1 Formative Questions Which animal does not have an amnion that surrounds its developing embryo? A. hawk B. human C. salamander D. squirrel Chapter 29 Reptiles and Birds 29.1 Formative Questions What does a snake detect with its Jacobson’s organs? A. heat B. odors C. sounds D. visual images Chapter 29 Reptiles and Birds 29.1 Formative Questions Which term describes the way reptiles maintain their internal temperature? A. ectothermic B. exothermic C. homeodermic D. thermodermic Chapter 29 Reptiles and Birds 29.1 Formative Questions What do snakes use for hearing? A. carapace B. jaw bones C. plastron D. tympanic membranes Chapter 29 Reptiles and Birds 29.2 Formative Questions How do birds maintain body heat? A. amnionically B. externally C. internally D. superficially Chapter 29 Reptiles and Birds 29.2 Formative Questions What organ in birds reabsorbs water from uric acid? A. cloaca B. bladder C. kidney D. pancreas Chapter 29 Reptiles and Birds 29.2 Formative Questions What is the term that means “to maintain favorable conditions for hatching”? A. gestation B. incubation C. maturation D. pregnancy Chapter 29 Reptiles and Birds Chapter Assessment Questions What is the function of Jacobson’s Organs? A. feeding B. breathing C. ejecting venom D. sensing odors Chapter 29 Reptiles and Birds Chapter Assessment Questions Which reptile mother can keep its eggs inside its body until they hatch? A. turtle B. crocodile C. snake D. tuatara Chapter 29 Reptiles and Birds Standardized Test Practice Which is a key adaptation that enables reptiles to live on land? A. Eggs have shells. B. Eggs are fertilized internally. C. Eggs are released in large numbers. D. Eggs hatch outside the female’s body. Chapter 29 Reptiles and Birds Standardized Test Practice Which structure makes the reptile heart more efficient than the heart of amphibians? Chapter 29 Reptiles and Birds Standardized Test Practice Which membrane contains food that provides nutrition to the embryo? Chapter 29 Reptiles and Birds Standardized Test Practice How does the cloaca enable reptiles to maintain homeostasis? A. It filters blood to remove waste. B. It reabsorbs water and minerals. C. It secretes hormones and enzymes. D. It improves gas exchange in the lungs. Chapter 29 Reptiles and Birds Standardized Test Practice Why do birds have a large cerebellum in their brain? A. to control behavior B. to coordinate visual input C. to sense tastes and smells D. to carry out complex movement Chapter 29 Reptiles and Birds Glencoe Biology Transparencies Chapter 29 Reptiles and Birds Image Bank Chapter 29 Reptiles and Birds Image Bank Chapter 29 Reptiles and Birds Vocabulary Section 1 amnion amniotic egg Jacobson’s organ carapace plastron Chapter 29 Reptiles and Birds Vocabulary Section 2 endotherm air sac feather incubate contour feather preen gland down feather sternum Chapter 29 Reptiles and Birds Animation Amniotic Egg Flight Visualizing Feeding and Digestion