Reptiles Chapter 41 Table of Contents Section 1 Origin and Evolution of Reptiles Section 2 Characteristics of Reptiles Section 3 Modern Reptiles

Section 1 Origin and Evolution of Reptiles Chapter 41 Objectives Summarize the factors that led to the rise of reptiles as the dominant land vertebrates. Identify three factors that contributed to the success of dinosaurs. Compare two hypotheses to explain the extinction of the dinosaurs. Identify examples of the four modern orders of reptiles. Describe three characteristics of modern reptiles that make them well adapted to life on land.

Section 1 Origin and Evolution of Reptiles Chapter 41 History of Reptiles Pangaea (the supercontinent formed by the joining of all of Earth’s land masses) had a drier interior climate than the coastal regions. Reptiles were well suited to dry climates.

Section 1 Origin and Evolution of Reptiles Chapter 41 History of Reptiles, continued The Mesozoic era is often called the Age of Reptiles. Reptiles flourished due to: An abundance of food A dry climate A mass extinction of other species

Chapter 41 Click below to watch the Visual Concept. Visual Concept Continental Drift (Pangaea) Section 1 Origin and Evolution of Reptiles

Chapter 41 Evolution of Dinosaurs Early in the Mesozoic era, Pangaea started to break apart. The climate of the land masses started to change. Some species of reptiles could not adapt and became extinct. Other species flourished.

Chapter 41 Breakup of Pangaea Section 1 Origin and Evolution of Reptiles

Chapter 41 Evolution of Dinosaurs, continued The evolution of reptiles has been marked by three mass extinction events, shown to the right.

Section 1 Origin and Evolution of Reptiles Chapter 41 Evolution of Dinosaurs, continued Triassic Dinosaurs The oldest known dinosaur fossils date from the early Triassic period, about 235 million years ago. These dinosaurs were small and carnivorous.

Section 1 Origin and Evolution of Reptiles Chapter 41 Evolution of Dinosaurs, continued Several factors contributed to the success of dinosaurs: Legs positioned under the body made them faster and more agile than other reptiles. Dinosaurs were well adapted to dry conditions. A mass extinction at the end of the Triassic period reduced competition.

Section 1 Origin and Evolution of Reptiles Chapter 41 Evolution of Dinosaurs, continued Jurassic and Cretaceous Dinosaurs The Jurassic period is called the golden age of dinosaurs. Jurassic dinosaurs included the giant sauropods, carnivorous theropods, and large herbivores like triceratops.

Section 1 Origin and Evolution of Reptiles Chapter 41 Evolution of Dinosaurs, continued Dinosaur Diversity Dinosaurs were not limited to terrestrial habitats. Some dinosaurs, such as pterosaurs, flew. Others, such as ichthyosaurs, inhabited the oceans.

Section 1 Origin and Evolution of Reptiles Chapter 41 Extinction of Dinosaurs Dinosaurs became extinct about 65 million years ago. Evidence suggests that environmental conditions over many years endangered dinosaur survival. Either a single asteroid or multiple asteroid impacts might have triggered a mass extinction event that killed the dinosaurs.

Chapter 41 Click below to watch the Visual Concept. Visual Concept Mass Extinction Section 1 Origin and Evolution of Reptiles

Chapter 41 Success of Reptiles There are four modern orders of reptiles: Chelonia (turtles and tortoises) Crocodilia (alligators and crocodiles) Squamata (snakes and lizards) Rhynchocephalia (tuataras)

Chapter 41 Phylogenetic Diagram of Reptiles, Birds, and Mammals Section 1 Origin and Evolution of Reptiles

Chapter 41 Success of Reptiles, continued Three characteristics contribute to the success of reptiles on land: The amniotic egg Watertight skin Efficient respiration and excretion

Section 1 Origin and Evolution of Reptiles Chapter 41 Success of Reptiles, continued The amniotic egg: contains a large amount of yolk which nourishes the developing embryo is usually surrounded by a leathery or hard shell within which the embryo develops the embryo is surrounded by several membranes which protect the embryo and exchange gases and wastes

Section 1 Origin and Evolution of Reptiles Chapter 41 Success of Reptiles, continued Parts of the amniotic egg: amnion - the thin membrane including the fluid in which the embryo floats yolk sac - encloses the yolk, the fat-rich food supply for the developing embryo allantois - stores the nitrogenous wastes produced by the embryo chorion - surrounds all other membranes and helps protect the developing embryo albumen - fluid containing protein and water needed by the embryo

Chapter 41 Click below to watch the Visual Concept. Visual Concept Amniotic Egg Section 1 Origin and Evolution of Reptiles

Chapter 41 Click below to watch the Visual Concept. Visual Concept Parts of an Amniotic Egg Section 1 Origin and Evolution of Reptiles

Chapter 41 Success of Reptiles, continued Watertight skin Amphibians are able to exchange gases and water through their skin. As a result, they risk dehydration through evaporation and must live in moist environments. Reptiles have thick, dry, scaly skin that prevents water loss. As a result, they are able to live in dry environments. The scaly covering of reptile skin is made of keratin, a tough fibrous protein that makes up scales, hair, and fingernails.

Chapter 41 Click below to watch the Visual Concept. Visual Concept Comparing Amphibian and Reptile Skin Section 1 Origin and Evolution of Reptiles

Chapter 41 Success of Reptiles, continued Respiration and excretion Modern reptiles have developed efficient respiratory and excretory systems that help them conserve water. Respiratory organs (lungs) located inside the body reduce water loss through evaporation. Nitrogenous wastes secreted in the form of uric acid, which requires little water for dilution, allows reptiles to lose only small amounts of water in their urine.

Chapter 41 Key Features of Reptiles Section 1 Origin and Evolution of Reptiles

Chapter 41 Click below to watch the Visual Concept. Visual Concept Characteristics of Reptiles Section 1 Origin and Evolution of Reptiles

Section 2 Characteristics of Reptiles Chapter 41 Objectives Identify advantages associated with the structure of a reptile’s heart. Describe the respiratory system of reptiles. Describe four methods reptiles use to sense their environment. Explain how reptiles regulate their body temperature. Compare oviparity, ovoviviparity, and viviparity as reproductive strategies.

Section 2 Characteristics of Reptiles Chapter 41 Circulatory System The reptile circulatory system consists of two loops: Pulmonary loop - carries blood from the heart to the lungs and then back to the heart Systemic loop - carries blood from the heart to the body and then back to the heart

Section 2 Characteristics of Reptiles Chapter 41 Circulatory System, continued Most reptiles have a three-chambered heart. The single ventricle is partially divided by a wall of tissue called a septum. Reptiles can divert blood from the lungs to conserve energy and warm their bodies. Crocodiles have a four-chambered heart.

Chapter 41 Turtle Heart Structure Section 2 Characteristics of Reptiles

Chapter 41 Click below to watch the Visual Concept. Visual Concept Reptile Heart Section 2 Characteristics of Reptiles

Chapter 41 Respiratory System The lungs of reptiles are large, and the lining may be folded into numerous small sacs called alveoli that increase the internal surface area. Reptiles inflate their lungs by expanding their ribs. This lowers pressure in the chest cavity and draws air in. When the ribs relax, air is forced out.

Chapter 41 Click below to watch the Visual Concept. Visual Concept Alveolus/Alveoli Section 2 Characteristics of Reptiles

Chapter 41 Nervous System A reptile’s brain has a large cerebrum, a well- developed olfactory lobe, and large optic lobes.

Section 2 Characteristics of Reptiles Chapter 41 Nervous System Reptile senses: Sight - Reptiles have large, well-developed eyes. Hearing - Sound waves strike the tympanum (eardrum) and are transmitted by the columella to the inner ear. Vibrations - Snakes lack a tympanum and can sense only low-frequency sounds and ground vibrations. Smell - Smell is important for most reptiles. Snakes have a special structure called the Jacobson’s organ, located in the roof of the mouth, that also detects odors. Heat detection - Pit vipers have a heat-sensitive pit below each eye that detects prey.

Section 2 Characteristics of Reptiles Chapter 41 Thermoregulation The control of body temperature is called thermoregulation. All living reptiles are ectotherms. Ectotherms warm their bodies by absorbing heat from their environment. Endotherms generate heat internally to maintain their body temperature.

Section 2 Characteristics of Reptiles Chapter 41 Thermoregulation, continued Advantages and limitations of ectothermy: Ectotherms have a slow metabolism and require very little energy. They need about one-tenth as much food as an endotherm of the same size. Ectotherms cannot live in very cold climates. Ectothermic metabolism cannot provide enough energy for sustained exertion.

Chapter 41 Changes in Lizard Body Temperature Section 2 Characteristics of Reptiles

Chapter 41 Click below to watch the Visual Concept. Visual Concept Comparing Endotherms and Ectotherms Section 2 Characteristics of Reptiles

Chapter 41 Reproduction and Parental Care There are three patterns of reproduction among reptiles: Oviparity - Eggs are laid in a tough protective shell. Ovoviviparity - Eggs have shells but develop within the female’s body. Viviparity - Eggs have no shells, develop within the female’s body, and are nourished through a structure called the placenta.

Section 2 Characteristics of Reptiles Chapter 41 Reproduction and Parental Care, continued Many species of reptiles provide no parental care for their young. Some species of lizards and snakes guard and warm the eggs until they hatch. Crocodiles and alligators provide the most parental care of any reptile. They build a nest, guard the nest, and carry the hatched young to the water. A mother crocodile may protect her young for a year or more.

Chapter 41 External Structures of a Timber Rattlesnake Section 2 Characteristics of Reptiles

Chapter 41 Section 2 Characteristics of Reptiles Internal Structures of a Timber Rattlesnake

Section 3 Modern Reptiles Chapter 41 Objectives Compare the anatomy of turtles with that of other reptiles. Describe the structure that allows crocodilians to swallow prey under water. Explain three antipredator defenses of lizards. Describe two ways snakes subdue their prey. Identify two reasons that tuataras are rarely seen.

Section 3 Modern Reptiles Chapter 41 Order Chelonia Chelonia includes turtles and tortoises. Turtles generally refers to chelonians that live in water. Tortoises generally refers to chelonians that live on land. Turtles and tortoises have a shell made out of bony plates. The carapace is the top part of the shell. The plastron is the lower part of the shell. The vertebrae and ribs are fused to the interior surface of the carapace.

Section 3 Modern Reptiles Chapter 41 Order Crocodilia Crocodilians are large, aquatic or semiaquatic carnivores. Order includes crocodiles, alligators, caimans, and gavials. A valve in the oral cavity covers the esophagus and windpipe, allowing crocodilians to capture and swallow prey underwater.

Section 3 Modern Reptiles Chapter 41 Order Squamata Lizards Most lizards rely on speed, agility, and camouflage to elude predators. Some lizards can detach their tail to distract predators. This ability is called autotomy.

Section 3 Modern Reptiles Chapter 41 Order Squamata, continued Snakes Some snakes kill their prey by wrapping their body around the prey and suffocating it. This is called constriction. Other snakes kill their prey by injecting venom. Prey must be swallowed whole. A snake’s jaw and skull are joined by a ligament that allows the snake’s head to stretch around its prey.

Section 3 Modern Reptiles Chapter 41 Order Squamata, continued Snakes can inject venom in three different ways: Snakes may have grooved fangs at the back of the mouth that guide poison into puncture. Elapid snakes inject poison through two small, fixed fangs in the front of the mouth. Vipers inject venom through large, hinged fangs in the front of the mouth.

Chapter 41 Click below to watch the Visual Concept. Visual Concept Anatomy of a Snake Section 3 Modern Reptiles

Chapter 41 Order Rhynchocephalia The order Rhynchocephalia contains only the tuataras, iguana-like reptiles with a spiny crest down their backs. Tuataras hide in burrows during the day and feed at night. The arrival of humans and new predators in New Zealand has reduced the number of tuataras.

Chapter 41 Click below to watch the Visual Concept. Visual Concept Types of Reptiles Section 3 Modern Reptiles