Chapter 26 (Reptiles, Birds, and Mammals) Outline
I. Reptiles

A. Reptilian Adaptations to Terrestrial Life

· Reptilian skin is dry and covered with tough, hard, platelike scales.

· Reptilian skin is resistant to water loss because it contains large amounts of lipids and the protein keratin.

· Keratin is the tough, wear-resistant material that composes your hair and fingernails.

· Since the amniotic egg contains its own supply of water, reptiles need not travel to water to reproduce.

· In the hearts of all reptiles except crocodiles and alligators, the ventricle is partially divided by a wall of tissue that reduces the amount of blood mixing.

· In crocodiles, alligators, birds, and mammals, this portion is complete.

· The circulatory system of reptiles helps them meet the increased energy demands of an active lifestyle.

· Reptiles excrete nitrogenous waste as uric acid, a form that requires very little water from dilution.

· Reptile urine contains so little water it is paste rather than liquid.

· Lizards and other reptiles, such as snakes, raise their body temperature by absorbing heat from their surroundings.

· Reptiles are ectotherms - cannot regulate their body through metabolism. So their body temperature changes with the temperature of their surroundings.

· Birds and animals are endotherms – produce their body heat internally through metabolism and maintain their body temperature within narrow limits.

· Ectotherms are often called “cold-blooded” and this description is not accurate.

· Endotherms can sustain activity for longer periods of time than can reptiles and amphibians, but endothermy requires large amounts of food.

B. The Age of Reptiles

· The 1st reptiles evolved about 320 million years ago, when the world was entering the dry period.

· The period of reptile dominance, which lasted from 250 million to 65 million years ago, is called The Age of Reptiles.

· Two groups of retiles inhabited the ocean while the dinosaurs lived on land.

· Ichthyosaurs were fully adapted for an aquatic existence and resembled dolphins, having a pointed snout, streamline body, fins, and a flattened tail.

· The long necked plesiosaur had barrel-shaped bodies with paddle like fins.

· The plesiosaurs and ichthyosaurs probably fed on fish.

· Dinosaurs, meaning “terrible lizards” in Greek, evolved from retiles that were only 2ft to 3ft in length.

· Pterosaurs were the first vertebrates to fly, even before birds, by 75 million years.

· Pterosaurs were most likely active flyers, not merely gliders.

· One former popular hypothesis of the extinction of dinosaurs is that the Earth entered a time of significant cooling 65 million years ago. Thus, dinosaurs were unable to maintain sufficiently high body temperatures to survive.

· The most widely accepted hypothesis is that a large meteorite, about the time dinosaurs disappeared, struck the Earth.

· Scientists discovered a layer of iridium (an element very rare on Earth but common on meteorites) and bits of melting rock that exhibit stress fractures characteristics of blast damage.

C. The Survivors

· The mass extinction 65 million years ago spared four groups of reptiles: lizards and snakes, turtle and tortoises, crocodiles and alligators, and the tuatara.

· Of the four groups, alligators and crocodiles are the most closely related to dinosaurs.

· All turtles have a shell – composed of bony plates that are fused together.

· Turtles lack teeth but have a sharp beak.

· The tuatara is a lizard like reptile that closely resembles its relatives, the Rhynchocephalia, and is found only on a few islands near New Zealand.

· There are about 6,800 species of snakes and lizards, and they live on every continent except Antarctica.

· All snakes lack limbs, movable eyelids, and external ears.

· Snakes are carnivores and have jaws with 5 joints (humans have only one) allowing great jaw flexibility.

· Most lizards have four limb and external ears.

· Most species of lizards are carnivores, but a few are herbivores.

· Only two species of lizards are poisonous: the Gila monster of the southwestern United States and northern Mexico, and the Mexican beaded lizard of western Mexico.