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Ch. 31-1 - Reptiles. By: Brittnie Smithley, Manuel Gutierrez, and Candelaria Caiero. What Is a Reptile?. Basic body plan of a typical land vertebrate: Well-developed skull Backbone and tail Two limb girdles Four limbs.
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Ch. 31-1 - Reptiles By: Brittnie Smithley, Manuel Gutierrez, and CandelariaCaiero
What Is a Reptile? • Basic body plan of a typical land vertebrate: • Well-developed skull • Backbone and tail • Two limb girdles • Four limbs • A reptile is a vertebrate that has dry, scaly skin, lungs, and terrestrial eggs with several membranes.
A reptiles skin helps prevent losing the body’s water in dry environment but it doesn’t grow along with the rest of the reptile so they periodically shed their skin • Reptiles are widely distributed on Earth, the only places reptiles cannot live is in very cold areas.
Evolution of Reptiles • Reptiles evolved form amphibianlike ancestors • When swamps and lakes began to dry up and reduced the amount of available water to all the amphibians, the first great adaptive generation of reptiles began. • At the end of the Triassic period, more reptiles showed up as ….
DINOSAURS!!!!! • Mesozoic era often called the age of reptiles • Large aquatic reptiles swam in the seas, ancestors of turtles, crocodiles, lizards, and snakes populated many land habitats, and dinosaurs were EVERYWHERE! • Dinosaurs came in a wide variety but all either fit in the two major categories: • Ornithischia or “bird-hipped” • Saurischia or “lizard-hipped” Even though Ornithischia means bird-hipped, modern birds probably evolved from evolutionary lines of the Saurischia.
Forms and Functions • Most reptiles are used to a fully terrestrial life. Reptiles have well-developed lungs, double loop circulatory system, water conserving excretory system, strong limbs, and an internal fertilization. • Controlling bodytemperatures-Controlling body temperatures for active animals is an enormous asset. Most animals are ectotherms which means they rely on behavior to help control body temperature (Turtles and snakes are examples). To keep warm they bask in the sun during the day and to cool down they move to shade or go for a swim.
Feeding-Reptiles eat a wide range of foods. Iguanas are herbivores that tear plants into sheds and swallow the tough chunks. The long digestive system enables them to break down the material. A lot of reptiles are carnivores, such as snakes that eat small animals, bird eggs, or even other snakes, by grabbing them in their jaws and swallowing them as a whole. Crocodiles and alligators eat fish and some land animals. Most reptiles, though, eat insects. • Excretion-In some reptiles urine flows through the tubes directly to a cloaca like amphibians. In Others the urinary bladder stores urine before it expels from the cloaca. Their urine contains either ammonia or uric acid, reptiles that live in water excrete most of their nitrogenous wastes in forms of ammonia. Reptiles that live on land don’t excrete ammonia directly, they convert it into uric acid. It is less toxic than ammonia so it doesn’t have to be diluted so much. The excess water is absorbed in cloaca reducing the urine to crystals of uric acid forming a pasty white solid. When eliminating the wastes that contain water it can conserve water.
Respiration- The lungs of reptiles are spongy providing more gas exchange area than those of amphibian. A lot of reptiles have muscles around the ribs that expand the chest to inhale and collapse the cavity to force air out. many crocodiles have flaps of skin that separate the mouth from the nasal passages allowing them to breathe when their mouths are open. To exchange gases with the environment reptiles have 2 lungs but snakes only have one. • Circulation- Reptiles have a double loop circulatory system. 1 of the loops brings blood to and from the lungs and the other brings blood to and from the rest of the body. Their system contains 2 atria and 1 or 2 ventricles. Most have a single ventricle with a partial septum that helps separate oxygen-rich and oxygen-poor blood during this cycle. Crocodiles and alligators have the most developed circulatory system out of all reptiles.
Response- the pattern of the brain of a reptile is much like an amphibians except its cerebrum and cerebellum is larger compared to the rest of the brain. Reptiles that are active in the day have complex eyes and can see colors well. Snakes have a very good sense of smell compared to most reptiles, most reptiles have sensory organs on their roof of their mouths that detect chemicals when reptiles flick their tongues. Reptiles also have very simple ears, snakes sense vibrations in the ground through their skulls and they have an amazing ability to sense body heat in some of their prey. • Movement-reptiles have large strong limbs that enables them to walk run swim or climb. The legs are rotated under the body of some reptiles. Aquatic turtles have legs that have been developed into flippers since they live in water. Reptiles also have a backbone that helps them with their movement.
Reproduction-all reptiles reproduce by internal fertilization • male reptiles have an organ that allows them to deliver the sperm into the females cloaca. After fertilization, the females reproductive system covers the embryo with several membranes. • most reptiles lay eggs that develop outside the mothers body. Reptiles lay the eggs in nests, but some abandon the eggs while others guard them till they hatch then take care of them. Some are ovoviviparous and their babies are born alive. The shell and membranes of the egg create a safe environment in which the embryo can grow without drying out, this is called an amniotic egg. The four membranes of the embryo are amnion, the yolk sac, the chorion, and the allantoios.
Groups of Reptiles • The four surviving groups of reptiles are lizards and snakes, crocodilians, turtles and tortoises, and tuatara.
Lizards and Snakes • Modern lizards and snakes belong to the order Squamata, or scaly reptiles. • Most lizards have legs, clawed toes, external ears, and moveable eyelids, and snakes have no legs but can produce venom.
Crocodilians • Belong to the order Crocodilia • They are very protective of their young • They only live in the tropics and subtropics • Alligators and their close relatives live in only fresh water and are found almost exclusively in north and south America • Crocodiles may live in either fresh or salt water and are native to Africa, India, and Southeast Asia.
Turtles and Tortoises • Members of the order Testudines • Turtles live in water and tortoises live on land • They have a shell built into the skeleton consisting of 2 parts: a dorsal part, or carapace, and a ventral part, or plastron. The backbone forms the center of the carapace. • Instead of teeth, they have horny ridges on the upper and lower jaws.
Tuataras • The only surviving members of the order Sphenodonta • Found only on a few small islands off the coast of New Zealand • They resemble lizards, but are different from lizards in many ways • Lack external ears and have primitive scales • Have a legendary “third eye” which is part of a complex organ located on top of the brain. It can sense levels of sunlight, but its function is unknown.
Ecology of Reptiles • Many reptiles are in danger because their habitats have been, and are in the process of being destroyed. • In addition, humans hunt reptiles for food, to sell as pets, and for their skins.
