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Chapter 20 - Chapter 20 Amphibian and Reptilian Anatomy and...

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Chapter 20: Amphibian and Reptilian Anatomy and Physiology 1. What are the four orders of living reptiles? What are the three orders of amphibians? The class Reptilia comprises four orders: (1) Crocodylia (alligators and crocodiles), (2) Squamata (snakes and lizards), (3) Chelonian (turtles and tortoises), and (4) Rhyncocephalia (tuataras). The class Amphibia is made up of three orders: (1) Gymnophiona (caecilians), (2) Anura (frogs and toads), and (3) Caudata (salamanders and newts). 2. Define ectothermic. Amphibians and reptiles are commonly referred to as ectothermic or cold-blooded . Ectothermic animals are unable to generate body heat internally, therefore their body temperatures are dependant on environmental temperatures. 3. What is a “preferred optimal temperature zone”? An ectotherm’s ability to effectively thermoregulate is entirely dependant on access to temperatures within the animal’s preferred optimal temperature zone (POTZ), which is a range of temperatures in which the animal can perform all necessary metabolic functions. This principle becomes very important when maintaining herptiles in captivity. If not provided with an appropriate thermal gradient, it will not be able to thermoregulate efficiently. When provided with inappropriately low temperatures, ectothermic animals can suffer from digestive problems, immunosuppression and other disorders. If kept at temperatures that are too high, the animal is forced to maintain a high metabolic rate and may suffer from energy deficits. 4. How does an ectothermic animal maintain an appropriate body temperature? Ectothermic animals maintain their body temperatures in an appropriate range through a process called behavioral thermoregulation , which allows amphibians and reptiles to precisely regulate their body temperatures according to metabolic need. Movements within the thermal gradient of their habitat as well as postural changes enable herptiles to adjust their body temperatures as needed. For instance, many herptiles "bask" to elevate body temperatures and seek shade when they need to cool down. A snake trying to conserve body heat coils tightly to decrease surface area and consequently heat loss, whereas a hot snake uncoils to accomplish the opposite. Some animals can actually adjust the color and pattern of their skin to increase or decrease the absorption of thermal energy from the sun (for example, chameleons). 5. Ecdysis in reptiles is under the control of what hormone? Ecdysis is under the control of thyroid hormone. 6. What is a “drink patch”? A drink patch is an area of the skin with increased permeability. It is usually present on the ventral surfaces that most frequently come in contact with water. The extremely permeable nature of amphibian skin allows them to absorb all the water they need from the environment, thus amphibians do not drink.
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