Chordata-Reptilia

Chordata- Reptilia By Krista Sabina

(MC)

African snake- this snake was so big that it scared the natives who were not scared of snakes(ZS)(17-18) Diagnostic Characteristics

Reptiles are characterized by several adaptations to denote their classification. One of these adaptations is scales instead of skin. These scales contain a protein called keratin which waterproofs their bodies and helps prevent dehydration. Reptiles can not breathe through the skin as amphibians; they must obtain oxygen though lungs. Reptiles are ectotherms, using the solar energy for heating their bodies and shade for cooling, allowing them to use less than 10% the calories from metabolic breakdown. The laying of amniotic eggs on land is another characteristic of the reptilian group. These eggs are fertilized internally. Some snake and lizard species are viviparous, having a placenta to give nourishment to the embryo. These characteristics define reptiles as a whole, but when they are further categorized more characteristics may be found.

Acquiring and Digesting Food

The reptiles of today are classified as carnivores and herbivores. Considering their low metabolic rate, the reptiles have evolved and adapted to compensate. These adaptations are most widely seen in snakes. Some of these adaptations are acute chemical sensors; tongue flicking that sends the scent of prey to the olfactory organs, and sensing ground vibrations aid snakes in tracking food sources. Also when acquiring food heat sensing organs help detect prey, especially at night. In snakes a ligament lower jaw and an expandable stomach, allows them to swallow their prey whole. Venomous snakes have sharp hollow or grooved teeth that allow them to inject poison into prey. Because of the low metabolic rate, snake and lizards can use sit and wait feeding and “bulk- eat”, using less energy output. Since the reptilia kingdom is quite diverse, there is not one shared digestive system among them. In snakes for example, the digestive system is composed of the esophagus which is adjacent to the air sacs of the pharynx or throat, stomach, small intestine, colon, and glands. The esophagus has very little muscle and food is moved to the stomach more by movement of the entire body. The junction between the esophagus and the stomach is not well defined, and the stomach itself is not very advanced. It is a short, with interior longitudinal folds to increase the surface area for digestion and absorption. The small intestine is a long tube that receives food from the stomach, absorbs nutrients from it, and transports it to the colon, or large intestine. The colon then carries the fecal matter to the cloacal opening where it is disposed. The cloaca is a common chamber, receiving products from the digestive, urinary, and reproductive systems. The pancreas, gall bladder and liver also assist with the digesting of food. The liver produces bile, the gallbladder stores the bile and then secretes it into the small intestine when needed, and the pancreas produces enzymes to help with digestion and also regulates blood sugar with the hormones it creates. (YA)(2)

This image demonstrates the positioning of various organs within the lizard. (LW) (12)

Sensing the Environment Creatures of the reptile classification breathe using lungs to obtain oxygen. Crocodiles and alligators have upturned nostrils. Snakes and lizards use nostrils to breathe air but also use tongue flicking to send odors to the olfactory organs that are found on the roof of the mouth. Lacking eardrums, snakes are sensitive to ground vibrations. Some poisonous snakes have heat detecting organs located between the eyes and nostrils. Vision in snakes varies; some are blind; some differentiate between light and dark and some can see but not very clearly. Compared to snakes, turtles and other reptiles are thought to have slightly better vision and be able to see a broader range of color. Lizards can change the shape of the lens inside the eye to focus on different objects. Snakes have very poor hearing and can only detect ground vibrations. Most reptiles have very low quality hearing. As oppose to humans, reptiles have interrelated senses of smell and taste. After tasting something, a reptile can convert that sense into a smell through Jacobson's organ. This organ is generally located at the roof of the mouth. (NG) Snakes do not have eyelids or eyelashes, so the brille (transparent eye covering) protects the eyes. Every time a snake sheds, they acquire a new brille. This means that if their eyes are scratched or damaged, they will be fixed the next time they shed. (13)(SM)

Locomotion Turtles and crocodiles have four limb used to move on land or through water. Snakes evolved from lizards. The snakes use lateral undulation for motion while lizards use a combination of both lateral undulation and the use of four limbs.

Land turtles have feet and claws, allowing them to walk. Whereas sea turtles have more paddle-like flippers with two claws, allowing easier swimming. (MLK) [|14]

"In concertina locomotion, the snake bends the body up like an accordian then lifts and straightens out the body to move forward. The crocodile, on the other hand, the low center of gravity causes it to bend in different ways as if it looks like its wobbling.This website explains a lot more of the different types of locomotion of various reptiles." [|5] [MS]

[|Snake Locomotion Youtube Video] (SI)(20) 

<span style="color: #4f6228; font-family: Algerian; font-size: 18pt; line-height: 115%; margin: 0in 0in 10pt;">Respiration <span style="color: #4f6228; font-family: 'Times New Roman','serif'; font-size: 14pt; line-height: 115%; margin: 0in 0in 10pt;">Using nostrils, reptiles use lung to acquire oxygen from the air. They can not use their skin as amphibian ancestors. Reptiles have a three-chamber heart with exception of the crocodile and alligators. The three -chamber heart has two arias and one ventricle. Crocodile and alligators have four chamber hearts where the oxygen rich blood can not mix with the oxygen poor blood. <span style="color: #4f6228; font-family: 'Times New Roman','serif'; font-size: 14pt; line-height: 115%; margin: 0in 0in 10pt;">"One of their major characteristics of reptiles is thoracic breathing. They breathe in by enlarging the thoracic cavity. Reptiles lack a diaphragm. Snakes and lizards expand their rib cage; turtles and crocodilians use movement of internal organs to create negative pressure to inhale. Thus reptiles "suck" air into their lungs, unlike amphibians which "force" air into their lungs. Reptile lungs are better developed than those of amphibians." (AK) (4) Many turtle species can have gas exchange across the wet surface of the **cloaca**, a cavity at the end of their digestive system that is used to excrete waste, and on the inside of the mouth. Most employ lungs that contain **alveoli**, which are small sacs that gather air and contain blood vessels to exchange oxygen with carbon dioxide. Most reptiles have an unusual breathing pattern of long pauses followed by inhalations and exhalations. Since constant lung ventilation is not necessary, the metabolic rate of reptiles is much smaller compared to that of birds and mammals. (DB) (23) An example of the respiratory system of a reptile. (RL)(22)

<span style="color: #4f6228; font-family: Algerian; font-size: 18pt; line-height: 115%; margin: 0in 0in 10pt;">Metabolic Waste Removal <span style="color: #4f6228; font-family: 'Times New Roman','serif'; font-size: 14pt; line-height: 115%; margin: 0in 0in 10pt;">Most reptiles expel uric acid through two small kidneys. Uric acrid is their primary way to dispose of their nitrogenous waste. It can be a semisolid paste for little water loss. Turtles are the exception. They excrete urea, a combination of carbon dioxide and ammonia produced in the liver, carried to the kidneys by the circulatory system. Marine reptiles drink seawater in order to obtain a supply of water but are unable to produce a concentrated urine that has a higher osmilarity than their body fluids. They make up for this by using specialized glands for the secretion of salts in a hyperosmotic fluid. The salt glands of these marine reptiles secrete a concentrated salt solution to enable them to drink saltwater even though their kidneys cannot produce urine more concentrated than seawater. (CC) ([|6])

(ORS 16)

<span style="color: #4f6228; font-family: Algerian; font-size: 18pt; line-height: 115%; margin: 0in 0in 10pt;">Circulation <span style="color: #4f6228; font-family: 'Times New Roman',serif; font-size: 14pt; line-height: 115%;">Reptiles have a circulatory scheme called double circulation. This allows flow of blood to organs and tissue. Unlike fish, reptiles have pulmonary and systemic circuits, which cause less mixing of oxygen-rich and oxygen-poor blood. Their three chamber heart has a partially divided ventricle that assists the systemic circuits. The three chamber heart has two atria and one ventricle.[The atria are responsible for receiving blood and the ventricle is responsible for pumping the blood so that it is able to circulate throughout the entire body of the reptile. (MP) [|8]]Even though most reptiles have three chambered hearts, the Crocodiles and alligators have the four chamber heart, where the ventricle is divided into two chambers. The three chambered heart provides a more <span style="color: #4f6228; font-family: 'Times New Roman',serif; font-size: 19px; line-height: 21px;">rigorous <span style="color: #4f6228; font-family: 'Times New Roman',serif;"> flow of blood to the body as compared to the two chambered fish heart because the three chambered heart pumps blood a second time after the blood loses pressure in the pulmonary circuit. However, it is still less efficient than the four chambered heart because some mixing of oxygen poor and oxygen rich blood does occur.(KL)(15)

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<span style="color: #4f6228; font-family: Algerian; font-size: 18pt; line-height: 115%; margin: 0in 0in 10pt;">Self Protection <span style="color: #4f6228; font-family: 'Times New Roman','serif'; font-size: 14pt; line-height: 115%; margin: 0in 0in 10pt;">Reptiles have multiple forms on self protection. For turtles their form of protection is the hard shell around the. Some snakes have venomous fangs that be used as a defense. Other reptiles use coloring, which helps camouflage them from predators. Crocodiles and alligators have extremely think scaled bodies that are hard to penetrate and keep well hidden just under the water surface. Many Reptiles have their skin of scales as protection. In one case the Australian frill neck lizard spreads its frill to scare away predators.

<span style="color: #4f6228; font-family: 'Times New Roman','serif'; font-size: 14pt; line-height: 115%; margin: 0in 0in 10pt;">Some types of lizards have a unique defense mechanism against predators- the ability to shed their tail at will. This ability, also known as caudal autonomy, is an amazing display of reptile morphology, as the lizards can grow back the tail, and is also an incredibly effective tool for survival. There are a number of benefits to it. The main benefit is distraction- the startling display of the tail removal, and the subsequent wriggling of the tail is often enough for the lizard to make a quick escape while the predator is occupied with the strange appendage. The next benefit is appeasement- the predator, if aware of the situation, is more likely to settle with the jettisoned tail than to keep chase of the lizard. The last benefit is venom overdose prevention. If chased by a venomous predator, the tail of the lizard is most likely spot for a venomous strike. As a result, the detachment of the tail means less of the chance any injected venom will reach vital organs. (TM)(1)

Sea turtles have an amazing defense mechanism as well. Unlike land turtles, they cannot simply hide in their shell when a shark is coming at them. Instead, They swim towards the shore, attracting the shark to shallow water. Once there, the shark cannot swim as quickly and the turtle actually goes on the offensive. It charges at the shark, using its strong bite. Usually they do not kill the shark, but since their goal is to get away, they force the shark to retreat and therefor succeed.(GR) [|19]



<span style="color: #4f6228; font-family: Algerian; font-size: 18pt; line-height: 115%; margin: 0in 0in 10pt;">Osmotic Balance <span style="color: #4f6228; font-family: 'Times New Roman','serif'; font-size: 14pt; line-height: 115%; margin: 0in 0in 10pt;">Reptiles use osmoregulation to maintain water balance within their system. The main role of osmoregulation is to manage the body’s water content and solute composition. The keratinized skin on reptiles is water proof, which helps prevent dehydration, especially in dry air.

<span style="color: #000000; font-family: Arial; font-size: 14pt; line-height: 115%; margin: 0in 0in 10pt;">Osmoregulators (inncluding invertebrates, fishes, amphibians, reptiles, and mammals) are generally hyperosmotic to their environment. The problems that they face because of this are that they are subject to swelling by movement of water into their bodies owing to the osmotic gradient. Therefore, they have continual loss of salts into the surrounding environment (which, compared to their bodies, have a low salt content). They way these animals deal with these problems is to produce a large volume of dilute urine. The kidney absorbs the salts that are needed, and the rest of the water is excreted. Another way these animals deal with lack of salt is by obtaining it from food. Also, they use active transport across their skin. (RG) [|(10)]

<span style="color: #4f6228; font-family: Algerian; font-size: 18pt; line-height: 115%; margin: 0in 0in 10pt;">Temperature Balance <span style="color: #4f6228; font-family: 'Times New Roman','serif'; font-size: 14pt; line-height: 115%; margin: 0in 0in 10pt;">Rather than using their metabolism for temperature balance, reptiles instead use behavioral adaptations to maintain this balance. Reptiles are ectotherms and not just cold-blooded creatures. This means they absorb external heat rather than generating it themselves. One way they may do this is if the air is cool they would use the sun to increase their internal body temperature. Also reptiles are able to survive on less than 10% of the calories required by a mammal the same size due to the fact reptiles use solar energy rather than through the metabolic breakdown of food.

1. Why is the reptile's ability to shed its tail advantageous? How does this characteristic enhance the survival of reptiles? (MT) 2. What are the differences between ectoderms, cold-blooded creatures, and warm blooded creatures? What are the advantages to each? 3. Describe the process of double circulation while comparing and contrasting the reptile circulatory system with that of a mammal, a fish and an amphibian (CSR). 4. What are the advantages for some reptiles to have a 4 chambered heart in comparison to the "typical" 3 chambered heart of a reptile? Consider the factors to why some reptiles may have adapted a 4 chambered heart. (CW) 5. What adaptations (including waste removal) do reptiles have that aid them in preserving water in arid environments? (ORS)
 * Review Questions**

<span style="color: #4f6228; font-family: Algerian; font-size: 18pt; line-height: 115%; margin: 0in 0in 10pt;">Sources <span style="color: #4f6228; font-family: 'Times New Roman','serif'; font-size: 14pt; line-height: 115%; margin: 0in 0in 10pt;">1. http://www.sciencedaily.com/releases/2009/03/090325170604.htm (TM) <span style="color: #4f6228; font-family: 'Times New Roman','serif'; font-size: 14pt; line-height: 115%; margin: 0in 0in 10pt;">2. http://animal.discovery.com/guides/reptiles/snakes/anatomy_03.html (YA) 3. http://www.ideacenter.org/contentmgr/showdetails.php/id/1113 (ZXU) 4) []﻿5. [] 6.http://www.cartage.org.lb/en/themes/sciences/zoology/animalphysiology/osmoregulation/osmoregulation.htm 7. [] (MC) 8. http://www.buzzle.com/articles/reptiles-characteristics-of-reptiles.html (MP) 9. [] (NG) 10. [] 11. http://www.heat-pits.com.au/images/male-snake-anatomy.png (anatomy of a snake) (MP) 12. [] (LW) 13. @http://www.trexmuseum.org/whatsrept.html (SM) 14. [] 15. <span style="font-family: 'Times New Roman',serif; font-size: 16px; line-height: 18px;">Campbell, N.C., Reece, J.R. (2002). //Biology.// (Sixth Edition). San Francisco: Benjamin Cummings. <span style="font-family: 'Times New Roman',serif; font-size: 16px; line-height: 18px;">16.[](ORS) <span style="font-family: 'Times New Roman',serif; font-size: 16px; line-height: 18px;">17. http://whiteafrican.com/wp-content/snake.jpg (ZS) <span style="font-family: 'Times New Roman',serif; font-size: 16px; line-height: 18px;">18. http://whiteafrican.com/wp-content/snake2.jpg (ZS) <span style="font-family: 'Times New Roman',serif; font-size: 16px; line-height: 18px;">19.http://www.hawaiianatolls.org/research/NOWRAMP2002/journals/babyhonu.php (GR) <span style="font-family: 'Times New Roman',serif; font-size: 16px; line-height: 18px;">20. http://www.youtube.com/watch?v=5CchyctRFrQ 21. [] (JS) 22. http://people.eku.edu/ritchisong/Turtle-Resp.jpg (RL) 23. [] (DB)