21.+chordata-+reptilia

Chordata - Reptilia //** Varanus komodoensis **//

1. Classification/Diagnostic characteristics:

 * The Varanus komodoensis is better known by its c ommon name, Komodo dragon.
 * They have a tough skin covered with scales or modifications of scales such as hair and feathers.
 * The largest of the species reach 165 kilograms and can grow up to three meters in length.
 * Male Komodo dragons are typically larger than females, but there are no obvious differences in appearance.
 * Strong limb, muscular tail, round snouts and ear openings in the head are distinctive traits of the Komodo dragon. (1)



2. Relationship to humans:

 * Komodo Dragons are the dominant predators on the islands they inhabit. (13)
 * Large enough Komodo dragons are able to consume whole humans.
 * It has a deadly bite that contains over 50 strains of bacteria and will kill an organism it bites within 24 hours.
 * Komodo Dragons are thought to have evolved in Australia long before humans arrived at the island (approximately 3000 years before). (10)

3. Habitat and niche:

 * Adult Komodo dragons live mainly in tropical savannah forests and prefer open lowland areas with tall grasses and bushes.
 * They are also found in beaches, ridge tops, and dry river beds. (1)

4. Predator avoidance:

 * Komodo dragons have deadly bacteria in their saliva that kills any organism that it bites. (7)
 * It also has razor sharp claws to keep predators away and defend itself.
 * Adult Komodo dragons do not have any natural predators, they are at the top of the food chain.

5. Nutrient acquisition:
The Komodo Dragon identifies its food through its sense of smell, as its eyesight and hearing are significantly less refined than its sense of smell. Komodo Dragons, when attacking an animal, go for the feet first. Furthermore, if an animal escapes, since its bite is deadly, the animal will die soon after. The Komodo Dragon will also eat almost any type of meat. Although specific research has not been completed, the recent discovery of venom may imply that venoms may be used in order to subdue prey. Additionally, due to its septic bite, an injury caused by its bite will rapidly lead to infection. (2)



6. Reproduction and life cycle:

 * The embryo will grow inside mother in an amniote egg, an egg relatively impermeable to water and allows the embryo to develop in a contained aqueous environment.
 * It reproduces by laying eggs.
 * Male Komodo dragons will engage in ritual combat to mate with females. They wrestle to try to throw the loser to the ground, often drawing blood. (1)
 * When females are ready to mate, they give off a scent in their feces that males can detect. Males then locate the female, rub their chin on her head, scratch her back, and lick her body. If the female shows interest, she licks him back and then they mate. (1)

7. Growth and development:

 * After Komodo dragons hatch from eggs, they live in trees to avoid being eaten by adult Komodo dragons. They stay above the ground eating eggs, insects, birds, and small mammals for eight months - at eight months old, they are too heavy to be supported by branches and come down to live on the ground. Then, they start to change their diet to larger prey. (1)
 * A young Komodo dragon is significantly smaller than an average adult.
 * Their lifespan is about 50 years. (13)

8. Integument:

 * The Komodo dragon's skin is reinforced by strong scales. These many scales contain osteoderms, tiny bones that function as almost a natural "chain-mail".
 * Their skin is coated with waxy keratin which protects it from the environment. (5)
 * Because of the scales, they have a very rugged hide which makes for poor leather.

9. Movement:

 * It is a four-legged organism, and walks around 3 mph but can run up to 13 mph over short distances.
 * The Komodo dragon's distinctive walk is characterized by the head, body, and tail swaying side to side.
 * They are very strong swimmers, which benefits them when stalking prey.
 * In their early year, Komodo dragons are good climbers. As weight and age increase, they lose their ability. (5)

10. Sensing the environment:
The Komodo dragon relies on a very well developed olfactory sense to locate its food and can detect the smell of decomposing flesh as far away as 11 kilometers. The Komodo dragon actually gathers scent molecules via its tongue which is passed on to the sense organs and brain. The Komodo dragon has limited sight and diminished hearing capacity. (6)

11. Gas exchange:

 * The Komodo dragon utilizes a pair of lungs to exchange oxygen and carbon dioxide between the tissues and air.
 * It cannot use its skin as a method of gas exchange.
 * Its lungs also are inflated and deflated by the expanded and contracted rib cage. Fresh air flows into the reptile's lungs, and stale air flows out. (4)

12. Waste removal:
The digestive and excretory systems of the Komodo dragon compares to the mammalian sets to a point. While they exhibit mouths, esophagi, stomach, and intestines, the dragon has one region, called the cloaca, for the expulsion of both urine and feces. Also, in contrast, uric acid replaces urea as the main excretion product in the species to conserve water, which is necessary due to the animal's less developed kidneys (no renal pelvis, no loop of Henle, and fewer nephrons). (8)(9) However, the dragon does possess more efficient digestive behavior and physiology--while mammals like the tiger excrete about a third of ingested mass, the dragon excretes 3 times less at around 10%, meaning they also do not need to eat or defecate often. (3) (11)

13. Environmental physiology (temperature, water, and salt regulation):

 * Adaptions have freed reptiles from a close association with water:
 * They are amniotes and don't need water to reproduce, they use internal fertilization and lay eggs with shells
 * A tough, dry, and impermeable skin, covered with scales or modifications of scales such as hair and feathers, greatly reduces water loss
 * Excrete nitrogenous wastes as uric acid semisolids, using little water in the process (12)

14. Internal Circulation:

 * The Komodo Dragons heart has three different chambers; the left atrium, right atrium, and ventricle.
 * The first step of circulation:
 * Oxygen-poor blood goes from the right atrium to the ventricle in the heart, to the lungs through the pulmonary vein.
 * Then oxygenated blood from the lungs of the Komodo dragon is moved back to the left atrium of the heart through a pulmonary artery.
 * The second step of circulation:
 * Oxygenated blood is carried from the left atrium to ventricle of the heart and then distributed throughout the body.
 * Then deoxygenated blood is carried back to the right atrium for the process to start over.
 * The ventricle is able to pump both oxygenated and deoxygenated blood throughout the Kamodo Dragon because of the numerous folds in the ventricle. (12)

15. Chemical Control:

 * Have fairly complex endocrine systems similar to those of humans
 * They contain adrenal glands and many more similarities. (2) (5)

//**1) If Komodo dragons do not have a digestive tract similar to that of humans, how do they expel solid waste from their bodies?**//
It has one region, called the cloaca, for the expulsion of both urine and feces. Also, uric acid replaces urea as the main excretion product in the species to conserve water.

//**2) In what ways are reptile circulatory systems similar to those of amphibians? of mammals?**//
Reptiles have a three-chambered heart, like amphibians. They can't use their skin for gas exchange, like mammals.

//**3) Are there any morphological (physical structure) differences between male and female Komodo dragons?**//
No, but male Komodo dragon's tend to be larger than their female counterparts. Also, females tend to have a more red coloring on their flanks or noses.

//**4) How does the Komodo dragon search, detect, and kill its food?**//
The Komodo Dragon identifies its food through its sense of smell, as its eyesight and hearing are significantly less refined than its sense of smell. When attacking an animal they go for the lower body first, because if an animal escapes, since its bite is deadly, the animal will die soon after.

**5) What is the average lifespan of the Komodo dragon? What are the stages of its life?**
The average lifespan of a Komodo dragon is about 50 years, and it goes through the stages of an embryo, child, then adult. Children have difficulty making it into adulthood, lots fall victim to predators including some from their own species.


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=** Sources: **=

http://animaldiversity.org/accounts/Varanus_komodoensis/ (1) https://nationalzoo.si.edu/animals/komodo-dragon (2) https://www.britannica.com/animal/reptile/Digestive-and-urogenital-systems (3) http://www.austincc.edu/sziser/Biol%201413/LectureNotes/lnexamIV/Phylum%20Chordata-Reptiles.pdf (5) http://www.draconian.com/dragons/komodo-dragon-hunting.php (8) http://www.zooborns.com/zooborns/2009/12/the-mighty-komodo-dragon-at-its-smallest.html (9) https://en.wikivet.net/Lizard_and_Snake_Excretion (11) http://library.sandiegozoo.org/factsheets/komodo_dragon/komodo.htm (6) http://www.kapunahala.k12.hi.us/student_projects/komodo/predators.htm (7) https://www.nationalgeographic.com/animals/reptiles/k/komodo-dragon/ (13) https://www.livescience.com/9726-origin-komodo-dragon-revealed.html (10) http://www.biology-pages.info/V/VertebrateLungs.html (4) http://tolweb.org/treehouses/?treehouse_id=4457 (12)

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