Metamorphosis

Facts: History and Science Facts

Facts: History and Science Facts
Our editors will review what you've submitted, and if it meets our criteria, we'll add it to the article. Their excretory system consists of two small kidneys. Such structures bring blood into close association with the external medium so that the exchange of gases takes place across relatively small distances. Exposure to radiation can also result in cancers of the bone marrow leading to leukemia , lungs, kidneys, bladder, esophagus, stomach, colon, thyroid, or breasts. An Outline of Entomology.

The gases in the environment

Respiratory system

In the next phase, the part of the diaphragm that surrounds the esophagus relaxes, thus helping to open the esophagus. The longitudinal muscle of the esophagus contracts, further opening the junction between the stomach and esophagus. The pressure forces the contents of the stomach up into the esophagus and out of the mouth for reviews with much more detail, see Brizzee , Lang and Sarna , Miller Rats are considered a non-vomiting species also called nonemetic Hatcher Rats do not vomit in response to cues that cause vomiting in other animals, like emetic drugs, poison, motion-sickness, and radiation e.

Rats also don't belch and experience hardly any reflux heartburn. Rats cannot vomit, but they do regurgitate occasionally. Regurgitation is different from vomiting. Vomiting is the forceful expulsion of stomach contents from the mouth. Vomiting is an active process: In contrast, regurgitation is the passive, effortless flow of undigested stomach contents back into the esophagus.

Regurgitation happens without any forceful abdominal contractions. There is at least one report of rats choking on regurgitated stomach contents Will et al. Upon necropsy, the regurgitated stomach contents regurgitant were found to be thick and pasty. They were packed into the rats' pharynx, larynx and esophagus.

The action of the tongue had packed the regurgitant into a plug, causing choking. The rats' tongues were also lacerated or bruised from attempts to remove the material by chewing or clawing.

Regurgitation was more common in rats fed bulky diets than those fed on standard diets, and more common in females than in males. Rats may have trouble swallowing a food item. A rat who has trouble swallowing a food item may strain intently, pull his chin down toward his throat and flatten his ears.

He may drool saliva, paw at his mouth, and rub his mouth on nearby surfaces. Most rats are still able to breathe through this true choking is rare in rats , and work the food out themselves in time, but serious cases may require veterinary asssitance. Difficulty swallowing may superficially resemble vomiting because partly processed food may come back out of the mouth, but it is not vomiting, which is the forceful, rapid, coordinated, reflexive explusion of stomach contents.

This foam is not made of stomach contents, but of mucus brought up from the lungs that has been whipped up into a froth. This foam is a symptom of a respiratory problem, not regurgitation or vomiting pers comm B. Diagram of the rat's stomach. Adapted from Moore Diagram of a rat stomach opened along the greater curvature of the stomach.

Adapted from Robert Diagram of the crural sling and the muscle bundles of the esophageal sphincter, which make up the gastroesophageal barrier and are responsible for closing the esophagus. Adapted from Montedonico et al. The rat's esophagus has two layers of striated muscle outer longitudinal and inner circular , which become smooth near the attachment point with the stomach. The esophagus is closed off from the stomach by the gastroesophageal barrier , which consists of the crural sling , the lower esophageal sphincter , and the several centimeters of intraabdominal esophagus that lie between them Soto et al.

Humans also have a crural sling and an esophageal sphincter, but ours are placed right on top of one another Mittal In rats, they are separated by several centimeters of intraabdominal esophagus Soto et al. The crural sling is part of the diaphragm its outer contour is continuous with the diaphragm.

It is a U-shaped bundle of fibers that wraps around the esophagus and attaches to the vertebrae. When the crural sling contracts it pinches the esophagus closed. The esophageal sphincter is a circular muscle that surrounds the base of the esophagus. At its lower edge, it has muscle fibers that insert into the limiting ridge Fig 4. So when the sphincter contracts, it not only constricts the walls of the esophagus, it also pulls the sides of the limiting ridge's "U" together, thus hiding and tightly closing the esophageal opening Montedonico et al.

Insects which undergo holometabolism pass through a larval stage, then enter an inactive state called pupa called a "chrysalis " in butterfly species , and finally emerge as adults. The earliest insect forms showed direct development ametabolism , and the evolution of metamorphosis in insects is thought to have fuelled their dramatic radiation 1,2. Some early ametabolous "true insects" are still present today, such as bristletails and silverfish.

Hemimetabolous insects include cockroaches, grasshoppers, dragonflies, and true bugs. Phylogenetically, all insects in the Pterygota undergo a marked change in form, texture and physical appearance from immature stage to adult.

These insects either have hemimetabolous development, and undergo an incomplete or partial metamorphosis, or holometabolous development, which undergo a complete metamorphosis, including a pupal or resting stage between the larval and adult forms. A number of hypotheses have been proposed to explain the evolution of holometaboly from hemimetaboly, mostly centering on whether or not the intermediate hemimetabolous forms are homologous to pupal form of holometabolous forms.

More recently, [ when? According to research from , adult Manduca sexta is able to retain behavior learned as a caterpillar. Many observations [ when?

In typical amphibian development, eggs are laid in water and larvae are adapted to an aquatic lifestyle. Frogs , toads , and newts all hatch from the eggs as larvae with external gills but it will take some time for the amphibians to interact outside with pulmonary respiration.

Afterwards, newt larvae start a predatory lifestyle, while tadpoles mostly scrape food off surfaces with their horny tooth ridges. Metamorphosis in amphibians is regulated by thyroxin concentration in the blood, which stimulates metamorphosis, and prolactin , which counteracts its effect. Specific events are dependent on threshold values for different tissues.

Because most embryonic development is outside the parental body, development is subject to many adaptations due to specific ecological circumstances. For this reason tadpoles can have horny ridges for teeth, whiskers, and fins.

They also make use of the lateral line organ. After metamorphosis, these organs become redundant and will be resorbed by controlled cell death, called apoptosis. The amount of adaptation to specific ecological circumstances is remarkable, with many discoveries still being made. With frogs and toads, the external gills of the newly hatched tadpole are covered with a gill sac after a few days, and lungs are quickly formed.

Front legs are formed under the gill sac, and hindlegs are visible a few days later. Following that there is usually a longer stage during which the tadpole lives off a vegetarian diet. Rapid changes in the body can then be observed as the lifestyle of the frog changes completely. The animal develops a big jaw, and its gills disappear along with its gill sac.

Eyes and legs grow quickly, a tongue is formed, and all this is accompanied by associated changes in the neural networks development of stereoscopic vision, loss of the lateral line system, etc. All this can happen in about a day, so it is truly a metamorphosis. It is not until a few days later that the tail is reabsorbed, due to the higher thyroxin concentrations required for tail resorption.

The Salamander development is highly diverse; some species go through a dramatic reorganization when transitioning from aquatic larvae to terrestrial adults, while others, such as the Axolotl , display paedomorphosis and never develop into terrestrial adults. But, the females of some species are known to protect their eggs and hatchlings. For example, female Pythons coil themselves around the eggs in order to protect them and regulate their temperature.

Similarly, crocodiles are known to guard their young after the eggs hatch. TDSD or temperature-dependent sex determination can be observed in many Reptiles.

In TDSD, the incubation temperature determines the sex of the offspring. This characteristic is most commonly seen in crocodiles and turtles, but can also occur in tuataras and lizards. Different food habits can be observed between the four sub-groups.

Animals belonging to the Crocodilia, Squamata and Sphenodontia sub-groups are carnivores, feeding on a wide range of prey from vertebrates to fish and insects. The Testudines are herbivorous in nature with their diet comprising of fruits, shrubs, leaves, grass and marine plant materials like kelp and algae. The populations of many Reptilian species are facing rapid decline due to various factors like deforestation, loss of habitat, hunting for hide and to use them for edible purposes.

Various Reptile populations have faced extinction in some specific locations. Due to these reasons, many species are protected by law in most of the countries where they are found. Many Reptile species, including various lizards and turtles, are very popular all over the world as exotic pets.

There is a widespread popularity even for the venomous snakes, especially among keen animal lovers. However, there is a common misconception that these animals do not need as much care as required by mammal pets. The truth is that, Reptiles need to be taken care of properly; otherwise, they cannot survive in captivity.

They should be kept in large tanks or cages where they can move freely. It is not advisable to keep more than one to two animals in a single enclosure. Their tanks should have suitable substrate and the animals should be provided with special heating lamps to allow them to bask and maintain their body temperature.

The temperature of the tanks needs to be monitored with the help of thermostats. Heating pads can also be used for this purpose. Custom made cages can also be used for this purpose as these mimic the natural habitat of a specific species in the best manner possible. It is advisable to place stones, pieces of wood and small plants in their tanks to provide them with basking spots.

Using a fogger to mist the enclosure may be advisable for certain species. When keeping snakes or poisonous lizards as pets, one should keep in mind not to handle them with bare hands. One should do extensive research and read appropriate books regarding how to best take care of them before petting any Reptilian animal. These pets can survive as much as mammalian pets of similar size when properly taken care of. The Ringneck Snake is a species of small North American snakes that belong to the harmless colubrid family.

The Banded Water Snake also called the southern water snake is a species of aquatic snake widely distributed in parts of the United States. The Water Monitor is a species of giant monitor lizard found in parts of South and Southeast Asian countries. These semi-aquatic reptiles are common t. The African Fat-tailed Gecko is a species of lizard abundantly spread throughout the western regions of the continent of Africa.

Often confused with i. Black caimans found in South America are the fourth largest extant member of the crocodile family. These robust reptiles were almost hunted to extinct. Dwarf caimans found in South America are the smallest crocodilian belonging to the alligator family. It is one of the two members in its genus, the ot. The Emerald Tree Boa is a non-venomous boa species that is considered to be one of the most beautiful snakes in the world. They are known for their cr.

Common leopard geckos, also known as the spotted fat-tailed gecko, are terrestrial lizards found in Asia. Reproduction in whole or in part without permission is prohibited. Reptile Classification According to the taxonomy, they belong to the kingdom Animalia, phylum Chordata and the clade Amniota. The Reptilia class is further divided into several extant sub-groups: There are around species in this sub-group, including turtles, tortoises and terrapins. This subgroup includes the two living tuatara species from New Zealand.

This is the biggest sub-group of the Reptilia class, having over 9, species including lizards, worm lizards and snakes. This subgroup consists of 25 different species including crocodiles, alligators, caimans and gavials.

Reptile Defense Mechanism The useful defenses of these animals help them to survive in their wild habitat. Camouflage Birds and larger Reptiles are among the main predators of many smaller lizards and snakes. Tail Shedding and Regenerating Various lizards like skinks and geckos can shed their tail when captured by it. Defense in Snakes The principal defense mechanism in various snake species is their ability to deliver poison through their fangs.

Evolution of Reptiles These animals originated around million to million years ago with the first reptiles evolving from the advanced reptiliomorph labyrinthodonts. Reptile Anatomy Eyes Most Reptiles are unable to see properly during nighttime as their vision is mainly adapted to the daylight conditions.

Skin The horny epidermis layer makes their skin watertight, allowing these animals to inhabit dry land. Respiratory System Reptiles use their lungs for breathing. Digestive System Majority of these animals have short digestive tracts because their diet mainly consists of meat, which is very simple to digest. Nervous System The basic nervous system in the Reptiles is similar to that in the Amphibians.

Skeletal System Most of these animals are tetrapods, meaning they have four legs. Excretory System Their excretory system consists of two small kidneys. Characteristics of Reptiles Reptiles have certain characteristic features that help in distinguishing them from Amphibians, Mammals and Aves: Unlike Amphibians who have gills during their juvenile stage, Reptiles breathe through lungs at all stages of their lives.

Apart from crocodiles, all Reptiles have three-chambered hearts.

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