Difference Between Amphibians and Reptiles

Edited by Diffzy | Updated on: October 17, 2023

       

Difference Between Amphibians and Reptiles

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Introduction

Reptiles and amphibians may have many similar characteristics like being close to the ground, often living in water. etc. But they have considerable differences in terms of the three Bs: Body, Breeding, and Behavior. Let’s start with how they are similar before anything else: Reptiles and amphibians are vertebrates or backboned animals. Although most animals have four legs, both groupings have several outliners.

Amphibians Vs. Reptiles

This takes us to the key distinction that will enable us to determine whether the long, legless animal you observe is a snake or a caecilian: SKIN. The skin of reptiles is dry and covered with scales. The skin of amphibians is a little moist with mucus so that it doesn't dry out. They do not have any scales on their skin. The eggs of reptiles have a hard or leathery shell while that of amphibians are transparent and jelly-like.

Difference Between Amphibians and Reptiles in Tabular Form

ParametersAmphibiansReptiles
DefinitionAmphibian means “living double lives” on water and land.Reptile means “creeping stealthily under cover of darkness.”
SkinSmooth, moist, and sometimes sticky, with mucous glands.Scale, dry
BreathingGills and lungs.Lungs.
ReproductionLay soft eggs, usually in water or damp places.Lay hard, leathery eggs on land, or they keep their eggs inside their bodies until they hatch.
MetamorphosisYes, breathing water through gills until developing lungs.No.
DefenseSecrete toxic poisons; can also bite; do not have claws.Use claws, tail-whipping, and biting.

What is an Amphibian?

Amphibians are ectothermic, four-limbed vertebrates that belong to the class Amphibia. The phylum Lissamphibia includes every extant amphibian. They live in a wide range of habitats, with the majority of species being found in freshwater aquatic, terrestrial, fossorial, or arboreal settings. Therefore, amphibians normally begin their lives as aquatic larvae, but some species have evolved behavioral adaptations to get around this.

The young typically transition from a larval stage with gills to an adult form with lungs. Some small terrestrial salamanders and frogs rely solely on their skin for respiration, while amphibians use their skin as a supplementary respiratory surface. Although they resemble lizards on the surface, reptiles, like mammals and birds, are amniotes and do not need bodies of water to procreate. Amphibians are frequently used as ecological indicators because of their intricate reproductive requirements and porous skins, yet there has been a sharp fall in amphibian populations for numerous species all over the world in recent years. The first amphibians originated from sarcopterygian fish in the Devonian period, which had lungs and bone fins that helped them adapt to dry land. During the Carboniferous and Permian periods, they evolved and rose to dominance, but subsequently, reptiles and other vertebrates supplanted them. There has been a debate for a long time over the ancestry of current frogs that are members of the Lissamphibia order, which first appeared during the Early Triassic, some 250 million years ago. They most likely descended from temnospondyls, the most varied group of prehistoric amphibians, during the Permian epoch, according to the developing consensus.

Frogs, salamanders, and caecilians make up three current orders of amphibians, which are classified as Anura, Urodela, and Apoda. The Albanerpetontidae, a fourth group, vanished approximately 8,000 species of amphibians are known, with frogs making up almost 90% of them. A New Guinean frog named Paedophryne amanuensis, which measures just 7.7 mm (0.30 in) in length, is the tiniest amphibian (and vertebrate) in the entire animal kingdom. The Mastodonsaurus, a prehistoric temnospondyl, which could grow to a length of 6 meters (20 feet), is dwarfed by the 1.8 m (5 ft. 11 in.) South China’s giant salamander (Andrias Sligo), is the largest amphibian alive today. Herpetology, which includes the study of both reptiles and amphibians, is the study of herpetology, while batrachology is the study of amphibians.

Due to paedomorphosis, which is brought on by two evolutionary trends- miniaturization and an exceptionally big genome that result in a slower growth and development rate than other vertebrates, modern amphibians have a simplified anatomy compared to their ancestors. Their quick metamorphosis, which appears to have evolved only in the ancestors of Lissamphibia; in all other known lines, the growth was considerably more gradual, is another factor contributing to their size. The metamorphosis occurs early on when the larvae are still little because remodeling of the feeding mechanism prevents them from eating during the process. As a result, the metamorphosis must quickly the smaller the individual. (Salamanders of the larger species don’t undergo a metamorphosis). In many cases, the entire transformation occurs inside the egg of an amphibian that lays eggs on land. Due to diffusion issues, anamniotic terrestrial eggs have a diameter of less than 1 cm, a size that restricts the amount of post-hatching expansion.

Since they have cold blood, amphibians are ectothermic vertebrates, which means they do not regulate their body temperature internally. Because of their low metabolic rates, they have modest dietary and energy needs. They have movable eyelids and tear ducts in the adult stage, and the majority of species have ears that can pick up vibrations from the ground or the air. They have strong tongues that can protrude in some species. The vertebra of modern amphibians has fully ossified and articular processes. They frequently have short ribs that may be fused to the vertebrae. Their skulls are typically small and wide, and frequently only partially ossified. Except for a few scales that resemble fish on some caecilians, its skin has negligible keratin content and is scale-free.

Numerous mucous glands as well as poison glands, a form of granular gland, are found in the skin of several animals. Amphibians’ hearts have two atria and one ventricle, for a total of three chambers. They have a urinary bladder, and urea is the main way that nitrogenous waste is expelled. The majority of amphibians lay their eggs in water, producing aquatic larvae that eventually change into terrestrial adults. Amphibians use a pumping mechanism to breathe, first drawing air into their buccopharynx through their nostrils. These are then shut, and by contracting the throat, the air is propelled into the lungs. They add skin-to-skin gas exchange as a supplement.

What is a Reptile?

According to the most frequent definition, reptiles are any animal that belongs to the class Reptilia, which includes all sauropsids other than birds. Turtles, crocodilians, squamates (lizards and snakes), and rhynchocephalians (tuatara) are all examples of living reptiles. The Reptile Database has over 12,000 species as of May 2023. There have been several inconsistencies in taxonomic definitions of the reptilia. Birds are regarded as belonging to a different class than reptiles in the conventional Linnaean categorization scheme. The name “Reptilia” has been redefined as a clade in modern cladistics classification systems, which include birds inside the group since crocodilians are more closely related to birds than they are to other extant reptiles. Other cladistics definitions do away entirely with the term “reptile” in favor of the term “amniote,” which is used to describe all amniotes that are more closely related to contemporary reptiles than to mammals. Herpetology is the study of traditional reptile orders, typically in conjunction with the study of contemporary amphibians.

 Tetrapod vertebrates, such as snakes, have four limbs, and reptiles are descendants of organisms with four limbs. Reptiles don’t have an aquatic larval stage like amphibians do. The majority of reptiles are oviparous, while some squamate species and some extinct aquatic clades are viviparous. This means that the fetus grows inside the mother utilizing a (non-mammalian) placenta rather than being enclosed in an eggshell. Since reptiles are amniotes, their eggs are encased in membranes for both transportation and protection, which allows them to reproduce on dry land. Many viviparous species feed their fetuses through different placental structures like those in mammals, and some of these species even care for their hatching at first. The smallest known reptile, the Sphaerodactylus ariasae gecko, can reach a length of only 17 mm (0.7 in.), while the largest, the saltwater crocodile Crocodylus porosus, can grow to a length of overb6 m (19.7 ft) and weigh over 1,000 Kg.

Early in the twenty-first century, vertebrate paleontologists started to embrace phylogenetic taxonomy, in which all groups are classified in a way that makes them all monophyletic, or groups that contain all offspring of a specific ancestor. Since they don’t include either birds or mammals, the reptiles according to historical definitions are paraphyletic. Both of these, which were once referred to as “reptiles”, descended from early therapsids and dinosaurs, respectively.

The first reptiles developed from sophisticated reptile morphs some 310-320 million years ago in the steamy swamps of the late Carboniferous period, giving rise to the reptiles as we know them today. Casineria is the first known animal that might have been an amniote (but it might have been a temnospondyl). The classic reptilian toes and scale imprints can be seen in a set of footprints from the Nova Scotian fossil layers that date to 315 Ma.

The Main Difference Between Amphibians and Reptiles in Points

  • In contrast to amphibians, which fertilize their eggs after laying them in water, reptiles typically lay their eggs on dry land and have internal fertilization.
  • While amphibians are born with gills for breathing underwater where they hatch and spend their early growth (developing lungs and legs later), reptiles are born with lungs.
  • Reptiles often have sensitive skin that is thin and often coated in tough, protective scales. Similar to human hair and fingernails, these scales are also formed of keratin. In contrast, the skin of amphibians is either smooth and slimy or rough and dry. Frogs, salamanders, and caecilians all have slimy, smooth skin are larvae.
  • There are three main groups (orders) of amphibians: caecilians (the worm-like gymnophiones), anurans (frogs and toads), and urodeles (newts and salamanders). On the other hand, Currently, there are four different orders of reptiles. Animals like crocodiles and alligators are referred to as crocodilia.
  • Frogs, toads, salamanders, newts, and caecilians are some examples of amphibians. On the other hand, Terrapins, tuataras, lizards, snakes, crocodiles, and alligators are examples of reptiles.
  • While some adult amphibians have lungs, the majority of them breathe through their skin. A newborn tadpole that lives in water breathes through its gills. On the other hand, Reptiles cannot breathe via their skin; pulmonary respiration is their main method of breathing.
  • A three-chambered organ with two auricles and a ventricle, the heart is found in amphibians. With two auricles and a ventricle that is artificially separated, the reptile heart has three chambers. The only reptiles that have four chambers in their hearts are crocodiles.

Conclusion

Although reptiles and amphibians are distantly related, despite certain similarities, they can be identified by their physical characteristics and various life stages. Amphibians have “double lives” that alternate between living in the water with gills and on land as they become older and develop lungs. They are vertebrates with ectothermic bodies. The earliest animals to leave the sea and travel on land were early amphibians, which served as a key link between fish and terrestrial reptiles. Reptiles are a class of creatures that have scales or scale-like modifications, breathe air, and typically lay eggs. Their name means “to creep stealthily under cover of darkness.” The majority of reptiles are land animals that deposit eggs to reproduce. Reptiles include creatures like crocodiles, snakes, lizards, and turtles.

References

  • https://thebiologynotes.com/amphibians-vs-reptiles/
  • https://www.sheddaquarium.org/stories/amphibian-or-reptile-here-s-the-difference#:~:text=Reptiles%20have%20scales%2C%20and%20their,keeps%20them%20from%20drying%20up.

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