Difference Between Amphibians and Reptiles

Main Difference – Amphibians vs Reptiles

Amphibians and reptiles are two groups of animals. Both of them are cold-blooded animals with a backbone. Amphibians have soft skins with slippery secretions on it. Reptiles lay hard-shelled eggs. They undergo incomplete metamorphosis as their life cycle is composed of egg, larva, and adult stages. Their skin is covered with scales or bony external plates. The main difference between amphibians and reptiles is that amphibians live in aquatic environments during their larval stage and adults migrate to the land whereas reptiles are adapted to live in terrestrial environments. Caecilians, frogs, toads, salamanders, newts, and mudpuppies are examples of amphibians. Turtles, tortoises, lizards snakes, crocodiles, alligators, and tuatara are reptiles.  

Key Areas Covered

1. What are Amphibians
     – Definition, Facts, Characteristics
2. What are Reptiles
     – Definition, Facts, Characteristics
3. What are the Similarities Between Amphibians and Reptiles
     – Outline of Common Features
4. What is the Difference Between Amphibians and Reptiles
     – Comparison of Key Differences

Key Terms: Amphibians, Ectothermic, Eggs, Incomplete Metamorphosis, Larva, Limbs, Reptiles, Vertebrates

What are Amphibians 

Amphibians refer to the cold-blooded, vertebrate animals that possess an aquatic gill-breathing larval stage and terrestrial, lung-breathing adult stages. Most amphibians are ectothermic animals. Thus, they depend on external sources for regulating the body temperature. Their metabolic processes require a regulated body temperature. The skin of the amphibians is thin, soft, hairless, and porous. It contains both mucus and poison glands. The skin of a reed frog is shown in figure 1.

Figure 1: Skin of a Reed Frog

Ten pairs of cranial nerves start from the brain in amphibians. They have two eyes with colored vision. The vision is restricted to a narrow range of color spectrum. Amphibians have a large mouth with small teeth. But, some amphibians swallow their food as a whole. The neck consists of a single vertebra, limiting the articulation of the head. Some amphibians have four legs. Each limb consists of webbed feet and a varying number of digits. But, true nails and claws are absent. Some amphibians such as caecilian are limbless. Some amphibians such as tadpoles use their lateral line to sense water pressure changes, locating the prey. A limbless, South American caecilian is shown in figure 2.

Figure 2:  Siphonops paulensis

Amphibians are unisexual animals that exhibit external fertilization. The eggs are laid in moist environments. The larval stage is aquatic, and their respiration occurs through gills. The adult stage is morphologically different from the larva. It moves to the terrestrial environment and breath through lungs. Amphibians are the only vertebrates that undergo incomplete metamorphosis. A mass of amphibian eggs is shown in figure 3.

Figure 3: Frogspawn

Some amphibians such as Japanese giant salamander do not have any natural predators may live about 80 years. Aposematic coloration and nocturnal activity may protect amphibians from predation. Slippery skin and toxic substances also help to avoid predation.

What are Reptiles

Reptiles are the cold-blooded, vertebrate animals who possess a dry, scaly skin and lay shelled-eggs on the land. As reptiles are cold-blooded animals, they regulate their body temperature according to the environmental temperature. Reptiles have a watertight-skin due to the presence of a horny epidermis layer. Their skin is thinner than that of mammals and lacks a dermal layer. Some reptiles such as turtles have a hard shell. Others have soft or hard scales. The skin of a sand lizard is shown in figure 4.

Figure 4: Sand Lizard Skin

The vision of most reptiles is adapted to daylight. The visual depth perception of reptiles is more advanced than that of amphibians and mammals. Most reptiles are tetrapods. However, some reptiles such as snakes do not possess limbs. Their spinal column aids in locomotion. Reptiles have a large cerebrum and cerebellum. They have twelve cranial nerve pairs. A turtle is shown in figure 5.

Figure 5: Caretta caretta

Reptiles are also unisexual animals with internal fertilization. The eggs of them can be covered either with calcareous or leathery shells. The most used reproduction method is oviviparity. The tail of some reptiles can be shed as a defense mechanism. The principal defense mechanism of snakes is the delivery of venom to the enemy.

Similarities Between Amphibians and Reptiles

• Both amphibians and reptiles belong to the phylum chordate under the kingdom Animalia.
• Both amphibians and reptiles are ectothermic (cold-blooded) animals.
• Some amphibians and reptiles have four limbs.
• Both amphibians and reptiles have a heart with three chambers.
• Many amphibians and reptiles are capable of altering the color of the skin by concentrating or dissipating melanin.
• Both amphibians and reptiles are mostly omnivores.
• Many amphibians and reptiles have a sharp eyesight, aiding the capturing of the prey by flicking their tongues.
• Both amphibians and reptiles use biting, inflating, and camouflage to avoid predation.
• Both amphibians and reptiles have the same opening that serves as the genital, intestinal, and urinary outlet called cloaca.
• Both amphibians and reptiles rely on spinal segmental reflexes for locomotion.

Difference Between Amphibians and Reptiles

Definition

Amphibians: Amphibians are cold-blooded, vertebrate animals who possess an aquatic gill-breathing larval stage and terrestrial, lung-breathing adult stages.

Reptiles: Reptiles are cold-blooded, vertebrate animals who possess a dry, scaly skin and lay shelled-eggs on the land.

Origin

Amphibians: Amphibians were first evolved about 370 million years ago.

Reptiles: Reptiles were first evolved about 315 million years ago.

Significance

Amphibians: Amphibians are animals with dual modes of existence.

Reptiles: Reptiles are creeping or crawling animals.

Classification

Amphibians: Amphibians belong to class Amphibian.

Reptiles: Reptiles belong to class Reptilia.

Number of Species

Amphibians: Around 5,500 species of amphibians can be identified worldwide.

Reptiles: Around 6,500 species of reptiles can be identified worldwide.

Habitat

Amphibians: Amphibians live partly in both water and shady land.

Reptiles: Reptiles are adapted to live in terrestrial environments.

Skin Covering

Amphibians: Amphibians have soft skins protected by a slippery secretion of mucus.

Reptiles: Reptiles have a skin with hard or soft scales.

Method of Breathing

Amphibians: Amphibians use gills or lungs to breathe.

Reptiles: Reptiles use lungs to breathe.

Fertilization

Amphibians: Amphibians undergo internal fertilization.

Reptiles: Reptiles undergo external fertilization.

Mode of Reproduction

Amphibians: Oviviparity is the mode of reproduction in amphibians.

Reptiles: Oviparity is the mode of reproduction in reptiles.

Eggs

Amphibians: The eggs of amphibians are covered with a transparent gelatinous covering.

Reptiles: Reptiles have amniotic eggs, which are hard or leathery.

Birth

Amphibians: Amphibians are born in water or mushy lands with gills and tails.

Reptiles: Reptiles are born on the land.

Physical Appearance of the Young

Amphibians: The physical appearance of the young may differ from the adult.

Reptiles: The physical appearance of the young is similar to the adult.

Limb

Amphibians: Amphibians have four short limbs.

Reptiles: Some reptiles have four limbs. But, the others lack limbs.

Cranial Nerves

Amphibians: Amphibians have ten pairs of cranial nerves.

Reptiles: Reptiles have twelve pairs of cranial nerves.

Excretion

Amphibians: The main nitrogenous waste of amphibians is ammonia.

Reptiles: The main nitrogenous wastes of reptiles is uric acid.

Defense

Amphibians: Amphibians defend through toxic secretions through the skin and bite.

Reptiles: Reptiles defend with claws, whipping tails, venomous, and bites.

Conclusion

Amphibians and reptiles are two types of chordates. Both are cold-blooded animals that possess differences in their skins as an adaptation to their habitat. Amphibians live in both water and land. But, reptiles live in terrestrial habitats. The main difference between amphibians and reptiles is the habitat of each type of animals.

Reference:

1.  Prakash, Mohini. Characteristics of Class Amphibian, Available here.
2. “Reptiles Facts.” Animals Information, Available here.

Image Courtesy:

1. “Tree frog congo” By Nhobgood Nick Hobgood – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Siphonops paulensis02” By Ariovaldo Giaretta – (CC BY-SA 2.5) via Commons Wikimedia
3. “Frogspawn closeup” By Tarquin at the English language Wikipedia (CC BY-SA 3.0) via Commons Wikimedia
4. “Lacertae skin” By User:Gruzd – Self-photographed (CC BY-SA 3.0) via Commons Wikimedia
5. “Caretta caretta 060417w2” By Strobilomyces – Own work (CC BY-SA 3.0) via Commons Wikimedia