Understanding the Key Differences Between Amphibians and Reptiles

Think back to your elementary school days and your first science classes. Do you remember learning about the differences between amphibians and reptiles? If so, do you remember what separates these two classes of animals? You likely remember that they are both cold-blooded vertebrates. Maybe you remember that most reptile and amphibian species lay eggs rather than give birth to live young. Extra points if you recollect that they tend to shed their skin all at once through a process called molting or sloughing. However, do you remember all the critical differences that separate amphibians from reptiles?If not, don’t worry, we’ve got you covered. Continue reading to discover ten key differences that separate amphibians and reptiles.  

Comparing Amphibians and Reptiles

The 10 Key Differences Between Amphibians and Reptiles

Amphibians and Reptiles: Taxonomy

Despite their many similarities, amphibians and reptiles belong to different classes in the animal kingdom. Amphibians belong to the clade Batrachomorpha, which comprises all recent and extinct amphibians that share more in common with modern amphibians than with reptiles. They belong to the class Amphibia, which includes animals such as frogs, toads, salamanders, and caecilians. Meanwhile, reptiles belong to the clade Sauropsida, which consists of all amniotes that share more in common with modern reptiles than mammals. They fall under the class Reptilia, which contains animals like snakes, lizards, turtles, ad crocodiles. 

Amphibians and Reptiles: Habitat

While amphibians and reptiles range throughout the world and live in similar environments, they spend most of their time in different habitats. For example, most amphibians experience an aquatic stage as part of their life cycle. Many will spend the majority of their time in or near water, while some species spend their entire lives within the water. One example is the olm, a species of salamander that lives in caves. Olms rarely leave the water and may spend years underwater without ever breaching the surface. On the other hand, most reptiles spend the majority of their lives on land. Most do not have an aquatic stage of their life cycle, and although some will spend time in the water, few live out their lives in or near water. For example, while crocodiles spend a large portion of their time in the water, they still nest and rest on land. 

Amphibians and Reptiles: Skin

When comparing the skin of amphibians and reptiles, several differences become immediately apparent. Amphibians grow permeable skin, which allows them to breathe on land and in the water. Many species grow warts on their skin that have specific functions. Mucous glands generate mucus, which help to moisten an amphibian’s skin and keep it from drying out. Meanwhile, granular glands often produce a noxious, poisonous compound. This substance is usually extremely bad-tasting and sometimes toxic, which helps protect the animal from predators. Meanwhile, reptiles grow a hard, watertight epidermis. Some reptiles,  like turtles, grow dermal scales, while others, such as snakes, grow epidermal scales. Unlike amphibians, reptiles cannot secrete mucus through their skin, but many can still generate and deliver toxins through their fangs. 

Amphibians and Reptiles: Nervous System

Although they function similarly, there exists a difference in the complexity of the nervous systems in amphibians and reptiles. On average, the brains and nervous systems of amphibians are less well-developed than those found in reptiles. Amphibians tend to have a smaller cerebrum and cerebellum, which affect motor function, thought, and speech. All amphibians possess only 10 pairs of cranial nerves. These nerves relay information from the brain to different parts of the body, including sensory information like visual images, smells, and sounds. Compared to amphibians, the brains of reptiles are more complex. Reptiles have a larger, well-developed cerebrum and cerebellum. Like other higher vertebrates, they possess 12 cranial nerves. 

Amphibians and Reptiles: Respiration

The respiratory systems of amphibians and reptiles can vary dramatically. Compared to other amniotes, the lungs of amphibians are more primitive. To inflate their lungs, amphibians must utilize buccal pumping, which involves the animal moving the floor of its mouth to circulate oxygen throughout the body. In addition, most amphibians can also exchange gas through their skin, either in the air or in the water.  Reptiles cannot breathe through their skin. All reptiles breathe using their lungs, although some reptiles such as turtles evolved more permeable skin that allows for limited gas exchange through their cloaca. That said, most reptiles rely on their diaphragm or supporting muscular system to ventilate their lungs. 

Amphibians and Reptiles: Excretions

As a wise man once said, everyone poops and amphibians and reptiles are no different. However, there is a distinct difference in the composition of the secretions emitted by amphibians and reptiles. The primary byproduct in the waste of amphibians is ammonia. Since most amphibians aren’t concerned with conserving water, their bodies process large amounts of the substance and excrete the waste through their diluted urine. Meanwhile, as reptiles spend most of their time on land, they must conserve as much water as possible. As a result, the primary byproduct in their nitrogenous waste is uric acid.

Amphibians and Reptiles: Tongue

Another common difference between amphibians and reptiles is the shape of their tongues. Most amphibians have long, usually sticky tongues to help them pick up prey. This contrasts with the tongues of many reptiles, which are shorter and bifurcated. Their split tongue operates as a sensory organ that allows the animal to smell and detect prey. Bifurcated tongues exist commonly in many species of snakes and lizards. however, some reptiles possess long, sticky tongues to catch prey. Chameleons secrete a sticky, viscous mucus on their tongues that is 400 times thicker than human saliva. This sticky substance allows them to catch prey.

Amphibians and Reptiles: Eyes

The eyes of amphibians and reptiles evolved for specific reasons, which explains why they operate differently. Amphibians evolved to live both on land and in the water. As a result, their eyes can function equally well above and below water. However, their eyes can only see a limited range of colors. Evidence suggests that they can see certain hues in low light, whereas most eyes would only see black, white, or gray. Meanwhile, the eyes of most reptiles tend to be more well-developed. Since they only adapted to live on land, their eyes can view a broader range of colors, although they operate less well in water. In general, nocturnal reptiles evolve vertical pupils, while diurnal reptiles tend to sport round pupils. 

Amphibians and Reptiles: Eggs

While most amphibians and reptiles lay eggs, their eggs are wildly different from one another. Amphibian eggs appear gelatinous and contain various mucous compounds. The outer layer is permeable to water and gas and can absorb large amounts of water. To fertilize their eggs, amphibians may rely on internal or external fertilization. Once the eggs are fertilized, amphibians typically lay their eggs in water. On the other hand, reptiles lay amniotic eggs covered by a leathery or calcareous shell. Unlike amphibians, all reptile eggs require internal fertilization. However, some amphibians and reptiles give birth to live young, such as fire salamanders and garter snakes. 

Amphibians and Reptiles: Larva

The final difference between reptiles and amphibians concerns the larval stage. The life cycle of most amphibians usually begins with an aquatic larval stage. During this stage, young animals develop the systems and features they’ll need to survive as adults. Larvae undergo a process known as metamorphosis, during which their appearance changes from their larval form to their adult form. Unlike amphibians, reptiles do not go through a larval stage and subsequently do not undergo metamorphosis.  Instead, they either lay eggs or give birth to live young that emerge as fully formed juveniles that look like miniature adults.