Essential Characteristics: Reptiles and Amphibians Compared
The following article discusses the subtle differences between reptiles and amphibians. In general, they are grouped in biological classifications because their cold-blooded structure gives them common characteristics and evolutionary history. However, crocodiles and alligators are not included in this article because they are considered by many to be more closely related to birds than amphibians or reptiles. Students should keep in mind that all reptiles and amphibians also share some common features such as dry skin (instead of hair), scales (or feathers), lungs (instead of a diaphragm), and laying eggs (excluding live birth).
What are Reptiles?
The term reptile originated from Latin "repere". It meant "to crawl", which is a defining aspect of reptiles. Those are members of Class Reptilia which are cold-blooded animals. Moreover, it has four orders –
Crocodilia
Example – Crocodile, alligator
Squamata
Example – lizard, snake
Testudines
Example – Turtle, tortoise
Sphenodontia
Example – Tuataras
Characteristics of Reptiles
The main characteristics are –
Prefers to live in warm habitats
Presence of nasal slits and Jacobson's organ (except in crocodile and turtle)
Body covered by scales
Note that the main difference between mammals and reptiles can be seen in body covering. The presence of body hair is a defining characteristic of mammals, whereas reptiles have a keratin epidermal layer called scales. Consequently, mammals have sweat glands that are not present in reptiles.
What are Amphibians?
Amphibians are members of Class Amphibia, which live both on land and water. Furthermore, it primarily comprises three orders –
Anura
Example – Frog
Urodela
Example – Salamander
Apoda
Example – Caecilians
Characteristics of Amphibians
The main characteristics are –
Amphibians cannot regulate body temperature
Existence of larval stage that starts after eggs are hatched
They can live both inland and in water. Hence, amphibians can breathe both through gills and lungs.
Fun Facts!
While reproduction of any living being is a natural course, in the case of reptiles, it is dependent on temperature to a large extent. In addition, most of the reptiles lay eggs except pythons and boas, which give birth to young ones.
Moreover, it is the soil temperature that determines whether the new hatchling will be male or female!
Difference Between Amphibians and Reptiles
It is considered that reptiles primarily originated from amphibians, environmental factors led to the evolution of the former species. Thereby, the unique features apparent in amphibians and reptiles' differences helped to ensure the survival of these species.
Similarities Between Amphibians and Reptiles
Even though there are differences between amphibians and reptiles in points, owing to amphibians previously zoologically classified as reptiles leads to similarities shared by the species. Both belong to the phylum Chordata and subphylum Vertebrata.
Body metabolism is ectothermic. That is, body temperature changes corresponding to extraneous factors
Omnivorous eating habit
Presence of the cloaca as the common outlet for intestinal, urinary and genital functions
Reflex spinal segments help in locomotion
Test Your Knowledge
i. Reptile Eggs are Also -
(a) Waterless
(b) Amniotic
(c) Prehistoric
(d) Gigantor
ii. Tail-Less Amphibian Found Under Which Order?
(a) Order Anura
(b) Order Caudata
(c) Order Gymnophiona
(d) Both under order Gymnophiona and order Caudata
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Conclusion
Reptiles and amphibians are two different types of animals belonging to the kingdom Animalia. The main difference between amphibians and reptiles can be seen in their physiological adaptations, body covering, mode of reproduction, egg structure and presence/absence of limbs. Reptiles are cold-blooded animals whose skin is covered by scales, whereas amphibians are those whose skin lacks scales and is poisonous. Amphibians metamorphosis as they grow, whereas reptiles do not undergo such a process. Reptiles lay eggs, whereas amphibians give birth to live young ones. Furthermore, it is the soil temperature that determines whether baby reptiles will be male or female!
Hope you all liked this article on the difference between amphibians and reptiles. Keep learning, and stay tuned to Vedantu!
FAQs on Reptiles vs Amphibians: What Sets Them Apart?
1. What are the five main differences between amphibians and reptiles?
The five primary differences between amphibians and reptiles relate to their skin, reproduction, life cycle, respiration, and heart structure.
- Skin: Amphibians have smooth, moist, and glandular skin that is permeable, while reptiles have dry, scaly skin that is waterproof.
- Reproduction: Most amphibians exhibit external fertilisation in water, whereas reptiles reproduce through internal fertilisation.
- Eggs: Amphibians lay soft, shell-less (anamniotic) eggs in water. Reptiles lay hard or leathery-shelled amniotic eggs on land.
- Life Cycle: Amphibians undergo metamorphosis (e.g., tadpole to frog), while reptiles hatch as miniature versions of adults.
- Respiration: Adult amphibians can breathe through lungs, skin, and the lining of their mouth. Reptiles breathe exclusively through their more developed lungs.
2. How are Class Amphibia and Class Reptilia distinguished in biological classification?
In formal biological classification as per the CBSE/NCERT syllabus, Class Amphibia and Class Reptilia are distinguished by key anatomical and physiological traits. Amphibians (e.g., frogs, salamanders) are defined by their dual life (aquatic larval stage, terrestrial adult), ectothermic nature, and a three-chambered heart. In contrast, Class Reptilia (e.g., lizards, snakes, crocodiles) includes vertebrates that possess epidermal scales, breathe solely with lungs, and have a three-chambered heart with an incomplete ventricle septum (or a four-chambered heart in crocodiles). The most critical distinction is that reptiles produce an amniotic egg, a major evolutionary adaptation for terrestrial life that amphibians lack.
3. What is the fundamental difference in the skin of a reptile versus an amphibian?
The fundamental difference lies in structure and function, which dictates their habitats. An amphibian's skin is smooth, moist, and permeable, containing many glands. This type of skin allows for cutaneous respiration (breathing through the skin) but also makes them prone to dehydration, tying them to water or damp environments. A reptile's skin is dry, tough, and covered in keratinous scales. This waterproof barrier is crucial for preventing water loss, enabling reptiles to thrive in a wide range of dry, terrestrial habitats.
4. How does reproduction in reptiles differ from that in amphibians?
Reptiles and amphibians have fundamentally different reproductive strategies. Most amphibians practice external fertilisation, where the female lays eggs in the water and the male fertilises them outside her body. In contrast, all reptiles practice internal fertilisation, where the male transfers sperm into the female's cloaca. This difference is directly linked to their eggs; the shell-less amphibian egg requires an aquatic environment, while the shelled reptilian egg is adapted for development on land.
5. What are some important similarities between reptiles and amphibians?
Despite their many differences, reptiles and amphibians share several key characteristics. Both are vertebrates, meaning they possess a backbone. Both groups are also ectothermic (cold-blooded), relying on external environmental sources to regulate their body temperature. Furthermore, most species in both classes have a cloaca, which is a single posterior opening that serves for the excretion of urinary and faecal waste as well as for reproduction.
6. Why is a crocodile classified as a reptile and not an amphibian, even though it lives in water?
A crocodile's aquatic lifestyle is a behavioural adaptation, but its classification is based on its biological traits. A crocodile is a reptile because it possesses all the key reptilian features:
- It has tough, scaly skin, not the permeable skin of an amphibian.
- It breathes air exclusively with lungs, even when in water.
- It reproduces via internal fertilisation and lays hard-shelled, amniotic eggs on land.
- It does not undergo a larval stage with metamorphosis like a frog's tadpole stage.
These features firmly place it in Class Reptilia, regardless of its semi-aquatic habitat.
7. Do reptiles undergo metamorphosis like amphibians do?
No, reptiles do not undergo metamorphosis. Amphibians are known for their distinct two-part life cycle, which includes an aquatic larval stage (like a tadpole) that is structurally different from the adult. This larva undergoes a dramatic transformation, or metamorphosis, to become an adult. Reptiles, on the other hand, exhibit direct development. They hatch or are born as smaller, sexually immature versions of the adult and grow to maturity without a fundamental change in their body plan.
8. Why are amphibians so dependent on water while reptiles can live in dry deserts?
This difference in habitat tolerance is due to two critical evolutionary adaptations in reptiles that amphibians lack. Firstly, amphibians have permeable skin that loses water easily and must be kept moist for survival and respiration. Secondly, they lay shell-less eggs that would dry out and perish if not laid in water or a very damp location. Reptiles overcame these limitations with a waterproof, scaly skin that prevents dehydration and the development of the self-contained amniotic egg, which provides a protective, moist environment for the embryo to develop in on dry land.
