What Makes Reptilia Unique? Traits, Types & Common Questions
Class Reptilia, animals of which class are called Reptiles, are some of the important vertebrates on the planet Earth, and hence it is important for the students of biology to learn about them. If we think carefully, the creatures from the class Reptilia, are a few of those creatures many of whom can live on the land and under the water. And also, a few of the members from the class Reptilia can be found in the common household as well, such as lizards.
Therefore, it is necessary for the students of biology to learn about the class Reptilia, not only from the perspective of the exam but also from the perspective of biological curiosity. But there is also one more important thing, and that is students need to have an explanation that is easy to comprehend and understand, otherwise you may not be able to understand the topic of Reptilia, its characteristics and types.
Hence, Vedantu provides to the students of Biology the complete Explanation of Reptilia along with its Characteristics, Classification. And it is prepared by the expert educators in such a manner that it becomes extremely easy for the students to understand it, and hence to grasp the same topic as well.
An Overview of the Class Reptilia.
The animals of the class Reptilia are commonly called reptiles. An interesting thing about reptiles is that many scientists and researchers believe that they were the first ones to adopt life on the earth. Scientists also believe that the ancestors of the reptiles were amphibians, and about millions of years ago, the Reptiles evolved from there.
Turtles, Crocodilians, and Squamates, that is to say, lizards and snakes, are the three major groups of Class Reptilia. There are a total of 8000 known species of these groups collectively. Out of these 8000 species, 9 percent of species are associated with inland water, which consists of turtles, crocodilians, snakes, and lizards. A diverse suite of physiological as well as morphological adaptations has been developed by those species of reptiles which associated themselves with the freshwater habitats.
General Characteristics of Reptilia.
There are many characteristics of Reptilia, some of which are discussed below:
Most of the Reptilia possess a continuous external epidermal covering of scale, which is a small plate or shield that forms a part of the outer layer of the skin in some animals, and it provides them with protection against the environment.
Keratin is the type of protein, and one type of such Keratin which is called Beta keratin is present in the scales of the Reptilia, while there is another type of unique keratin which is called Alpha Keratin, and it is present in the interscalar skin of the Reptilia.
The body of the Reptilians is divided into four parts, which are head, neck, trunk, and tail.
Their skins do not have any glands and it is dry and rough.
The respiration systems of the Reptilia work with the help of the lungs.
Except for the Crocodiles, which have 4 chambered hearts, all the other Reptilia have 3 chambered hearts.
FAQs on Reptilia: Characteristics and Classification
1. What are the defining characteristics of animals in Class Reptilia?
Animals in Class Reptilia are vertebrates that exhibit several key characteristics adapted for terrestrial life. The most important features include:
Body Covering: Their skin is dry and covered with epidermal scales or scutes, which prevent water loss.
Respiration: They breathe exclusively through lungs throughout their life.
Thermoregulation: They are poikilothermic (cold-blooded), meaning they rely on external sources to regulate their body temperature.
Heart Structure: Most reptiles have a three-chambered heart with a partially divided ventricle. Crocodiles are an exception with a four-chambered heart.
Reproduction: Fertilisation is internal, and they are mostly oviparous, laying amniotic eggs with a protective leathery shell. This allows them to reproduce on land.
Limbs: When present, they have two pairs of pentadactyl (five-toed) limbs.
2. How are living reptiles classified? Provide examples for each major order.
The living members of Class Reptilia are classified into four major orders based on their anatomical and physiological features:
Order Testudines (or Chelonia): This group includes turtles, tortoises, and terrapins. Their most distinct feature is a protective bony or cartilaginous shell developed from their ribs. Examples: Indian Star Tortoise, Green Sea Turtle.
Order Squamata: This is the largest order, comprising lizards and snakes. They are characterised by their movable quadrate bones, which allow them to open their mouths very wide. Examples: King Cobra, Chameleon, Wall Lizard.
Order Crocodilia: This order includes large, semi-aquatic predators like crocodiles, alligators, caimans, and gharials. They are known for having a fully four-chambered heart. Examples: Saltwater Crocodile, Gharial.
Order Sphenodontia (or Rhynchocephalia): This ancient order contains only one living genus, the tuatara, found in New Zealand. They are often called 'living fossils'. Example: Tuatara.
3. Why are reptiles considered the first truly successful terrestrial vertebrates?
Reptiles are considered the first truly successful terrestrial vertebrates because they evolved three key adaptations that freed them from dependency on water, unlike amphibians:
The Amniotic Egg: This was the most critical innovation. The egg's shell and internal membranes (amnion, chorion, allantois) prevent the embryo from drying out, provide nourishment, and manage waste, allowing reptiles to lay eggs on land.
Scaly Skin: Their dry, cornified skin covered in scales creates a waterproof barrier. This drastically reduces water loss from the body, enabling them to thrive in dry environments where amphibians would perish.
Advanced Respiration: Reptiles have more developed lungs and associated rib cage muscles for efficient breathing, which is far superior to the skin and simple lung respiration seen in amphibians.
4. How does the circulatory system of a crocodile differ from that of a lizard?
The primary difference lies in the structure of the heart. A lizard, like most reptiles, has a three-chambered heart, consisting of two atria and one partially divided ventricle. This partial division allows for some mixing of oxygenated and deoxygenated blood. In contrast, a crocodile has a more advanced four-chambered heart, with two atria and two completely separate ventricles. This complete separation prevents the mixing of oxygenated and deoxygenated blood, allowing for more efficient oxygen transport, which is similar to the circulatory system of birds and mammals.
5. What is the evolutionary significance of having scales instead of moist skin like amphibians?
The evolution of scales was a pivotal adaptation for a terrestrial lifestyle. Unlike the moist, permeable skin of amphibians which is used for cutaneous respiration and requires a damp environment, reptilian scales offer two major advantages:
Prevention of Desiccation: The primary function of scales is to create a waterproof barrier that significantly reduces water loss from the body. This allowed reptiles to colonise a wide range of dry, terrestrial habitats far from water sources.
Physical Protection: The tough, keratinised scales provide a durable layer of armour against predators, parasites, and physical abrasions in their environment. This is a significant improvement over the delicate skin of amphibians.
This shift meant that reptiles were no longer tied to aquatic or moist environments for survival, marking a major step in vertebrate evolution.
6. Are all reptiles 'cold-blooded'? Explain the correct scientific term and its implication.
While commonly called 'cold-blooded,' the more accurate scientific term for reptiles is poikilothermic or ectothermic. This means they cannot generate and maintain a constant internal body temperature. Instead, their body temperature varies with the surrounding environment. The implication of being ectothermic is that reptiles must rely on behavioural thermoregulation. For instance, they bask in the sun to warm up and become active, and they seek shade or burrows to cool down. This dependence on external heat sources is why reptile activity is often limited in cold climates or during colder parts of the day.
7. What are some examples of venomous and non-venomous snakes found in India?
Snakes, belonging to the order Squamata, show a wide diversity in India. It is important to distinguish between venomous and non-venomous species.
Examples of Venomous Snakes: India is home to the 'Big Four' highly venomous snakes responsible for most snakebite incidents. These are the Indian Cobra (Naja naja), Common Krait (Bungarus caeruleus), Russell's Viper (Daboia russelii), and the Saw-scaled Viper (Echis carinatus).
Examples of Non-Venomous Snakes: The vast majority of snakes are non-venomous and harmless to humans. Common examples include the Indian Rock Python, Rat Snake, and the Common Sand Boa.
