Class Amphibia

Class Amphibia is a subclass of the animal kingdom that includes all amphibians, which are animals that are capable of surviving both on land and in water. These are vertebrates that are typically not very large in comparison to their surroundings. Amphibian is derived from the Greek term ‘amphibious,’ which literally means ‘living on two feet.’ This illustrates the fact that amphibians can survive in both aquatic and terrestrial environments, which is significant. However, it is possible to find animals that live entirely on land or entirely in water within the group of amphibians that are classified as terrestrial.

Amphibians are a critical link in the chain of life that began in the oceans and has spread throughout the world. Approximately 8000 different species of amphibians have been identified to date. Their ancestors lived during the Middle Mississippian Epoch, when their species first appeared on the scene. Scientists believe that what we now know as amphibians were in fact the first animals to make the transition from the sea to the land, despite the fact that this has not been proven conclusively.

Amphibians can be found almost everywhere on the planet, with the exception of the Antarctic region. Additionally, they can be found in arctic regions, as well as in arid environments. They are extremely beneficial in the production of crops because most varieties of amphibians attack and feed on insects that cause crop damage, making them extremely beneficial.

Classification of Amphibian

Living Members of Amphibians are Grouped Under three Orders

Order 1. Gymnophiona

Blind and limbless, elongated and worm-like in appearance

The tail is either too short or completely absent.

The limb-girdle is not present.

Caecilians, as an illustration.

Order 2.  Urodela, it is Divided into Five Suborders

Cryptobranchoidea

Adult without an eyelid who is the most primitive and permanently aquatic creature on the planet.

It is possible to fertilise from the outside.

As an illustration, Cryptobranchus

Ambystomatidae

Having a home on the land

Adult with a drooping eyelid

Fertilisation on an internal level

As an illustration, Ambystoma

Salamandridae

Opisthocoelous Vertebrates are found in the area.

Roof palate internal fertilisation is accomplished through the use of teeth.

As an illustration, the Salamander

Provider

Having a life as aquatic creatures

Without eyelids and lungs, there is nothing to see.

Proteus is a good example of a cartilaginous skull.

Meanies

Aquatic larvae without eyelids, representing permanent larvae

Meantes, for example, has horny jaws.

Order 3. 

Anura

Amphibian without a tail Adult without gills Amphibian without a tail

Bufo sativus as an example of internal fertilisation

Scientific Classification

Kingdom – Animalia

Phylum – Chordata

Clade- Batrachomorpha

Class- Amphibia

Characteristics of Class Amphibia

General Characters 

Amphibians are animals that can live both on land and in water, and they are classified as such.

Amphibians are the first vertebrates to make the transition from an aquatic to a terrestrial mode of life. Amphibians are the first vertebrates to make the transition from an aquatic to a terrestrial mode of life.

Habit and habitat

Amphibians can be found in both freshwater and moist water environments.There are no marine forms to be found.Some frogs prefer to live in trees. As an illustration, Hyla (tree frog).

Temperature It is (poikilothermic), and the majority of forms hibernate during the colder months.During the dry summer months, some of them become active.

Body Form

There are many different shapes and sizes of their bodies, ranging from broad to narrow, long to short and cylindrical.It is divided into four sections, which are as follows: the head, the neck, the trunk, and the tail.

Some amphibians do not have a neck, while others do.

Appendages

Two pairs of pentadactyl limbs, each with four to five pure digits, are present in the creature.Some amphibians do not have any limbs at all (Apoda).

For leaping, frogs and toads have hindlimbs that are larger than the four limbs that they have.

These are approximately the same size as those found in salamanders and newts.

Digits are devoid of claws, nails, or hooves, and they are frequently covered in webs.

Skin

It is smooth and moist, and it is densely packed with multicellular mucus. It also contains poisonous glands.

In most species, it has a high level of vascularity and is respiratory.

The majority of the scales are absent ( except Apoda).

Endoskeleton The majority of it is made of bone.

The skull is flat and cacodylic, which means it has two occipital condyles, as shown in the illustration.The notochord does not remain in place.The first vertebra is specialised in that it is responsible for some of the movement of the head.

Digestive System 

The mouth is large and armed with teeth in either the upper or lower jaws, depending on the species.

Teeth are acrodont, which means they are curved.

Amphibians (frogs and toads) are the first vertebrates to have a true tongue, which they acquired during their evolution.

In frogs and toads, a true tongue is a soft mucus-coated structure that is attached at the front end.

The alimentary canal is a tube that connects the stomach to the cloaca.

Respiratory System 

Lungs are responsible for respiration (Pulmonary respiration)

Skin of the buccopharyngeal cavity (Cutaneous respiration) Gills of the buccopharyngeal cavity (Branchial respiration)

Circulatory System

The heart has three chambers, two of which are called auricles and one of which is called ventricle.

This is an improvement over the previous 2-chambered fish heart design.

The left and right auricles receive blood from the lungs and the rest of the body, respectively, while the middle auricle does not. The ventricle is responsible for pumping out mixed blood.

There are two sinuses present: the sinus venosus and the truncus arteriosus.The renal portal system has advanced to a high level of development.RBC cells are biconvex and oval in shape, and they contain nuclei.

Cranial Nerves and Sense Organs

There are ten pairs of cranial nerves in the human body.

There is no external ear to speak of.

In addition to the internal ear, the middle ear contains a single auditory ossicle, which is responsible for hearing.

The middle ear is protected by the tympanum.

Lateral line sense organs are found in larvae and aquatic forms of life, among other things.

Reproductive System

Gonoducts lead to the creation of colada.Sexual dimorphism is distinct from the differences between the sexes.Males are devoid of a copulatory organ.

Fertilisation and Development

Fertilisation is primarily done externally (It is internal in salamander).

They are oviparous, meaning they produce eggs.

A larval stage in the aquatic environment is common (tadpole).

Amphibians are descended from lobe-finned, bony fishes that breathed through their lungs.

Their paired fins were pierced by a fleshy lobe that developed into limbs.

In the present day, the Latimeria species serves as a living fossil representation of this ancestral species.

Conclusion

The Chordata phylum of the kingdom Animalia is home to the organisms that belong to the class Amphibia, which is composed of amphibians. The term refers to multicellular vertebrates that can be found on both land and in water. There are approximately 3000 species in this class. They were the first cold-blooded animals to appear on the surface of the planet.