Sunday, February 28, 2021

Amphibians Classification

What is Amphibians Classification?

Amphibians classification is defined as cold-blooded small vertebrate animals that can adapt in both land and water ecosystem. 

These animals are born in water and grow to become adults through a process called metamorphosis. They are typically living on terrestrial habitat but move to aquatic habitat for breeding. 

The amphibians live a double life as a connecting link between land and water ecosystems. For example- Frogs, toads.

The baby frog is known as a tadpole with no legs and lungs. At this stage, the tadpoles are quite similar to fishes.

They have gills to breathe in water and tail to swim like fishes. However, once they grow into adults, their tail vanishes. Now, they are grown up and spend time both in water and land as per their wish and requirements.

Amphibian is an essential class of animal kingdom that can survive in water as well as on land. Many species come under amphibians.

Let us have an overview of the general characteristics of these animals before we start with amphibian’s lower classification. 

General Characteristics of Amphibians

These are the general characteristics of amphibians. The classification of amphibians depends on these characteristics. However, some characteristics may vary from one species to another. 

  • Amphibians are inhabitants of both terrestrial and sea habitat.
  • These are cold-blooded animal species.
  • Their body can divide into two parts- head and trunk. Some species may have a tail as well.
  • Two pairs of limbs help them in locomotion. 
  • Their skin has no scales.
  • Their skin has mucous glands that help to keep them moist.
  • The external ear is not present in amphibians.
  • They use gills in the larval stage and lungs in the adult stage for respiration.
  • Their heart has three chambers.
  • The RBCs of amphibian species are biconvex and nucleated.
  • They have a bony endoskeleton.
  • The alimentary canal, excretory & urogenital tract of amphibians opens outside through cloaca.
  • Amphibian species are generally oviparous that lay eggs.
  • The development of these species consists of larval stages. 

Amphibians Classification

There are approximately 6200 amphibian species that live on the planet. All the species play an essential role in the environment. As far as the classification of amphibians is concerned, they can classify into different subclasses and orders. The amphibian’s lower classification is as follows. 

Kingdom- Animalia

Phylum- Chordata

Subphylum- Vertebrata

Superclass- Tetrapoda

Class- Amphibia

Class Amphibia

It refers to a double lifestyle. This class includes animals like salamanders, frogs, toads, and caecilians that cover almost 3900 species of amphibia class.

These species are tetrapod, that means the animals have four limbs. These limbs evolve from pectoral and pelvic fins that facilitate them moving about on land. 

The skin of amphibian class species is moist, glandular, and magid (except caecilians). The skin of caecilians has scales as fishes have.

They have unique characteristics that allow them to survive in both ecosystems (land and water) and also play an essential role in the food chain.

We start the classification of amphibians with a subclass Stegocephali.

  • Subclass Stegocephali

The term Stegocephali is used for four-limbed stem-tetrapod animals and in phylogenetic nomenclature of all the tetrapod species. They are extinct animal species with pentadactyle limbs. Their skin covered with scale and bony plates. 

The subclass Stegocephali can divide into three orders- Labyrinthodontia, Phyllospodyli, and Lepospodyli. The general characteristics of the animals that belong to these orders are as follows. 

  • Order Labyrinthodontia

  •  These are primitive animals that belong to the classification of animals.
  • “Stem Amphibia” is another synonym of these species.
  • They characterize by big teeth having folded dentine as crossopterygian ancestors (fishes) used to have. 
  • For example- Eryops (extinct).
  • Order Phyllospodyli

  • These animals look like a small salamander.
  • The spinal cord and notochord of these amphibians open in a joint cavity. 
  • For example- Branchchiosaurs (extinct). 
  • Order Lepospondyli

  • These animals have similarities with small eels. 
  • They are vertebrae of a single piece.
  • They have a neural arch and centrum continuous.
  • For example- Diplocaulus (extinct). 
  • Subclass Lissiamphibia

They are a group of tetrapod animals that includes all the amphibians of the modern era. Subclass Lissiamphibia consists of three orders- Apoda, Urodela, and Anura.

The general characteristics of these orders are given below for a better understanding of the classification of amphibians.

  • Order Gymnophiona or Apoda

  • These are worm-like animals with no legs.
  • They are subterranean diggers by nature.
  • Their eyes may be covered by skin or even sometimes covered by bones.
  • They have tentacles on their head. They use their tentacles as a chemosensory organ to find out the underground prey.
  • The initial growth of the fetus of these species gets support from the yolk sack. The embryo feed on uterine milk that secretes from the epithelial wall of the oviduct. 
  • Order Caudata or Urodela

  • They are lizards like animals of amphibians lower classification with a tail. 
  • They generally have two pairs of limbs, usually of equal size.
  • Their skin is smooth without scales and glandular with mucus & poison glands. They use these glands to get protection against predators.
  • These animals generally live under leaf litter, in soil, or maybe wholly aquatic.
  • These animal species mostly have internal fertilization through spermatophore. Almost 90% of species that belong to Caudata utilizes spermatophores for internal fertilization. 
  • The larval development to adult occurs through some stages of metamorphosis.
  • They all are predaceous as they feed on insects, worms.
  • The species of Order Urodela are subdivided into five suborders- Cryptobranchiodea, Ambystomatoidea, Salamandriodea, Proteidea, and Meantes. 
  • For example- Ambystoma, Siren.
  • Order Salientia or Anura 

  • In the adult stage, these animals do not have a tail.
  • They have eyelids and tympanum.
  • Their skin is without scales and quite loose.
  • These animals have four limbs with unequal sizes. Their hind limbs can extend and modified for jumping.
  • Their head and trunk are fused. The tail is present in the larval stage, but it disappears as it grows adult.
  • They follow external fertilization where eggs and sperms are shed on the water surface directly.
  • The animals of Order Anura is subdividing into five suborders- Amphicoela, Optisthocoela, Anomcoela, Procoela, and Diplasiocela.
  • For example- Frog, Toad.

The animals that belong to amphibians lower classification are equally crucial to nature as other groups of animals.

They play a vital role both as prey and a predator too. They feed various insects that minimize the threat of various diseases, but unfortunately, around 40% of amphibian species are at risk.

There are various causes such as pollution, loss of habitat. That are responsible for these species to become threatened.

Hence, we need to do necessary preventive measures to protect these species for the betterment of the environment. 

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