Differences Between Reptiles And Amphibians

Kingdom  Animalia consists of about 11 important phyla. Each phylum has unique characteristics that define its organisms under it. The list of important phyla is as follows-

• Porifera 
• Coelenterata
• Ctenophora
• Platyhelminthes
• Nemathelminthes
• Annelida
• Arthropoda
• Mollusca
• Echinodermata
• Hemichordata
• Chordata

Basis of classification

Kingdom Animalia is classified based on-

1. Level of organisation

• Cellular level: In sponges, cells are arranged as loose cell aggregates, and division of labour occurs among the cells. So, tissues are absent.
• Tissue level: In coelenterates and ctenophores, cells performing the same function are arranged in tissues.
• Organ level: in Platyhelminthes, tissues are organised to form organs.
• Organ system level: In higher animals, organs further organise to form organ systems.

1. Symmetry 

• Asymmetry: When any plane that passes through the centre does not divide the body of the animals into two halves. For example, Sponges.
• Radial symmetry: Any plane passing through the body’s central axis will divide the animal into two identical halves. For instance, Coelenterates, Ctenophores, and Echinodermata.
• Bilateral symmetry: The body can be divided into identical left and right halves passing through only one plane. For example, Platyhelminthes to chordates.

1. Germinal layer

• Diploblastic: animals where the cells are arranged to form two embryonic germ layers- ectoderm and endoderm. An undifferentiated mass of cells is present between the endoderm and ectoderm, known as mesoglea. For example, Coelenterates and Ctenophores.
• Triploblastic: Those animals in which the developing embryo has three germ layers- ectoderm, mesoderm, and endoderm. For example, Platyhelminthes to Chordates.

1. Body cavity or Coelom: The presence or absence of a cavity between the body wall and the gut wall is known as a coelom. It is a very important basis for classification.

• Acoelomates: Animals in which the body cavity is absent. For example, Porifera, Coelenterata, Ctenophora, and Platyhelminthes.
• Pseudocoelomates: Mesoderm does not line the body cavity in all species. Instead, mesoderm is found in scattered pouches between the ectoderm and mesoderm. For example, Aschelminthes.
• Coelomates: Animals possessing body cavities or coelom lined by mesoderm. Coelomates are of two types- Schizocoelomates and Enterocoelomates. 

Schizocoelomates have coelom form by splitting of mesoderm. For example, Annelida, Arthropoda, and Mollusca.

Enterocoel has coelom formed by the fusion of gut pouches during the embryonic stage. For example, Echinodermata, Hemichordata, and Chordata.

1. Body plan

• Cell aggregate type of body plan is found in Sponges.
• Blind sac body plan: Animals in which a single opening is present, and it serves as both mouth and anus. For example, Coelenterates to Platyhelminthes. 
• Tube-within-tube type: Those animals have a separate opening for the mouth and anus. It is a complete digestive system. For example, Nemathelminthes to chordates.

1. Segmentation

• Pseudometamerism or false metamerism is found in Tapeworms.
• Metameric or true segmentation is found in Annelida, Arthropoda, and Chordates. In metameric animals, the body is segmented both inside and outwardly, with the repetition of organs. This is known as metamerism.

1. Notochord: A rod-like structure mesodermally derived and formed on the dorsal side at the embryonic development time. Based on this, animals are classified as chordates and non-chordates. Animals without notochords are non-chordates; those with notochords are known as chordates.

1. Circulatory system

• Open type: In this, blood is pumped out of the heart, and the cells and tissues are directly bathed. For example, Arthropods, Molluscs, Echinoderms, and Hemichordates.
• Closed type: In this type, blood flows in blood vessels such as arteries, veins, and capillaries. For example, Annelida, Vertebrates, etc.

1. Embryonic development: Based on the fate of blastopore, animals are divided into Protostomes and Deuterostomes.

Animals in which the mouth develops first are known as protostomes. For example, Platyhelminthes to Mollusca.

Animals in which the anus is formed first, and the mouth develops later are known as deuterostomes. For example, echinoderms, hemichordates, and chordates.

Class Amphibia 

• The Carboniferous period is the golden age of Amphibians.
• It includes animals that can live on both land and water. 
• They are the first chordates to come on land but cannot live permanently on land. They require water for reproduction. Their eggs are not lined by protective covering to control evaporation.
• They undergo aestivation or hibernation to prevent themselves from extreme cold and heat. This helps to overcome unfavourable conditions.
• Body of Amphibians is divided into a head and a trunk. The tail can be present or absent. But the neck is completely absent. 
• Skin is moist, smooth, and without scales. 
• Numerous mucous glands are located in the skin, which moistens the skin. When they respire through the skin, it is known as cutaneous respiration. 
• Most of them have two pairs of limbs. The forelimbs have four fingers, and the hindlimbs have five fingers.
• Presence of a well-developed digestive system with separate openings-mouth and anus. Salivary glands are absent in frogs.
• Alimentary canal urinary tract and genital ducts open outside through a common opening known as the cloaca,
• Respiration occurs by skin, gills, lungs, or via the buccopharyngeal cavity. 
• They are cold-blooded or poikilotherms.
• They have three-chambered hearts consisting of 2 auricles and one ventricle. Sinus venosus and Truncus arteriosus are both well-developed.
• Red blood cells or erythrocytes are biconvex, nucleated and oval.
• Presence of renal portal system and hepatic portal system.
• Kidneys can be mesonephric or opisthonephric. Mostly ureotelic in nature. 
• Skull has two occipital condyles. The tympanum represents the ear. Eyes have eyelids.
• Presence of 10 pairs of cranial nerves.
• Fertilization is external and takes place inside the water. Some have internal fertilisation also.
• Development is indirect through larva.
• For example, Ichthyophis, Salamandra, Rana tigrina, Bufo, Hyla.

Class Reptilia 

• Reptilia includes animals with creeping or crawling locomotion modes.
• The Mesozoic era is the golden age of reptiles.
• Study of reptiles is known as herpetology.
• They are cold-blooded or poikilotherms.
• Reptiles are the first terrestrial vertebrates.
• Body is divided into a head, neck, trunk, and tail.
• Exoskeleton is made up of horny epidermal scutes or scales.
• Skin is cornified, dry, rough, and non-glandular. Snakes and lizards shed their skin as skin casts.
• Limbs when present, they are 2 pairs and each limb has five digits..
• They have a complete alimentary canal that opens outside via the cloaca.
• Teeths are acrodont, pleurodont, and thecodont.
• Respiration occurs through the lungs.
• Heart is 3-chambered but crocodiles have 4-chambered hearts.
• Sinus venosus is not well developed and truncus arteriosus is absent.
• Red blood cells are oval and nucleated.
• Presence of one occipital condyle in the skull. Neck and thorax region contains ribs.
• Ribs are present in the neck and thorax region.
• Metanephric kidneys for excretion and osmoregulation.
• Presence of 12 pairs of cranial nerves. No external ear opening and tympanum represents the ear.
• Roof of the buccal cavity contains Jacobson’s organ. This is meant for olfaction.
• Fertilization is internal. They are unisexual organisms.
• They are mostly oviparous.
• Eggs are leathery and covered by shells made up of calcium carbonate.
• Development is direct with no larval stage.
• Presence of all three embryonic membranes amnion, chorion and allantois. Yolk sac is attached to the embryo.
• For example, Vipera, Bangarus, Naja naja etc.

Difference between Reptiles and Amphibians

FAQs : Reptiles And Amphibians

1. What are protostomes and deuterostomes?

Animals in which the mouth develops first are known as protostomes. For example, Platyhelminthes to Mollusca.

Animals in which the anus is formed first, and the mouth develops later are known as deuterostomes. For example, echinoderms, hemichordates, and chordates.

1. What is a blind sac body plan?

Animals in which a single opening serves as both mouth and anus. For example, Coelenterates to Platyhelminthes. 

1. What is a tetrapod?

Animals with four legs. Even though snakes lack legs, they did originate from animals with four limbs.