Animal Kingdom: Vertebrates
Table of Content
- Definition of Vertebrates
- Anatomy and Morphology of Vertebrates
- Classification of Vertebrates
- Agnatha/ Vertebrates lower Classification
- Class-Pisces
- Class – Amphibia
- Class- Reptilia
- Class – Aves
- Class – Mammalia
Definition of Vertebrates
Vertebrates represents the phylum Chordata. There are about 64,000 species known in this group. It includes jawless fishes and jawed vertebrates.
Anatomy and Morphology of Vertebrates/Vertebrates Characteristics
- Notochord found in chordates are replaced by segmented series of elements known as vertebrae.
- All basal vertebrates used gills for respiration, such as fishes. But higher vertebrates lack gills. They have lungs for respiration.
- Central nervous system is hollow with dorsal nerve cord. Vertebrates are only chordates with cephalization (brain is concentrated in head region).
- All vertebrates have ventral, muscular heart with a closed circulatory system.
- Reproduction is usually sexual.
- They are unisexual animals with a pair of gonads.
- They possess two pairs of appendages.
- Presence of paired pharyngeal gill slits.
- They are bilaterally symmetrical.
- Triploblastic in nature.
- They are coelomate with well- developed organ system and organization.
- They possess post anal tail at some or the other stages of life.
- Kidneys are excretory organs which maintains the osmoregulation of the body.
Classification of Vertebrates
Phylum Chordata is divided into- Urochordata or Tunicata, Cephalochordata and Vertebrata.
Fig.1. Classification of vertebrates
Agnatha/Vertebrates lower Classification
- Is a superclass of jawless fish.
- It comprises of both cyclostomes and extinct conodonts and ostracoderms.
- They have notochord in larval and adult stages.
- They are characterized by absence of paired fins.
- They are cold-blooded with cartilaginous skeleton.
- The heart is two chambered.
For example, Myxine (Hagfish) and Petromyzon (Lamprey).
Fig.2. Cyclostomes- Hagfish and Lamprey
Class-Pisces
It includes subclass- Chondrichthyes and Osteichthyes
Chondrichthyes
- Cartilaginous fishes are included in this subclass.
- Notochord persist throughout the life.
- Gill slits are present but without gill cover (operculum).
- Presence of Placoid scales.
- They are predatory animals.
- Absence of air bladder due to which they swim continuously.
- They possess two chambered heart with one auricle and one ventricle.
- Electric organs are present in Torpedo.
- Some have poison sting such as Trygon.
- They have separate sexes.
- Internal fertilization and generally viviparous.
Fig.3. (a)-Scolidon (b)-Pristis
For example, Carcharodon (Great white shark), Trygon (Sting ray), Scoliodon (Dog fish) etc.
Osteichthyes
- Marine as well as freshwater fishes are included in this subclass.
- They have bony endoskeleton.
- They have gill with operculum.
- Skin is with Ctenoid scales.
- They are cold-blooded animals.
- Presence of air bladder.
- Heart is two chambered with one auricle and one ventricle.
- External fertilization and organisms are oviparous in nature.
Fig.4. (a) Hippocampus (b) Catla
For example, Pterophyllum (Angel fish), Hippocampus (Sea horse), Freshwater – Labeo (Rohu)
Class – Amphibia
- They live in aquatic as well as in terrestrial environment.
- Possess two pairs of limbs.
- Body is divided into head and trunk.
- Skin is without scales.
- Eyes possess eyelids.
- Cloaca is the common opening of alimentary canal, urinary and reproductive tract.
- Gills, lungs, and skin acts as respiratory organs.
- Heart is three chambered with two auricles and one ventricle.
- Fertilization occurs in water, that is, external.
- Sexes are separate with indirect development.
- They are oviparous in nature.
Fig.5. Amphibians
For example, Salamandra (Salamander), Bufo (Toad), Rana (Frog) etc.
There are three subclasses of Amphibia are- Labyrinthodontia, Lepospondyli and Lissamphibia.
Subclass Lissamphibia consists of three orders-
- Caudata- For example, Salamander.
- Anura- For example, Frogs and toads.
- Apoda- For example, Caecilians.
Class- Reptilia
- They have crawling mode of locomotion.
- Mostly they are terrestrial in nature.
- They have dry cornified skin with epidermal scales or Scutes.
- They are without external ear openings.
- Heart is three chambered but some have four chambered heart such as Crocodiles.
- They have the ability to regulate their body temperature, that is, Poikilotherms.
- Sexes are separate with internal fertilization.
- Development is direct and oviparous in nature.
Fig.6. Reptilia
For example, Crocodilus (Crocodile), Testudo (Tortoise), Alligator (Alligator), Hemidactylus (Wall lizard), Poisonous snakes – Naja (Cobra)
Subclasses of Reptilia are as follows- Anapsida, Parapsida, Diapsida and Synapsida.
- Subclass Anapsida includes order Chelonia. For example, Tortoise and Turtles.
- Subclass Parapsida, for example, Protosaurs.
- Subclass Diapsida includes orders such as Rhyncocephalia (tuatara), Squamata (Lizards and snakes) and Crocodilia (Crocodiles).
- Synapsida, for example, ss.
Class – Aves
- Characteristic feature is the presence of feathers in all birds except flightless birds.
- They have beak.
- They have forelimbs which are modified into wings.
- Hind limbs serve for walking, clasping and swimming.
- Presence of oil glands at the base of the tail.
- Endoskeleton is bony with hollow long bones. Hollow bones helps during flight.
- Birds have additional chambers in digestive system known as crop and gizzard.
- Heart is four chambered with two auricles and two ventricles.
- They are warm-blooded animals.
- Lungs are respiratory organs.
- Fertilization is internal with separate sexes.
- Development is direct and oviparous in nature.
Fig.7. Aves
For example, Aptenodytes (Penguin), Neophron (Vulture), Corvus (Crow), Columba (Pigeon)
There are basically two subclasses- Archeornithes and Neornithes.
The subclass Archeornithes includes single genus fossil bird having a single species, Archaeopteryx lithograpthica.
Neornithes includes Odontognathae and Neognathae.
Class – Mammalia
- They are adapted for polar environment, deserts, forests, mountains, grasslands, and dark caves.
- The most important feature is presence of milk producing glands known as mammary glands.
- They possess two pairs of limbs which are adapted for walking, jumping, climbing, burrowing, swimming, flying, and running.
- Presence of characteristics hairs on the skin.
- Presence of external ear known as Pinnae.
- Heart is four chambered with two auricles and two ventricles.
- They maintain their constant body temperature, so considered as homoiothermous.
- Lungs are the respiratory organs.
- Development is direct with viviparous nature.
- Fertilization is internal.
Fig.8. (a) Ornithorhynchus (b) Macropus (c) Pteropus (d) Balaenoptera
For example, Rattus (Rat), Canis (Dog), Felis (Cat), Macropus (Kangaroo), Pteropus (Flying fox), Camelus (Camel), Oviparous-Ornithorhynchus (Platypus)
Subclasses of Mammalia
- Subclass Eutheria (Placental mammals).
- Subclass Metatheria (marsupials).
- Subclass Prototheria.
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