Introduction to Phylum Chordata:
- Every chordate should possess four fundamental characters at some point of life.
- Presence of solid, stiff notochord
- Single tubular dorsal hollow nerve cord
- Pharyngeal gill slits
- Post-anal tail
General features of chordates:
- Bilaterally symmetrical body
- Organ system level of body organization
- Triploblastic
- Complete alimentary canal (tube within tube body plan)
- Presence of true coelom (Enterocoelom)
- Closed circulatory system
Subphylum Vertebrata:
Vertebrata belongs to division Gnathostomata: (gnathos = jaw; stoma =mouth).
Vertebrata includes two superclasses:
- Superclass Pisces
- Superclass Tetrapoda
Superclass Pisces (Fishes):
- Study of Pisces is called Ichthyology.
- All fishes in superclass pisces are true fishes.
- Pisces have streamlined body to reduce drag and friction as they move through water, allowing for faster, more efficient swimming and greater energy conservation
- Pisces show primary aquatic adaptation
- Fishes have dorsal, caudal, anal, pectoral and pelvic fins for locomotion. In addition, Pectoral and pelvic fins are paired fins that provide stability and balance while swimming.
- Pisces are ectothermic (poikilothermic) i.e cold blooded animals that can change their body temperature according to their surroundings.
- Pisces possess lateral line system for detecting water current.
- Pisces are mostly gill breathers but few are lung breathers.
Superclass Pisces have two classes
Based on the ednoskeleton
Class Osteichthyes (Bony Fishes)
- Habitat: Both fresh water and marine
- Endoskeleton is bone
- Scales: Comb-like ctenoid scales
- Four pairs of gills with operculum
- Male copulatory organ clasper is absent
- Swim bladder is present.
Subclass Sarcopterygii
Bear muscular lobe in fins
Order Dipnoi (Lung fish)
Lung breathers
Eg: Neoceratodus (Australian lung fish)
Protopterus (African lung fish)
Lepidosiren (Latin American lung fish)
Order Living fossil order
- Eg: Latimeria
Subclass Actinopterygii
- Ray-finned fishes
- Eg: Anguilla (Eel)
- Labeo rohita (Rohu)
- Catla catla (Katla)
- Exocoetus (Flying fish)
Class Chondrichthyes
- Habitat: Exclusovely marine
- Endoskeleton is cartilage
- Scales: Placoid scales
- Five to seven pairs of gills without operculum
- Male copulatory organ clasper is present
- Swim bladder is absent
- Ampulla of Lorenzini (thermoreceptor) is present
Subclass Elasmobranchi
- Five to seven pairs of gills, without operculum
- Eg: Scoliodon (Dog fish), Sphyrna (Hammer head shark), Pristis (Sawfish), Rhinobatus (Guitar fish), Trygon (Sting ray), Astrape, Torpedo (Electric ray)
Subclass Holocephali
- Four pairs of gills, with operculum
- Eg: Chimaeria (Rat fish/ Rabbit fish/ Ghost shark)
Superclass Tetrapoda:
Class Amphibia
- Study of amphibian is called Herpetology.
- They can live in both land and water but not found in desert and marine
- Habitat
- Poikilothermic
- Forelimb bears 4 digits
- Hind limb bears 5 digits with webbed feet
- Skin of frog is smooth, glandular (mucus gland)
- Skin of toad is rough, warty, glandular (poisonous gland)
- They undergo winter sleep (hibernation) and summer sleep (aestivation)
- Tadpole is ammonotelic
- Adult amphibians are mostly ureotelic
- They have sticky, bifid, evertible tongue
- Sexes are separate
- Fertilization is external (Salamander: internal)
Classification based on the body division
Subclass Anura
- Body divisible into head and trunk (no tail in adult, present in tadpole)
- Example: Tree frog (Hyla), Flying frog (Rhacophorus), Midwife toad (Alytas)
Subclass Urodela (Caudata)
- Body divisible into head, neck, trunk, tail
- Example: American Salamander (Ambystoma)
Subclass Apoda (Caecilians)
- Limbless amphibians (Caecilians)
- Example: Ichthyophis
Class Reptilia:
- Study of reptiles is called herpetology
- Poikilothermic
- Skin dry, rough, non-glandular
- Poison gland is present (Parotid gland in maxilla)
- Exoskeleton is spines
- Sexes are separate
- Fertilization is internal
- They are mostly oviparous; some viviparous (Chameleon, Phyranosoma)
- Direct development
- Mostly uricotelic
- Respiration by lungs
- Jacobson organ (Vomero-nasal organ) aids in olfactoreception
Classification of class amphibian based on presence of temporal fossa
Subclass Anapsida (Turtles & Chelonians)
They have no temporal fossa
- Order Chelonia
- Eg: Tustedo (Terrestrial turtle)
- Terrapins (Freshwater turtle)
- Chelone (Marine turtle)
Subclass Parapsida (Extinct Reptiles)
- Extinct reptiles
- Eg: Dinosaur
Subclass Diapsida
Order Rhynocephalia
- Eg: Sphenodon
Order Squamata
- Eg: Hemidactylus (Wall lizard), Calotes (Garden lizard), Draco (Flying lizard), Phyranosoma (Horn toad), Heloderma (Poisonous lizard)
Order Crocodilia
- Eg: Crocodile, Gharial, Alligator
Class Aves:
- Study of aves is called ornithology
- They have streamlined body to enhance their ability to fly by minimizing resistance against air currents,
- Beak is modified snout.
- Forelimbs are modified into wings for flight.
- Hindlimbs are for swimming, walking, perching
- Skin is non-glandular
- Preen gland (uropygidium) in tail secretes oil that makes feathers of birds waterproof
- Respiration occurs by lungs and air sac (accessory respiratory organ)
- Endoskeleton includes pneumatic bone, keel sternum (breast bone), pygostyle
- Exoskeleton includes feathers, claws, scales
- They are uricotelic
- Direct development
- They have well developed cerebellum and optic lobes
- Comb-like structure in retina (Pecten) imparts sharp monolocular vision and nutrition to eye balls
Classification is based on whether bird is extinct or not.
Sub-class Archaeorinthes
- Teeth is present in beak
- Tail is elongated
- Claws present in wings
- Eg: Archaeopteryx
Sub-class Neorinthes
- No teeth
- Tail is short
- Unclawed wings
- Eg: Starling bird, American Golden Plover, Siberian bird
Class Mammalia:
- Study of mammals is called mammology
- Skin glandular (sebaceous, sweat and mammary gland)
- Diaphragm present
- Extra abdominal testes
- Pinna present
- Corpus callosum present
- Mostly viviparious except Prototherians
Classification based on presence of marsupium and placenta
Sub-class Prototheria
- Connecting link of reptiles and mammals
- Egg laying mammals
- Poisonous
- No placenta
- Common opening for urine and stool (cloaca)
- No pinna
- Testes abdominal
- No nipple in mammary gland
- No corpus callosum
- Eg: Duck billed Platypus (Ornithorhynchus), Spiny ant eater (Echidna)
Sub-class Theria
Infra class Metatheria (Marsupials)
- Bears marsupium
- No placenta
- Eg: Kangaroo, Opposum
Infra-class Eutheria (Placental mammals)
- Bear placenta
Important orders of Eutheria:
Proboscidia
- Upper incissor modified into tusk
- Eg: Elephus maximus (Asian elephant), Loxodonta (African elephant)
Rodentia (largest order)
- Small mammals
- Incissor teeth grow throughout life
- Eg: Rat, Mouse, Porcupine
Lagomorpha
- Canine teeth absent
- Eg: Rabbit, Hare
Dermaptera
- Skin folds laterally forming patagia
- Eg: Flying Lemur
Chiroptera
- Forearm fold to form patagia
- Eg: Flying fox (Pteropus)
- Horse shoe bat (Rhinolophus)
Cetacea
- Hindlimb absent
- Forelimb modified into flipper
- Secondary aquatic adaptation
- Blubber present
- Eg: Whale, Dolphin
Carnivora
- Strong canine teeth
- Eg: Lion, tiger, dogs, cats
Perispdactyla
- Single toed hoofed
- Eg: Horse, Zebra, One-horned rhino
Artiodactyla
- Two-toed
- Eg: Cow, goat, deer, giraffe
Primates
- Plantigrade
- Prosimians: Lemur, Tarsiers, Lorises
- Simians: Apes, Human, Monkey
- Insectivora
- Eg: Mole, Hedgehog, Shrew
Edentata
- Eg: Pangolin, Sloth, Armadillo, Anteater