4. Kingdom Animalia - part 14 - Superclass : Tetrapoda

 

4. Kingdom Animalia - part 14 - Superclass : Tetrapoda

Subphylum : Vertebrata

2. Division : Gnathostomata

Superclass : Tetrapoda :

• These animals bear two pairs of appendages. 
• Some animals like snakes are secondarily limbless.
• Superclass tetrapoda includes four classes namely - 

1. Amphibia
2. Reptilia
3. Aves and
4. Mammalia.

1. Class : Amphibia (Amphi : both, bias : life) :

• e.g. Rana (Frog), Bufo (Toad), Salamandra (Salamander), I chthyophis (Limbless amphibian), H yla (Tree frog).
• Amphibia include the animals which live on land as well as in water (fresh water only). 
• They are poikilothermic animals. 
• Body is differentiated into head and trunk. 
• Neck and tail is usually absent in many adults with few exceptions. 
• Two pairs of limbs arise from pectoral and pelvic girdles respectively. These help in locomotion. 
• Skin is moist, glandular with mucous glands. 
• Exoskeleton is absent.
• Eyelids are present. 
• Tympanum represents the ear. 
• Excretory products, digestive wastes and gametes are released through common chamber called cloaca. 
• Circulatory system is of closed type. 
• Heart is three chambered and ventral in position. 
• RBCs are biconvex and nucleated. 
• Respiration is by skin, lungs and buccopharynx. 
• Nervous system is well developed. 
• Sexes are separate. These are oviparous. 
• Fertilization is external. 
• Development is indirect through aquatic larval stage. 
• They show metamorphosis.

2. Class : Reptilia (Repere : to creep or to crawl) :

• e.g. Naja naja (Cobra), H emidactylus (Wall lizard), Chelonia ( Turtle), Crocodilus (Crocodile), Testudo (Tortoise), Chameleon (Tree lizard), Bangarus (Krait), Vipera (viper).
• Reptilia includes crawling animals.
• These are the first true terrestrial vertebrates. 
• Few may be aquatic or semi-aquatic, also found in marshy area. 
• Locomotion occurs by limbs. 
• The limbs are pentadactyl and digits bear claws. 
• Limbs help the animal to walk or creep. 
• Snakes are limbless. Snakes crawl on their belly. 
• Reptiles are poikilotherms. 
• Skin is dry, non-glandular and covered by exoskeleton of epidermal scales or scutes, shields or plates.
• Lizards and snakes shed their skin periodically. 
• Tympanum is present. 
• Heart has two complete auricles, but ventricles are incompletely partitioned. So heart is not perfectly four chambered (except crocodile). 
• Brain is well developed. The olfactory lobes and cerebellum are better developed than those of amphibians.
• Sexes are separate and show prominent sexual dimorphism.
• Fertilization is internal. 
• They are oviparous (except viper, it is viviparous) and show parental care. .

3. Class : Aves (Avis : bird):

• e.g. Columba (Pigeon), Psittacula (Parrot), Flight less birds like Struthio (ostrich), Kiwi, Aptenodytes (Penguin), Corvus (crow), Neophron (Vulture), Passer (sparrow).
• Forelimbs are modified into wings for flying (some birds have lost the capacity to fly e.g. Ostrich), hind limbs are used for walking, clasping tree branches and running. 
• Aquatic birds have webs between their toes (e.g. Duck).
• Body is streamlined (Boat shaped) to reduce resistance during flight. 
• These are homeotherms i.e. their body temperature remains constant.
• Exoskeleton is made up of feathers. 
• Scales are present on hind limbs.
• Body is differentiated into head, neck, trunk and tail. 
• Skin is thin, dry, non-glandular except oil gland at the base of tail (uropygialgland). 
• Bones are hollow (pneumatic) with air cavities to reduce body weight. 
• Jaws are without teeth and modified into beak. 
• Crop and gizzard are present in digestive system.
• Blood is red in colour due to presence of red blood cells. 
• RBCs are biconvex and nucleated.
• Heart is perfectly four chambered. They show double circulation. 
• Respiration takes place by lungs, having air sacs to increase the buoyancy.
• Brain is enlarged and has well developed cerebellum for equillibrium. 
• Sexes are separate with prominent sexual dimorphism. These are oviparous. 
• Fertilization is internal. 
• Parental care is very well developed. 
• Seasonal migration is seen in some birds.

Special features :- 

• The urinary bladder is absent. 
• The female shows presence of only left ovary and left oviduct. 
• This helps to reduce body weight.

4. Class : Mammalia (mammae : breasts, nipples) :

• e.g. Bat, Rattus (Rat), Macaca (Monkey), Camelus (Camel), Whale, Human being, Cannis (dog), F elis (Cat), Elephas (Elephant), Equus (Horse), Pteropus (flying fox). Oviparous - Ornithorhynchus (Platypus).Viviparous - Macropus (Kangaroo).
• Mammalia includes the animals having mammary glands (milk producing glands) for the nourishment of young ones. 
• These are omnipresent. 
• Mostly terrestrial, some are aquatic and few are aerial and arboreal.
• Limbs are the organs of locomotion and used for walking, flying, climbing, burrowing, swimming, etc. 
• Body is differentiated into head, neck, trunk and tail. 
• These are homeotherms. 
• Exoskeleton is in the form of hair, fur, nails, hooves, horns, etc. 
• Skin is glandular having sweat glands and sebaceous glands (oil glands).
• Mammary glands are modified sweat glands.
• They have external ear (pinna). 
• They show heterodont dentition. 
• RBCs are biconcave and enucleated. 
• Blood is red in colour. 
• Heart is ventral in position and four chambered.
• Respiration takes place by lungs. 
• Brain is highly developed. Cerebrum shows a transverse band called corpus callosum. 
• Few mammals are oviparous (e.g. Duck billed platypus). 
• Some have pouches for the development of immature young ones, these are called marsupials e.g.Kangaroo. 
• Majority of mammals are placental and viviparous.