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.

    Comments

    Post a Comment

    Popular posts from this blog

    2. Systematics of Living Organisms part 03 - Units of Classification

      2. Systematics of Living Organisms part 03 - Units of Classification Units of Classification : Species : Species is the  principal natural taxonomic unit , ranking below a genus and denoted by  latin binomial  (considered as the basic) unit of classification.  It is a  group of organisms  that can interbreed under natural condition to produce fertile offspring.  It was thought to be an  indivisible, stable and static unit.   However in the modern taxonomy, subdivision of species such as  sub-species, varities and populations  are seen and given more importance. Genus :  Genus is a taxonomic rank or category  larger than species  used in the biological classification of living and fossil organisms.  Genus is a  group of species   bearing close resemblance to one another in their morphological characters but they do not interbreed.  e.g.  Tiger, Leopard, Lion  all three belong to sam...
    Read more

    2. Systematics of Living Organisms - part 04 - Nomenclature

      2. Systematics of Living Organisms - part 04 - Nomenclature Nomenclature : The art of naming the objects is in fact, a science called  nomenclature.  All living organisms are known by a particular name. 1.Vernacular / Local names / Common names:  Widely distributed organisms have a large number of common names.  Pansy (Viola  tricolor  L.)  grown in most European and American gardens has about 50 common English names.  In a multilingual country like India, almost all useful plants have local names which differ from language to language and even from dialect to dialect.  As in Ayurveda,  mango (Mangifera  indica  L.)  is known by over 50 different names, all in the Sanskrit language. Hence the common names obviously have limited usage and for universal applications, a unique name for a particular individual is very much essential. 2. Scientific Names :  To overcome the difficulties raised by common names, scient...
    Read more

    2. Systematics of Living Organisms - part 05 -Salient features of Five Kingdoms

    Image
      2. Systematics of Living Organisms - part 05 -Salient features of Five Kingdoms  Salient features of Five Kingdoms : 1. Kingdom Monera : It contains unicellular organisms with prokaryotic cellular organization.  Monera includes  unicellular prokaryotic organisms. These are omnipresent.  They are found in all types of environment which are not generally inhabited by other living beings.  Few are  photoautotrophs or chemoautotrophs ; but  majority are heterotrophic  in nature.  These organisms do  not have well defined nucleus . DNA exists as a simple double stranded circular single chromosome called as  nucleoid. Smaller circular molecules of DNA as extrachromosomal genetic elements called  plasmids  are often present.  Cell wall is made up of  peptidoglycan  (also called  murein ) which is a polymer of sugars and amino acids. Membrane bound organelles e.g.  mitochondria, chloroplast, endopla...
    Read more