Yogy's biology

  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 -  Amphibia Reptilia Aves and 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 r

  4. Kingdom Animalia - part 13 - Subphylum : Vertebrata and its divisions,supaerclass Pisces and its two classes Subphylum : Vertebrata In these chordates, notochord is replaced by  cartilaginous or bony vertebral column.  It is divided into two divisions -  Agnathostomata (no jaws) and  Gnathostomata (jaws present). 1. Division : Agnathostomata : This division includes the  lowest or most primitive vertebrates , which are  without jaws.  They include only one class of living vertebrates - the  Cyclostomata. Class : Cyclostomata (Cyclos : Circular, Stoma - mouth) Lat/Grk. e.g.  Petromyzon (Lamprey), Myxine (Hagfish). Cyclostomes are  jawless and eel-like  animals.  Skin is soft, smooth containing unicellular mucus glands, but no scales.  Median fins are present  but paired fins are absent. They are  ectoparasites .  They have sucking and circular mouth without jaws.  Cranium and vertebral column  made up of  cartilage . Digestive system lacks stomach. Respiration occurs by  6 to 15 pa

  4. Kingdom Animalia - part 12 - Phylum : Chordata Phylum : Chordata Chordates are characterised by - presence of cartilagenous notochord at least in early embryonic life presence of gill slits in the pharyngeal (neck) region presence of hollow, dorsal nerve cord running through out the length of body and  ventral heart. Phylum Chordata is divided into three subphyla- Urochordata Cephalochordata and Vertebrata.  Urochordata and Cephalochordata are collectively called  Protochordates . a. Subphylum : Urochordata or Tunicata : e.g.  Herdmania, Salpa, Doliolum. These are also called as  tunicates or ascidians.  They are exclusively marine. Body is soft and covered by 'test' or 'tunic' which is made up of  tunicine .  Notochord is present only in the  tail of larva , hence the name, urochordata. Notochord is lost during metamorphosis. Pharynx has many  gill slits.   Closed circulatory system  is present.  Development is indirect. b. Subphylum : Cephalochordata : e.g.  Bran

  4. Kingdom Animalia - part 11 - Phylum : Hemichordata Phylum : Hemichordata (Hemi : Half, Chordata : Rod) e.g.  Balanoglossus, Saccoglossus. Earlier, this Phylum was considered as  sub-phylum of Chordata  because buccal diverticulum was considered as  notochord . But, now it is placed as a separate phylum of Non-chordata.  These are exclusively marine animals, usually living at the bottom of sea in burrows.  Mostly these are free living but the animals like  Rhabdopleura  are sedentary.  Body is soft, vermiform, unsegmented and divided into three parts - proboscis collar and  trunk. Buccal cavity gives rise to  rod-like buccal diverticulum  which is considered as  notochord  by some scientists. Alimentary canal is  complete, straight or 'U' shaped.  Respiration occurs by  numerous gills , arranged in two longitudinal rows, present in the pharyngeal region.  Gills open by  gill slits. Circulatory system  is  simple and open type.  Excretion  occurs with the help of  glomerulus

  4. Kingdom Animalia - part 10 - Phylum : Echinodermata Phylum : Echinodermata (Echinus - Spines, derma - skin) e.g.  Asterias (Sea star), Cucumaria (Sea cucumber), Echinus (Sea urchin), Antedon (sea lily), Ophiothrix (Brittle star). These are exclusively marine, solitary, sedentary or free-living and gregarious, benthic. These are  radially symmetrical  animals with  pentamerous symmetry.   Body may be spherical, elongated or star-shaped. Endoskeleton is made up of  calcareous ossicles. Spines  are present on the body, hence the name echinodermata.  The body is without definite body divisions, instead, there are two sides as oral and aboral. The peculiar character is presence of water vascular system in which water enters through madreporite. This system is used in locomotion, food capturing, respiration, etc.  Digestive system is complete.  Mouth is ventrally present on oral surface and anus on aboral surface. Respiration is performed by  peristomial gills, papillae, respiratory tre

  4. Kingdom Animalia - part 09 - Phylum : Mollusca Phylum : Mollusca (Mollis : soft) e.g.  Pila, Bivalve, Octopus (devil fish), Sepia (cuttle fish), Chaetopleura (Chiton), Pinctada (Pearl oyster), L oligo (Squid), Aplysia (Sea hare), Dentalium (Tusk shell). This is  second largest phylum.  Molluscs are either free living or sedentary.  They are aquatic or seen in marshy places. Few are terrestrial.  These are soft bodied and show tube within tube body plan.  These are  bilaterally symmetrical , but few are asymmetrical due to torsion (twisting).  Body is divisible into  head, foot and visceral mass.  Visceral mass is enclosed in thick muscular fold of body wall called  mantle .  Mantle secretes a hard calcareous shell, the shell may be external or internal or absent.  Muscular foot is present on ventral side. Digestive system is well developed, complete with  anterior mouth and posterior anus.  Buccal cavity has a rasping organ called  radula  which is provided with transverse rows of

  4. Kingdom Animalia - part 08 - Phylum : Arthropoda Phylum : Arthropoda (Arthros : Joint, Podos : leg) : e.g.  Cockroach, Butterfly, Scorpion, Millipede , Prawn. This is  largest phylum  of kingdom animalia.  These animals have jointed appendages, hence the name - Arthropoda. These are  omnipresent  and solitary or colonial, most of them are free-living (Barnacles are sedentary).  Few are  parasitic and sanguivorous  (female mosquito, bed bug).  Their body is  bilaterally symmetrical, triploblastic, eucoelomate, metamerically segmented with tube within tube body plan and organ-system level of organization.  Body is covered by tough,  non-living chitinous exoskeleton . Hence, they need periodic  moulting (ecdysis).  Body is divided into head,  thorax and abdomen. Digestive system is  complete . Circulatory system is of  open type , blood flows through  body cavity (haemocoel).  Respiratory organs are  gills, trachea, book lungs, book gills. Excretion takes by  green glands, Malpighian