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Friday, 27 January 2017

Animal Kingdom : Classification

CLASSIFICATION OF ANIMALS

1. Phylum Porifera-

  • Members of this phylum are commonly known as sponges. Mostly marine, asymmetrical and have cellular level of organization.
  • They have water transport or canal system. Water enters through minute pores, Ostia into central cavity Spongocoel, from where it goes out through Osculum.
  • Nutrition, respiration and excretion is performed by pathway of water transport system.
  • Skeleton made up of spicules or spongin fibres.
  • Egg and sperms are produced by same organism (hermaphrodite). Asexual reproduction by fragmentation and sexual reproduction by gametes formation.
  • Fertilisation internal and development is indirect.
  • Example- Sycon, Spongilla.

2. Phylum Cnidaria ( Coelenterate)-

  • They are aquatic, mostly marine, sessile, free swimming, radially smmetrical animals.
  • They exhibit tissue level of organization, diploblastic, coelomate with single opening.
  • They show two types of body called polyp and medusa.
  • Polyp is sessile, fixed, and cylindrical, without gonads such as Hydra, Adamsia and Medusa is free swimming, umbrella like having four gonads like Aurelia and Jelly fish.
  • Some cnidarians exhibits both forms (Obelia), polyp produce medusa asexually and medusa produce polyp sexually.

3. Phylum Ctenophora-

  • Commonly known as the Comb Jellies or Sea Walnuts.
  • Exclusively marine, diploblastic, radially symmetrical, with tissue level of organization. Body bears eight ciliated comb plates which help in locomotion. 
  • Bioluminescence (to emit light) is present in Ctenophores. Hermaphrodite, fertilisation external, development indirect, 
  • Example- Ctenoplana, Pleurobranchia.

4. Phylum Platyhelminthes (The Flat worms)

  • Dorso-ventrally flattened body, bilaterally symmetrical, triploblastic, acoelomate with organs levels of organization.
  • Hooks and sucker are present in parasitic forms. Flame cells help in osmoregulation and excretion. 
  • Fertilisation is internal, development is indirect, hermaphrodite.
  • Example- Taenia, Planaria, Fasciola.

5. Phylum Aschelminthes ( The Round Worm)

  • They may be free-living, aquatic, terrestrial or parasitic in plants or animals.
  • Bilaterally symmetrical, triploblastic, pseudo coelomate.
  • Alimentary canal is complete with well-developed muscular pharynx.
  • Dioecious, females are longer than male.
  • Example- Ascaris (round worm), Wucheriria(filarial worm), Ancyclostoma.

6. Phylum Annelida

  • Aquatic or terrestrial, bilaterally symmetrical, segmented with organ system level of organization. 
  • Aquatic Annelids like Nereis possesses lateral appendages parapodia, for swimming. Nephridia help in osmoregulation and excretion. Neural system consists of paired ganglia.
  • Dioecious (Nereis) or monocious (earthworm, leech)
  • Example- Pheretima (earthworm), Hirunidaria (Blood sucking leech).

7. Phylum Arthropoda

  • Largest phylum of animals which includes insects. Organ system of organization, triploblastic, coelomate, bilaterally symmetrical with chitinous exoskeleton.
  • Body consists of head, thorax and abdomen, jointed appendages (jointed feet). Respiratory organs are gills, book lungs or tracheal system with open circulatory system.
  • Excretion through malpighian tubules, sense organs antenna or eyes. Fertilisation internal, mostly oviparous.
  • Example :
  • Economically important- Apis (honey bee), Bombyx (silk worm). Vectors- Anopheles, Ades, Culex (mosquito).
  • Living fossils- Limulus (king crab)

8. Phylum Mollusca

  • Terrestrial or aquatic, organ level of organization, bilaterally symmetrical, triploblastic and coelomate.
  • Body divided into head, muscular foot and visceral hump. Unregimented and covered with calcareous shell.
  • Feather like gills are present between hump and mantle.
  • Mouth contains file like rasping organ for feeding called radula.
  • Example- Pila, Octopus.

9. Phylum Echinodermata (The Spiny Skinned Animals)

  • Endoskeleton of calcareous ossicles, marine with organ system of organization.
  • Triploblastic, coelomate, presence of water vascular system help in locomotion, capture of food and respiration.
  • Sexes are separate, fertilisation is external and development is indirect.
  • Example- Asterias (Star fish), Cucumaria (Sea cucumber), Antedon (Sea lily).

10. Phylum Hemichordata

  • Worm-like marine animals with organ system of organization, bilaterally symmetrical, triploblastic and coelomate animals. 
  • Body is cylindrical, composed of anterior proboscis, a collar and a long trunk. Open circulatory system, respiration by gills, excretory organ is proboscis glands. Sex separate, fertilisation external, indirect development.
  • Example- Balanoglossus, Saccoglossus.

11. Phylum Chordates

  • Presence of notochord, a dorsal hollow nerve chord and paired pharyngeal gill slits.
  • Bilaterally symmetrical, triploblastic, coelomate with organs system levels of organization.
  • Closed circulatory system, ventral heart, post-anal tail is present.
  • In Urochordata, notochord is present only in larval tail. In Cephalochordate it extends from head to tail and persists throughout the life.
  • Vertebrata possesses notochord in embryonic period which is replaced by vertebral column in the adults.
  • Sub-phylum Vertebrata is further divided into two division Agnatha ( lacks jaw) and Gnathostomata ( bears jaw).
  • Gnathostomata is further divided into two super class- Pisces ( bears fins) and Tetrapoda (bears limbs).



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