Question

Give characteristics of all phylums under Animalia with examples.

Answer 1

Kingdom Animalia is divided into eleven major phylums.

1. Phylum Porifera

• Primitive multicellular organisms with cellular level of organisation
  
• They are generally marine and asymmetrical
  
• Digestion is intracellular.
  
• The body is supported by a skeleton made up of spicules or spongin fibres.
  
• Sexes are not separate, thus they are called hermaphrodite (egg and sperms are in the same individual).
  
• Sponges reproduce asexually by fragmentation and sexually by formation of gametes.
  
• Fertilisation is internal
  
• Development is indirect having a larval stage which is morphologically distinct from the adult.
  
• Examples: Sycon, Spongilla, etc.
  

2. Phylum - Colenterata (Cnidaria)

• They are aquatic, mostly marine, sessile or free-swimming.
  
• Radially symmetrical animals
  
• Exhibit a tissue level of organisation
  
• They are diploblastic.
  
• Digestion is intracellular and extracellular.
  
• They have stinging capsules present on the tentacles and the body. These Cnidoblasts are used for anchorage, defense and for capture of prey.
  
• They exhibit two basic body forms called polyp (sessile and cylindrical) and medusa (umbrella-shaped and free-swimming.
  
• Examples: Physalia, Adamsia, etc.
  

3. Phylum - Ctenophora

• Commonly called sea walnuts or comb jellies
  
• Exclusively marine
  
• Radially symmetrical
  
• Diploblastic organisms with tissue level of organisation
  
• Has eight external rows of ciliated comb plates for locomotion
  
• Digestion is both intracellular and extracellular.
  
• Exhibits the property of bioluminescence.
  
• Sexes are not separate.
  
• Reproduction takes place only by sexual means.
  
• Fertilisation is external with indirect development.
  
• Examples: Pleurobrachia and Ctenoplana
  

4. Phylum – Platyhelminthes

• Dorso-ventrally flattened body, hence called flatworms
  
• Endoparasites found in animals including human beings
  
• Bilaterally symmetrical
  
• Triploblastic and acoelomate animals
  
• Organ level of organisation
  
• Hooks and suckers are present in the parasitic forms. Some of them absorb nutrients from the host directly through their body surface.
  
• Flame cells help in osmoregulation and excretion.
  
• Sexes are not separate.
  
• Fertilisation is internal and development is through many larval stages.
  
• Some members like Planaria possess high regeneration capacity.
  
• Examples: Taenia (Tapeworm), Fasciola (Liver fluke).
  

5. Phylum – Aschelminthes

• They are circular in cross-section, thus, are called roundworms.
  
• They may be free-living, aquatic and terrestrial or parasitic in plants and animals.
  
• Organ-system level of body organisation.
  
• Bilaterally symmetrical
  
• Triploblastic and pseudocoelomate
  
• Alimentary canal is complete with a well-developed muscular pharynx.
  
• An excretory tube removes body wastes from the body cavity through the excretory pore.
  
• Sexes are separate (dioecious), i.e., males and females are distinct.
  
• Often females are longer than males.
  
• Fertilisation is internal and development may be direct (the young ones resemble the adult) or indirect.
  
• Examples: Ascaris (Round Worm), Wuchereria (Filaria worm), Ancylostoma (Hookworm).
  

6. Phylum – Annelida

• Can be aquatic (marine and freshwater) or terrestrial, free-living, and sometimes parasitic.
  
• Has organ-system level of body organisation
  
• Exhibit bilateral symmetry.
  
• Triploblastic, metamerically segmented and coelomate animals.
  
• Their body surface is distinctly marked out into segments or metameres
  
• Longitudinal and circular muscles help them in locomotion.
  
• Aquatic annelids like Nereis have lateral appendages, parapodia, which help in swimming.
  
• Closed circulatory system
  
• Osmoregulation and excretion are done through nephridia.
  
• Reproduction is sexual.
  
• Examples: Nereis, Pheretima (Earthworm) and Hirudinaria (Blood sucking leech).
  

7. Phylum – Arthropoda

• Largest phylum, includes insects
  
• They have organ-system level of organisation.
  
• They are bilaterally symmetrical, triploblastic, segmented and coelomate animals.
  
• Body is covered by chitinous exoskeleton.
  
• The body consists of head, thorax and abdomen.
  
• They have jointed appendages (arthros-joint, poda-appendages).
  
• Respiratory organs are gills, book gills, book lungs or tracheal system. Circulatory system is of open type.
  
• Sensory organs like antennae, eyes (compound and simple), statocysts or balance organs are present.
  
• Excretion takes place through malpighian tubules.
  
• Mostly dioecious.
  
• Fertilisation is usually internal.
  
• They are mostly oviparous.
  
• Development may be direct or indirect.
  
• Examples: Apis (Honey bee), Laccifer (Lac insect), Anopheles, Culex and Aedes (Mosquitoes)
  

8. Phylum – Mollusca

• Terrestrial or aquatic (marine or fresh water)
  
• Have an organ-system level of organisation.
  
• They are bilaterally symmetrical, triploblastic and coelomate animals.
  
• The body is covered by a calcareous shell.
  
• It is unsegmented with a distinct head, muscular foot, and visceral hump.
  
• They have gills present in a mantle cavity which have respiratory and excretory functions.
  
• The anterior head region has sensory tentacles.
  
• Usually dioecious and oviparous
  
• Indirect development
  
• Examples: Pila (Apple snail), Pinctada (Pearl oyster), Sepia (Cuttlefish), etc.
  

9. Phylum – Echinodermata

• They are called Echinodermata because they have endoskeleton of calcareous ossicles.
  
• Marine
  
• Organ-system level of organisation
  
• Adult echinoderms are radially symmetrical but larvae are bilaterally symmetrical.
  
• They are triploblastic and coelomate animals.
  
• Digestive system is complete with mouth on the lower (ventral) side and anus on the upper (dorsal) side.
  
• They have water vascular system which helps in locomotion, capture, and transport of food and respiration.
  
• An excretory system is absent.
  
• Sexes are separate.
  
• Reproduction is sexual.
  
• Fertilisation is usually external.
  
• Development is indirect with free-swimming larva.
  
• Examples: Asterias (Star fish), Echinus (Sea urchin), etc.
  

10. Phylum – Hemichordata

• It consists of a small group of worm-like marine animals.
  
• Organ-system level of organisation
  
• They are bilaterally symmetrical, triploblastic and coelomate animals.
  
• The body is cylindrical and is composed of an anterior proboscis, a collar and a long trunk.
  
• Circulatory system is of open type.
  
• Respiration takes place through gills.
  
• Excretory organ is proboscis gland.
  
• Sexes are separate. Fertilisation is external.
  
• Development is indirect.
  
• Examples: Balanoglossus and Saccoglossus
  

11. Phylum – Chordata

• Possess a notochord, a dorsalhollow nerve cord and paired pharyngeal
  
• gill slits.
  
• These are bilaterally symmetrical, triploblastic and coelomate
  
• Have organ-system level of organisation.
  
• They possess a post-anal tail
  
• Closed circulatory system
  
• Examples: Ascidia, Scoliodon