Invertebrates: Kingdom Animalia

• Phylum Porifera

  • These animals have a large number of openings or pores on their body.
  • They do not move from one place to another.
  • Ex- Sycon,Leucosolenia and Spongilla
• Phylum Coelenterata-Cnidarians

  • Coelenterates have a radially symmetrical body.
  • The body is hollow, tube-like and has only one opening called the mouth.
  • The mouth is a surrounded by a number of finger-like structures called tentacles. The tentacles have stinging cells called cnidoblasts that help them in anchoring, capturing prey and in self defence. That is why there called cnidarians.
  • Ex- Hydra, jellyfish, corals and sea anemone.
• Phylum Platyhelminthes

  • Flatworms are the simplest worms or animals without legs.
  • The body is thin and flattened it is bilaterally symmetrical.
  • They have only one opening through which they take in food and get rid of wastes.
  • Ex- tapeworms, Planaria and liver fluke.
• Phylum Nematoda

  • Their body is cylindrical, narrow and unsegmented (smooth surfaced) and bilaterally symmetrical.
  • They have an opening called mouth through which the food is pulled in and crushed. Another opening called anus is present near the tip of the body.
  • Thread like- Filarial worm Rounded worm - Hookworm
  • Ex- Pinworm, whipworm
• Phylum Annelida

  • They have a soft, cylindrical and bilaterally symmetrical body.
  • Their body has ring-like compartments called segments that help in movement.
  • They have special organs called nephridia for excretion.
  • Ex- earthworm, leech
• Phylum Arthropoda

  • The body is segmented and divided into three regions- head, thorax and abdomen.
  • The body has jointed legs.
  • The body has a tough outer covering called exoskeleton.
  • They have compound eyes. In arthropods, an image is formed in several pieces. This type of vision is called mosaic vision.
  • Arthropods are further classified into four sub-groups or classes.
  • Arachnida (scorpions and spiders)
  • Crustacea (lobsters,shrimps)
  • Myriapoda (centipedes and millipedes)
  • Insects (ants,beetles)
• Phylum Mollusca

  • They have a soft, unsegmented body, with an outer hard shell.
  • Ex- snail, octopus, oysters
• Phylum Echinodermata

  • Echinoderms have an unsegmented body.
  • There is no head and the body has five radial arms with sharp spines all over it.
  • They have a mouth on the lower side and an anus on the upper side.
  • They move with the help of tube-like feet.
  • Ex- starfish, brittle star and sea urchin.
• Population Pyramid

  Population pyramid refers to the graphical representation of the population structure based on an age wise increase or decrease of the male female population of a country. 


  A high birth and death rate the signifies the population structure of a developing country where there is a lack of better medical education and high standard of living.