The important Phylum’s under which all the animals are divided are given below:
1. Protozoa:
These are single called animals with a simple organization, the nutrition is heterotrophic. Most are free living but some are parasitic like Plasmodium. Ex: Amoeba, Paramoecium
2. Porifera (The sponges):
Most of them are marine and unmovable. The body matrix has calcareous and siliceous spicules embedded in the gelatinous material. Though some cell differentiation is present, tissue organization is absent. Body has two layers of cells. All are marine forms and locomotion is absent in the adult forms.
Water and food is drawn through collar cells and expelled through osculum. All the forms are hermaphorites and they have great regenerative power. This is called a dead end phylum as it has not given rise to any other group of organisms.
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3. Coelenterates (Cnidarians):
Consists of sea anemones, corals and jelly fish. These are also mainly marine animals with hydra a fresh water form. These are radically symmetric and body wall diploblas- tic (body wall composed of two layers of cell, and outer ectoderm and an inner endoderm). They have stinging cells called Nematocyst. Cnidarians have 2 basic body forms – polyp and medusa. Ex-jelly fish, corals and sea anemones.
4. Flatworms (Platy helminthes):
These are parasitic in nature. These are triploblastic and exhibit bilateral symmetry. These are unsegmented worms with pointed ends. Sexual reproduction is also present due to their bisexual nature. Many are important animal parasites.
5. Nematoda (Roundworms):
They have tube with in tube body plan with mouth, pharynx, intestine and anus. A psuedocoelom is present and sexes are separated. Many nematodes are plant parasites: Ex: root knot nematode
6. Annelida (Segmented worms):
They have true body cavity and bilateral symmetry with a chitinous cuticle. True metameric segmentation is present. A developed circulatory system is found. Both bisexual and male/female forms are present.
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Ex: Earthworm, Leech.
7. Arthoropods (Jointed legged animals):
Largest group of animals and cuticle of chitin is present. Body is bilaterally symmetrical, segmented and divided into head, thorax and abdomen. Jointed legs, compound eyes, sensory structures called antennae are present.
8. Mollusca (Soft bodied, shelled animals):
These are unsegmented, triploblastic coelomates. Body is soft and fleshy and divided into a head, ventral muscular foot and dorsal visceral hump. Over the hump the skin secrets a calcareous shell. They have no limbs. Breathe through gills, but land forms like snails have lungs. Ex: Squid, Octopus, Oyster, Mussel, cuttle fish, snail and slug etc.
9. Echinoderms (Spiny skinned animals):
All are marine forms with radially symmetrical body. A distinctive water vascular system and tube feet (for locomotion) are present. A calcareous exoskeleton is present. Adults show five way radial symmetry. Ex: star fish and sea urchins.