Here is a list of eleven important phylum:- 1. Phylum Protozoa 2. Phyllum-Porifera 3. Phylum Cnidaria 4. Phylum Ctenophora 5. Phylum Platyhelminthes 6. Phylum Nemathelmlnthes 7. Phylum Annelida 8. Phylum Arthropoda 9. Phylum Mollusca 10. Phylum Echinodermata 11. Phylum Chordata.
1. Phylum Protozoa (Approximately 30,000 Known Species):
Unicellular Animals like Amoeba, Paramoecium, Monogystis and Malaria parasite. Protozoa are microscopic in size. Each individual consists of only one cell which has to carry on all the vital activities. They are abundantly found in water containing decaying organic matter. Some, such as the dysentery amoeba and the malaria parasite, live within other animals. Still others live in damp soil, or in fresh water, or in the sea.
The single-celled condition is an important feature which sets the protozoa apart from all other animals. These unicellular creatures have therefore been placed in the subkingdom protozoa, which includes only one phylum, the protozoa. The remaining phyla of animals, all of which are many-celled, comprise the sub- kingdom metazoa.
2. Phyllum-Porifera (Approximately 5000 Known Species):
Sponges.
These are pore-bearing sedentary animals found mostly in the sea. A few species occur in the fresh water but none on the land. The sponges, like plants, are attached to a substratum. The outer surface of the sponge is perforated by numerous pores and the body wall is supported by a framework which is composed of lime, or of silica or of an organic substance called spongin.
3. Phylum Cnidaria (Approximately 10,000 Known Species):
Hydra, Jelly-Fishes, Sea-Anemones and Corals.
Most of the cnidaria are marine but Hydra is found in fresh water. Some, such as the corals and sea-anemones, are attached to a substratum; others are slow moving or adapted for drifting in the water. All are radially symmetrical. This means that the animal is the same all round, and has no right or left side. It is symmetrical around a median vertical axis, and can be divided into similar halves by a number of vertical planes.
Body wall is composed of two layers; it encloses a central digestive cavity which communicates with the exterior by only one opening, the mouth. Thus, the cnidarian body is essentially a two-layered hollow sac opening by the month; the sac may be tubular, as in hydra, or saucer-shaped, as in jelly fish. There are movable arm like structures near the mouth, called tentacles, which carry peculiar stinging cells for stunning the prey.
4. Phylum Ctenophora (Approximately 80 Species):
Beroe, Hormiphora, Pleurobrachia.
The phylum derives its name from two Greek words—Ktenos= comb, phoros= bearing. Ctenophores are all marine. They have bi-radially symmetrical bodies. They possess eight meridionally placed ciliated plates. They resemble the cnidarians on many counts but differ from them in not having the nematocysts. Their ectomesoderm is gelatinous and bear mesenchymal muscle cells. They possess a specialised aboral sense organ and the tentacles bear adhesive cells. All are planktonic.
5. Phylum Platyhelminthes (Approximately 6500 Known Species):
Flat-worms, Flukes and Tape-worms.
These are flat, un-segmented, worm-like creatures with soft and bilaterally symmetrical body. In a bilaterally symmetrical animal there is a right side and a left side, a fore end and a hind end, a dorsal or back surface and a ventral or front surface. There is only one plane of symmetry by which the body can be divided into two equal halves.
Leaf-like liver-flukes and ribbon-like tapeworms are parasites but there are several free-living species, marine as well as fresh-water. Digestive canal is incomplete, with only one opening, the mouth; there is no anus. Excretion of waste products is effected by peculiar flame cells.
6. Phylum Nemathelmlnthes (Approximately 10,000 known Species):
Round-worms.
These are cylindrical, un-segmented, worm-like animals with soft, bilaterally symmetrical body, tapering at both the ends. Digestive canal is complete, with two openings, a mouth in front and an anus behind; it is a straight tube running through the body from end to end. Most of the group are aquatic. A few inhabits damp soil. Others, such as hook-worms, thread-worms and filaria worms are parasites of man and cattle.
7. Phylum Annelida (Approximately 7500 Know Species):
Earth-worms, Leeches and Sand-worms.
These are true worms with soft, elongated, bilaterally symmetrical body, divided into a series of ring-like segments or meta- meres. The annelids are, therefore, known as the segmented worms. The annelidan body is built on the tube-within-a-tube plan.
The outer tube represents the body wall and the inner tube represents the digestive canal. The two tubes are separated from one another by a space called body cavity or coelom. Most of the annelids, such as the sand-worms, are marine; others, like the leeches, are fresh-water; but the earth-worm is sub-terrestrial.
8. Phylum Arthropoda (Approximately 750,000 Known Species):
Prawns, Crabs, Cockroaches, Centipedes, Millipedes, Scorpions, and Spiders.
Arthropods are bilaterally symmetrical, segmented animals with soft parts of the body protected by a hard chitinous external skeleton. Each segment of the body bears paired legs or appendages which are jointed. This phylum is the largest of the animal phyla and includes nearly three-fourths of all the known species of animals.
9. Phylum Mollusca (Approximately 90,000 Known Species):
Clams, Oysters, Snails, Cuttle-fishes and Octopus.
Molluscs are un-segmented and without appendages. The soft parts of the body are enclosed in a Hard calcareous shell, as in snails and oysters. A fleshy muscular foot for locomotion is often present. Many of the molluscs are marine, some are fresh-water, and a few like the garden snails are terrestrial.
10. Phylum Echinodermata (Approximately 6,000 Known Species):
Starfishes, Sea-urchins, Sea-cucumbers and Sea-lilies.
Echinoderms are characterised by spiny skin. All are marine, inhabiting the shore and bottom of the sea. A few such as the sea-lilies are attached; but the majority are free to move about. Locomotion is very sluggish and effected by peculiar structures called tube-feet. This is the only phylum possessing a water- vascular system. The body is radially symmetrical and star-like as in starfishes, brittle-stars and basket-stars.
11. Phylum Chordata (Approximately 100,000 Known Species):
Balanoglossus, Ascidians, Amphioxus and Vertebrates.
The chordates possess a stiff supporting rod, called notochord. Leaving aside a few lower forms, such as balanoglossus, ascidians and amphioxus, all chordates are vertebrates. Vertebrates possess the backbone which forms the supporting skeleton for the long axis of the body.
Vertebrate body is bilaterally symmetrical and is typically composed of head, trunk and tail. There are two pairs of appendages, either in the form of paired fins or limbs, or wings. They comprise the highest animals and include man.
Vertebrates are divided into the following classes:
(1) The cyclostomata including lampreys and hag fishes which are round- mouthed and without a lower jaw;
(2) The chondrichthyes or cartilaginous fishes such as sharks and electric rays;
(3) The osteicthyes or body fishes like Bhetki and Rohu;
(4) The amphibians such as toads, frogs and salamanders with moist, naked skin;
(5) The reptiles including snakes, lizards, tortoises and crocodiles with scales on their outer surface;
(6) The aves or birds with feathers and wings for flight;
(7) The mammals including duck-billed mole, kangaroo, guinea-pig and man, with hairy skin and with young ones fed by the mother with her own breast-milk.