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1. Phylum Protozoa :
The cell of these unicellular animals possesses contractile as well as food vacuoles. Digestion is intracellular, i.e.., within the cell. The locomotion is achieved either by temporary pseudopodic as in amoeba or by whiplike flagella as in Euglena, or by cilia (hair-like processes) as in paramoecium. Reproduction is normally asexual by binary or multiple fission. Examples: Amoeba, found in the mud of ponds; no definite shape just a mass of protoplasm bounded by a thin membrane with a nucleus in the centre; contractile vacuole is excretory in function.
Paramoecium (slipper anmalcule) has an unchanging and definite slipper-like shape; there are two nuclei—a small one surrounded by a larger one; towards either end of the body there is a contractile vacuole surrounded by a few radiating canals; found in fresh water with decaying vegetation.
Euglena contain chlorophyll as in plant cells (botanists regard them as algae). Due to the lashing movements of the flagellum it moves in water.
2. Phylum Porifera :
All the sponges are included in this phylum; aquatic animals mostly marine; though multicellular are incapable of any movement; cells are not organized into tissues and organs. There is neither a mouth nor a digestive tract; reproduction is asexual (by budding or by formation of gemmules) and sexual.
3. Phylum Coelenterata :
Hydra, Jelly fish, Sea-anemone, and Corals are some examples of this phylum. They are aquatic, mostly marine, multicellular and radi-ally symmetrical animals; they exist in two forms—i) a tubular body having anterior mouth or (ii) an umbrella shaped body with tentacles. There is a nervous system in the form of a nerve net formed of scattered nerve cells (protoneurons) and joined together by nerve processes. Reproduction is by asexual method (budding and fusion) and also by sexual method.
JAIN BIOLOGY Jain Education International
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