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Protozoans, kinds of protozoansProtozoans are the simplest kinds of animals. They consist of a single, minute cell of protoplasm (the living substance of all plants and animals) containing a nucleus, the control center of the protozoans. All other animals contain many cells. Protozoans live in the sea and fresh water, in damp soil, and in other animals, including man. Protozoans cause some diseases, including malaria, sleeping sickness, and a form of dysentery.
Single-celled animals of one of the kinds of protozoans include jelly-like amoeba and globigerina. Globigerina float about in warm seas and their shells pile up on the sea bed to form chalk There are four kinds of protozoans. Flagellates move through water by using long whip-like projections. Sarcodines include amoeba, which move by extending pseudopods (amoeba), and radiolarians and foraminiferans, which float about in the water and have shells of silica or chalk. Sporozoans are parasites and depend completely on their hosts. The malaria-causing parasite belongs to this group. Ciliates have small hairs called cilia that they wave about to move.
Protozoans reproduce by cell division, in which one cell splits into two new ones; by budding, in which part of the cell breaks away to form a new cell; and by dividing into smaller cells called spores, which may pair up before growing into new animals. The nucleus of the parent cell is always divided among the new protozoans. You can read these articles also: |
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Wikipedy.com @ - Online Encyclopedia |
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