Jain Biology

Author(s): Jethalal S Zaveri, Mahendramuni
Publisher: Jain Vishva Bharati

Page 54

fission. It is binary if it results in two daughters and multiple if the result is more than two daughters. The division of the cytoplasm is accompanied by the mitotic division of the chromosomes. Both binary and multiple types of fission are usual and characteristic method of reproduction among protozoans. In parasitic Protozoa where multiple type is more common, the products are called schizonts. The malarial parasite forms schizonts inside red blood cells of the host. When they are liberated, each one penetrates a fresh cell.
(b) Fragmentation : When processes similar to fission take place in some metazoans also, they are called fragmentation. In sea anemones and most of the corals, it is the normal method.
(c) Budding : This process is quite common among coelenterates such as hydra. It results in the production of a group of new celis which eventually form new individuals. The rate of growth of buds is determined by the availability of food.
(d) Regeneration : In this process restoration of a complete, functioning individual from some part of the parent body other than the gamete, takes place. Protozoa, Porifera, Coelenterata and Planaria can regenerate fully from as small as 0.5% of the parent body. Planarians show remarkable powers of regeneration. If an individual is cut into two, the anterior end will regenerate a tail and the posterior end develops a new head. A middle piece will regenerate both a head and a tail, earthworms also have considerable powers to regenerate. In general the regenerative capacity is greater in animals of lower grades of evolution. The exact mechanism of the regulation of regeneration is far from fully understood.
SEXUAL REPRODUCTION
In addition to the asexual methods of reproduction described above, some protozoans also show sexuality accompanied by reproduction. As stated before, the basic characteristic of sexual reproduction is the fusion of two specialized sex cells called gametes. The body formed by the fusion of the two gametes is called a zygote and the term common for all types (and there are many) of sexual reproduction involving a zygote is ZYGOGENESIS JAIN BIOLOGY
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