Reproduction in Organisms

Reproduction is a process which enables a species to live generation after generation. There are two types of reproduction in organisms: Asexual Reproduction and Sexual Reproduction. The process of asexual reproduction does not involve the fusion of gametes and the offspring formed by asexual reproduction are identical and are referred to as clones. It is found in fungi, algae and some invertebrates. The other methods of asexual reproduction in animals are budding and gemmule formation. Prokaryotes and unicellular organisms reproduce asexually by the process of binary fission. In plants the asexual reproduction occurs with the help of runners, rhizomes, suckers, tubers, offsets, etc. These structures are capable of giving rise to new offspring. This type of asexual reproduction is called vegetative propagation. The sexual reproduction involves the formation and fusion of gametes. The sexual reproduction is mostly found in higher animals. Events of sexual reproduction can be divided into: pre-fertilisation, fertilisation and post-fertilisation events. Pre-fertilisation events include gametogenesis and pollination. Post-fertilisation events include the formation of zygote and embryogenesis. Plants can be monoecious and dioecious. The flowers may be bisexual or unisexual. The gametes are haploid in nature and are formed by the process of meiosis. The transfer of male gametes is one of the most essential events in sexual reproduction. In unisexual animals the transfer of gametes occur either by the process of copulation or by simultaneous release. In angiosperms, the transfer of gametes occurs by the process of pollination. The process of fertilisation or syngamy is followed by pollination. Fertilisation is the fusion of male and female gametes. Syngamy leads to formation of a specialised cell called zygote. The process of development of embryo from the zygote is called embryogenesis. In angiosperms, after fertilisation, ovary develops into fruit and ovules mature into seeds.

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