Wednesday, January 14, 2009

Sexual Reproduction in Animals

Sexual reproduction is the most common method of reproduction in higher forms of animals. Sexual reproduction involves the formation of male and female gametes and their fusion resulting in the formation of a zygote. The gametes are produced after the meiosis and are haploid and the fusion product of gametes, the zygote, is diploid. The process of syngamy or fertilization causes the mixing of genetic materials of the male and female parent.

Animal development commonly proceeds through several stages. Gametogenesis, during which the egg and sperm mature within the reproductive organs of the parents. Fertilization, which begins when a sperm penetrates an egg and is completed when the sperm and egg nuclei fuse forming a zygote. The zygote undergoes mitotic cell divisions that form the early multicellular embryo, which develops into an organism gradually through different stages. Sexual reproduction thus shows the formation diploid and haploid stages in the life cycle alternately.

The two types of gametes-the male gametes and female gametes-may be produced in the same body or separately by the male and female parent. When separate male and female individuals are present in a species, they are called unisexual organisms. All higher forms of animals and humans are examples. Some species are capable of producing both male and female gametes in the same organisms (body) and such species are known as bisexual or hermaphrodites. Some lower forms of organisms such as earthworms, tapeworms, snails, and some fish belong to this class.

Tags : Bio Technology, Bio Genetics, Sexual Reproduction

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