Biology
Topic: Meaning And Types Of Sexual Reproduction
Table of Contents
- Meaning Of Sexual Reproduction
- Types Of Sexual Reproduction
What Is Sexual Reproduction?
Sexual reproduction is the type of reproduction which involves the fusion of the male gametes and the female gametes to form a zygote which layer develop to a young offspring. In other words, in sexual reproduction, offspring are produced by fusion of two different sex cells (gametes) which usually come from two different parents.
Types of Sexual Reproduction
There are two major types of sexual reproduction. These are conjugation and fusion of gametes.
1. Conjugation
Meaning: Conjugation is a simple type of sexual reproduction which occurs in some lower organisms such as Mucor, Rhizopus, Paramecium and Spirogyra. Conjugation is the process by which nuclear material is passed from one cell to another.
In Spirogyra, for example, conjugation starts with two filaments called conjugants coming together to lie side by side. Lateral outgrowth starts to develop opposite each other from opposite cells in the two filaments. The outgrowth meet and the separating walls dissolve to form a continuous channel called conjugation tube. Meanwhile, the cytoplasm of each cell shrinks away from the cell walls and round up to form a gamete.
One of the gametes regarded as the male migrates through the conjugation tube into other cell. The cytoplasms of the two cells fuse, the nuclei also fuse and a zygote is formed. After sometime, the zygote or zygosphere will germinate and a new filament is formed.
2. Fusion of Gametes (Fertilization)
Meaning: Fusion of gametes is the union of the haploid male and female gametes to produce diploid organisms called zygote. The process of this union of the gametes to form this zygote is called fertilization.
In higher animals, these gametes are formed in special organs called gonads. The male gametes is called spermatozoa or simply sperm are produced in the tests by meiotic cell division called oogenesis. These male and female gametes are brought together during mating and they unite or join together by a process of fertilization to form a diploid zygote which later develop into a new organism.
In higher plants, male and female gameted are also produced. The flowers are the reproductive units in plants. The male gametes called pollen grains are produced by anthers while the female gametes called ovules are produced by the ovary of the flower. The pollen grains and the ovules fused together during fertilization to form a zygote. After fertilization, the ovules form the seeds while the ovary becomes the fruit.