Reproduction is a fundamental and characteristic process carried out by all living entities. From microorganisms up till the most advanced animals in the animal kingdom – the humans, all exhibit reproduction. Without reproduction, there would be no traces of existing species. One of the two modes of reproduction is the sexual mode of reproduction, which is one of the most impactful and significant modes. It is a process by which a new offspring is born from two parents as a result of the transfer of genetic information from both parents. Species can either be isogamous(similar gametes) or anisogamous(dissimilar gametes) to reproduce sexually. In the case of anisogamous reproduction, usually, there are two parents, the female and the male. To reproduce, both contribute gamete(sex cells) which contains a single set of chromosomes and is called a haploid cell which will make up the future offspring. Half of the offspring’s genetic information is contributed by a single parent. Most of the animals including humans reproduce this way. The sex cells produced by the males are called sperm while the sex cells produced by the female is called an egg or ova. Both the sperm and egg fertilize within the female reproductive system in the event of sexual intercourse.
When the egg is fertilized by the sperm it results in the formation of the zygote(union of gametes) and hence is in the stage of conception. The zygote undergoes continuous division (mitosis and meiosis) after which it implants itself in the uterus of the female to develop into the embryo after undergoing a few phases which are later addressed to as the fetus. The fetus in the uterus of the mother is nourished and grows through the gestation period, which in humans is typically for a period of 9 months. This period, however, varies in different animals. Post the complete development of the fetus in her uterus, the female parent delivers the baby so that it grows and thrives on its own. Through the process of in-vitro fertilization, in humans, eggs can be fertilized externally.
Few animals, especially few aquatic animals, fertilize their eggs externally by releasing their eggs and sperms in the water medium, where they fuse to fertilize. Internal fertilization takes place in reptiles and birds post which eggs are laid, from which new creatures hatch after a certain period of time. Pollination in plants is a mode of sexual reproduction where pollen grains come in contact with the stigma, which can either be carried out through self-pollination or cross-pollination modes depending upon the plant. Visit BYJU’S, for more information on sexual reproduction of living entities and related topics.