Fertilization and reproduction are two interlinked aspects.Reproduction can be defined as the biological process of producing a new individual or an offspring identical to the parents. This process ensures the increase in the number of individuals of a species when conditions are favourable. It is one of the fundamental characteristics of living things and an essential life process.
Living organisms make sure that they continue to reproduce for their existence on the Earth. Reproduction may occur either asexually or sexually. There is a significant difference between sexual reproduction and asexual reproduction. The sexual mode of reproduction is a more complex process as compared to the asexual mode. One crucial difference is the process of Fertilization. It is known to be the main stage of sexual reproduction which is absent in asexual mode.
Reproduction in Human Beings
Generally, all human beings undergo a sexual mode of reproduction wherein, two parents are involved in producing a new individual. Offspring are produced by the fusion of gametes (sex cells) from each parent. Hence, the newly formed individual will be different from parents, both genetically and physically. Human reproduction is an example of sexual reproduction.
In human beings, both males and females have different reproductive systems; hence, they are known to exhibit sexual dimorphism. Males have testes- also called testicles, while the females have a pair of ovaries.
Fertilization in Animals
The process in which there is a fusion of sperm with the egg also known as the Ovum to produce Zygote is called Fertilization. It is the vital and primary stage of sexual reproduction. During sexual intercourse in humans, a penis ejaculates millions of sperms into the vagina of the woman. Sperms travel through the uterus to oviducts. At the oviduct, one out of million sperms being released fertilizes the released ovum. A fertilized egg develops into a zygote. Without the fusion of gametes, sexual reproduction is futile. This process doesn’t occur in asexual reproduction.
Fertilization in most of the animals is similar to that of humans. Animals also produce gametes for fusion. But the fusion of gametes may take place inside or outside the body. Based on this, fertilization can be categorized into two parts – Internal and External Fertilization.
Internal Fertilization
For sexual reproduction, male penis insertion into the vagina of a woman is important. A male inserts his penis into the vagina of a woman, after which the penis secretes sperm into the female reproductive tract to fuse with the egg. If the fusion takes place within the female parent, then it is known as Internal Fertilization. In both humans and animals, the fusion of gametes takes place internally. In internal fertilization, a zygote is formed within the mother’s body and gets its nourishment from her.
External Fertilization
External fertilization is the process when the fusion of sperm and egg takes place outside a female parent. Very less humans and animals go for this kind of fertilization. Some of the animals which practice external fertilization are- fish, frogs, etc. In this process, the female parent deposits her eggs in an external environment, and later, the male parent ejects his sperm over them by which fusion takes place.
In the process of external fertilization, the gametes whose fusion takes place externally, face a lot of challenges. Since the eggs and sperms are deposited and kept in an external environment, the chances of fusion are very less. There are possibilities that predators may end up eating the eggs and zygote that if formed.