Human Reproduction & Fertilization: Definition & Examples

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Reproduction and Fertilization Definition

In order for the human species to continue to exist, mature adults must be able to produce viable children in order to secure the species’ survival and pass down genetic information from generation to generation. This is accomplished by reproduction. The following is a step-by-step breakdown of how reproduction works from start to finish.


Before fertilisation may take place, the building blocks for the original cell to grow into a full adult must be accessible. Adults create gametes through the process of meiosis. Each gamete includes half of the genetic information required to create a viable cell.

Fertilization, Reproduction, Gamete,2

1. Sperm, a gamete generated in the testes, is produced by human men.

2. Ovum is a gamete generated in the ovarian follicles by human females.

Every month, the female gamete is readily accessible to be fertilised by sperm and formed into a zygote for a brief period.

Fertilization, Reproduction, Gamete, 1


Half of the genetic information required to create children is contained in both gametes. They fuse together during fertilisation, ensuring that the children have all of the genetic information they need to thrive. In order for the semen (sperm) to be ejaculated and have the ability to fuse with the ovum, sexual contact is required.

Fertilization, Reproduction and Fertilization Gamete,

At the time of ejaculation, millions of sperm are discharged, and as they are expelled, their thread-like tails ‘swim’ towards the female egg. This sprint to the egg is powered by an ATP tank that supplies the necessary energy. Many sperm would have perished in their attempt to reach the egg after a long trip.

Some of them still have the ability to fertilise it. Each will cling to the ovum, but only one will be able to penetrate it. The acrosome (head) of the sperm contains enzymes that break down the egg wall. The egg secretes a variety of hormones after fertilisation to keep it from being overwhelmed by the millions of sperm attempting to fertilise it.


The united gametes, known as zygotes, undergo cell division within hours of fertilisation. The presence of a hormone called progesterone inhibits the production of more female eggs. The fertilised egg goes to the uterus within the first week following conception, where the zygote continues to grow in the form of an embryo.

Nucleotide Citations
  • Importance of sperm morphology during sperm transport and fertilization in mammals. Asian J Androl . Nov-Dec 2016;18(6):844-850.
  • Sperm competition and fertilization mode in fishes. Philos Trans R Soc Lond B Biol Sci . 2020 Dec 7;375(1813):20200074.
  • Sperm-egg interaction and fertilization: past, present, and future. Biol Reprod . 2018 Jul 1;99(1):134-146.
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