[Biology Class Notes] on How Does Reproduction Happen in Humans? Pdf for EXAM

Living organisms need food, and shelter to survive and grow. But the most important part of the life cycle of an organism is reproduction. Now, what is reproduction? In general, reproduction is the process of creating an offspring. This ensures the continuity of life and the species as a whole. It is one of the important aspects of life continuity on earth. Hence, for the continuity of their own species, humans also reproduce. Reproduction in humans occurs by the fusion of male and female gametes, which is a type of sexual reproduction. 

Let’s look into human reproduction in more detail.

Modes of Reproduction

There are two modes of reproduction, namely: Asexual Reproduction and Sexual Reproduction.

In this type of reproduction only single organism gives birth to an organism. Most of the processes of asexual reproduction include budding, fission, spore formation, fragmentation, regeneration and parthenogenesis. In this case, the genetic material of the offspring is usually identical to the parent. Example: many bacteria and fungi.

In sexual reproduction, the female and the male gametes fuse to birth an offspring. Here, the genetic material of the offspring has characteristics of both the parents. Example: Most of all mammals.

Reproduction In Human Beings

Humans do sexually reproduce mammals and so they are viviparous. The male and female gametes fuse together to give rise to an embryo. The fertilisation of the gametes and the development of an embryo until the childbirth occurs within the female. Since humans are viviparous, they give birth to a child instead of laying eggs. Reproduction in humans is a complex process and the human reproductive system has a vital role in it.

Human Reproductive System

The human reproductive system takes in the role of the male and the female reproductive system. The male reproductive system is responsible for the formation of the male gametes and also the deposition of these gametes into the female reproductive system. The female reproductive system, on the other hand, is responsible for the formation of the female gametes and the protection and the nourishment of the fetus until childbirth. The degree of variation in the male and female reproductive system is vast. Both have high levels of differentiation not only in the primary sex organs and sex characteristics but also in the secondary sex characteristics as well.

 

Events of Reproduction in Humans

Reproduction in human beings can be listed in the following events:

Gametogenesis

↓

Insemination
↓

Fertilisation

↓

Implantation

↓

Gestation

↓

Parturition

Gametogenesis: 

This event is characterized by the formation of the male and female gametes. A sperm is a male gamete, while an ovum is a female gamete. A fusion of these two gives rise to zygote formation. The formation of sperm takes place inside the testis which is a male reproductive organ, after a meiotic division of male germ cells. The formation and release of ovum happens in the ovaries, which are female reproductive organs and also after the meiotic division of the female egg cells.

Insemination: 

This event is characterized by the act of mating or sexual intercourse, which serves as a way for the transfer of sperms into the female genital tract. Once, into the genetical tract, the ovum released into the fallopian tube is fused with the sperm cell which leads to the formation of the embryo.

Fertilisation: 

This event is characterized by the fusion of the sperm and the ovum. This event takes place inside the fallopian tube which is a part of the female reproductive system. Zygote formation takes place after fertilization.

Implantation: 

In this step, the zygote is transformed into a blastocyst, a cellular body made up of 16 cells. After the development of the blastocyst, it attached itself to the uterine wall until the birth of the baby. The lining of the uterus by then has prepared itself for the development of the blastocyst.

Gestation: 

After the attachment of the blastocyst, the development of the embryo which was moving from zygote to blastocyst stage, begins in this fixed position. This development takes place for a period of weeks and the embryo gets transformed into a child.

Parturition: 

This event is characterized by the delivery of the child from the mother’s body.

 

The entire cycle of events of how reproduction is happening in humans after fertilization is shown in the below diagram:

These events of reproduction in humans with their estimated period of time are shown in a tabulated form as below: