How do organisms Reproduce?

Reproduction in Organisms can be defined as, the replication in the making of copies of a particular organism. The cells use chemical reactions to construct copies of their DNA, as a result, two copies of the DNA are created. To ensure this, one cell divides into two cells, each cell containing its own DNA and cellular apparatus, now, these two cells will be identical, but we cannot make the DNA copy 100% identical. There must be some variation in the chemical, which means organisms cannot create precise replicas of themselves.

Also Read: Structure of DNA

Key Terms: Reproduction, sexual reproduction, asexual reproductions, DNA, reproduction organism

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What is Reproduction?

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The process of Reproduction can be described as the process through which the same kind of species are created. This process of reproduction is based on the concept of DNA creation.

There are two types of Reproduction-

• Asexual Reproduction.
• Sexual Reproduction.

Modes of Reproduction

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Types of Reproduction

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Here are mainly two types of Reproduction:

1. Asexual Reproduction: This one can be further divided in five categories, i.e.-
   • Fission
   • Budding
   • Regenerating
   • Fragmentation
   • Spore Formation

Asexual Reproduction:

Asexual Reproduction is a method of reproduction that involves one organism( a single organism reproduces two or compound organisms on its own), this is seen in all unicellular organisms, some multicellular organisms and a few nature.

Asexual Reproduction Process

Types of Asexual Reproduction:

1. Fission: It is a unicellular organism.
   • When fission results in two daughter cells, it is called Binary Fission (eg.paramecium) 
   • When it results in many daughter cells it is called multiple fission (e.g. Plasmodium). 

Binary Fission Process

Multiple Fission Process

2. Budding: It is a type of asexual reproduction in which the new organism is created from a bud outgrows from any part of teh parent cell. a little cyst-moreover structure. In some cases the bud may remain attached to the parent, till it matures (example-yeast) or may split and become an abnormal individual (example-hydra).

Process of Budding in Hydra

3. Regeneration: There are few organisms that, if cut in pieces, are able to grow on its own again. This kind of asexual reproduction is called Regeneration. 

Regeneration Process

4. Fragmentation is the process by which an organism gets fragmented into smaller pieces and each fragment grows into a mingle auxiliary organism. E.g. Planaria, Hydra

Process of Fragmentation

5. Spore formation: Organisms such as fungi make spores that can mass into combined add-on individuals when remote from their fruiting body. This process is called Spore Formation.

Process of Spore Formation

Sexual Reproduction

Sexual Reproduction is the mode of reproduction that involves two individuals; one male and one female. They produce sex cells or gametes which integrate to form any more organism.

• Fertilization is the process of combining the nucleus of a male gamete as soon as the nucleus of a female gamete. In humans, each gamete has half the number of the quantity 46 chromosomes that the body requires(23 chromosomes within a gamete are referred to as a haploid).
• When egg and sperm cells are included in fertilization, they unite the two sets of chromosomes. Hence, the maternal chromosomes from the egg cell and the paternal chromosomes from the sperm cell pairing takes place.
• The zygote will epoch into an embryo. It includes DNA from both- the mom and the father, therefore will have a blend of characteristics of both parents.
• Sexual reproduction uses a type of cell disaffection called meiosis, which creates gametes, such as sperm and egg cells. The process of meiosis happens in the male and female reproductive organs.
• After interphase: Two meiotic divisions occur, i.e. the cell divides twice to form four gametes. Each gamete has half the number of chromosomes found in body cells (one chromosome for each pair), and is therefore known as a haploid.
• All gametes genetically vary from one to another, and the resultant cell is called a zygote. It is diploid as it has two copies of every one of chromosome allowance - one came from the sperm cell and one came from the egg cell.

In sexual reproduction, two parents are needed during the whole process as the nuclei of the male and female gametes are collective in order to make a zygote. This process is known as fertilization.

The gametes are:

• eggs (female)
• sperm (male)

The offspring produced in sexual reproduction, involves the mixing of two genetic patterns.

Sexual Reproduction in Animals:

1. Male Reproductive System: The formation of male gametes or sperm(haploid in nature) in testes is known as spermatogenesis. Seminiferous tubules are the site for spermatogenesis whereas testis produces a male hormone known as testosterone needed for the male secondary sexual characteristics as well as for spermatogenesis.

Sperm (Male Reproductive System)

2. Female Reproductive System:

   • Sperm enter into the female vagina at the time of sexual intercourse, from where the sperm reaches the fallopian tube where it fuses the ovary to form a zygote. This is known as fertilization.
   • Then the zygote divides to form an embryo and the embryo gets implanted into the uterus. The embryo development occurs in the uterus to form the fetus.

Mother supplies nutrition to the growing fetus via the placenta. The placenta helps in the exchange of nutrients, gasses and the removal of excretory products. The development of a child inside the womb of the mother takes place for about 9 months. Then the rhythmic uterine contraction leads to the delivery of the baby outside the female body.

Female Reproductive System

Sexual Reproduction in Plants:

In the case of the sexual reproduction of plants, the whole process takes place through the process of Pollination. A flower includes male sex organs- stamens, and the female sex organ- pistils. A part of stamen called pollen, needs to be transferred into a specific part of pistil, called- stigma.

Plants may have two types of Pollinations-

• Self Pollination- in this case it fertilizes its ovules with its own pollen.
• Cross pollination- in this case the winds or animals or bugs does the pollination.These animals or insects are called Pollinators.

Reproduction in Plants

Also Read: Sexual Reproduction in flowering plants

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Contraceptive Methods

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Understanding the reproductive system is also a part of reproductive health awareness as Reproductive health deals with the prevention of STDs and unwanted pregnancy.

Contraceptives are devices that help to prevent unwanted pregnancy and help avoid STDs. They can be of various types such as mechanical barriers, hormonal/chemical methods, surgical methods, etc.

• Sexual intercourse Interruptus is a very unreliable contraceptive method where the sexual intercourse is stopped before the male ejaculates inside the female reproductive tracts.
• Rhythm Method is an unreliable method of contraception where sexual intercourse is avoided when the female is fertile and the chances of fertilization are very high.
• Condoms are one of the most effective methods of contraception which provides a mechanical barrier that stops the semen from entering the female tract preventing pregnancy and possibility of contracting STDs.
• Diaphragms are barriers that can be added inside the female reproductive tracts to stop the entry of semen inside the female tract and thus prevent pregnancy.
• Contraceptive pills are chemical methods of contraception which change the level of hormones in the body that prevents the release of the ovum from the ovaries.
• Emergency pills are those pills which can be taken after sexual intercourse to avoid pregnancy. They quickly change the level of hormones in the body and prevent a successful implantation even if the egg gets fertilized.
• IUD stands for Intrauterine Device, a device that is inserted into the uterus, changing its shape and preventing successful implantation of the zygote.
• Sterilization is a surgical method of going permanently sterile ( can be done in both males and females). In males, it is called vasectomy and whereas in females, it is called tubal ligation.

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Things to Remember

• Reproduction is a process through which any organism maintains their species line.
• Reproduction process can be divided into two types- Asexual Reproduction and Sexual Reproductions.
• Asexual Reproduction can be further divided into five categories- Fission, Budding, Regeneration, Fragmentation, and Spore Formation.
• Sexual reproduction includes two different organisms- one female and one male.
• Animal and Plant sexual reproductions are different from each other.

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