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How Do Organisms Reproduce?

Reproduction is very important for all organisms. Living organisms reproduce to produce young ones like them. Had the process of reproduction not been there, all the plants and animals would have become extinct. So, how do organisms reproduce? Let us go through different types of reproductions among living organisms and understand their implications in carrying genetic information.

Introduction to reproduction

Reproduction is defined as a biological process in which every living organism gives rise to new organisms similar to themselves. Basic features of reproduction include replication of DNA, cell division (only mitotic, or both mitotic and meiotic), the formation of reproductive bodies or units and development of reproductive bodies into offspring.

Types of Reproduction

Reproduction can be broadly classified into two types- asexual reproduction and sexual reproduction.

  1. Asexual Reproduction: A single parent is involved in such kind of reproduction. Individuals reproduced are genetically and morphologically identical to their parents. It is more commonly observed in single-celled organisms along with some plants and animals. Asexual reproduction can be of various types:
  • Binary fission: A parent cell divides into two equal parent cells after replicating genetic material. For example, Amoeba and Paramecium.

  • Budding: The new organism or bud matures while attached to the parent. After maturation, the organism detaches from the parent body and lives an independent life. For example, Hydra and Yeast.
  • Fragmentation: A new organism is formed from the fragment of the parent. The fragment is formed by splitting of the parent plant. For example, cyanobacteria, lichens and moulds.
  • Parthenogenesis: A new organism is produced from the unfertilized egg.
  • Vegetative reproduction: It does not involve the production of seeds or spores for the propagation of new plants. For raising new plants, vegetative parts of plants such as runners, rhizomes, suckers, tubers, etc. can be used.
  1. Sexual Reproduction: Sexual reproduction involves male gamete and female gamete. Male and female gametes fuse to form a zygote. The zygote will then go through a process of various divisions to generate a new organism. The offspring contains genetic material from both the parents, that is, half number of chromosomes from the mother and half chromosomes from the father.

There are different phases of sexual reproduction:

  • Juvenile phase – Phase of growth and maturity before a person reaches reproductive maturity.
  • Reproductive phase– Phase when a person reaches sexual maturity. During reproductive phases, female mammals undergo a cycle known as the menstrual cycle. Apes undergo oestrus cycle.
  • Senescent phase– End of the reproductive phase. It is marked with the death phase.

Sexual or Asexual mode of reproduction

Sexual reproduction is an advanced mode of reproduction. Two individuals of opposite sex are involved here and it allows the formation of new variants by the combination of the DNA from those two different individuals. This process involves the fusion of the male and the female gamete. This, in turn, produces variants, which are not identical to their parents and to themselves. This variation aids the individual to get adapted and acclimatized to constantly changing and challenging environments. Also, it causes the evolution of better-adapted organisms which is suitable and necessary for the greater survival of a species. On the contrary, asexual reproduction allows very little or no variation at all. As a result, the individuals produced are exact copies of their parents and themselves.

Significance of reproduction

  1. It allows fulfilling the cycle of the life In this sense, reproduction is an element relevant to the cycle of life because it allows the birth of new individuals, which will then be reproduced giving rise to other individuals, and so on.
  2. Reproduction is the only method to guarantee the existence of a relay generation. It prevents extinction and further ensures the continuity of the species.
  3. It allows transmitting the characteristics of the parents to the children i.e. inheritance. The deoxyribonucleic acid (DNA) contains the unique properties and characteristics of the individuals which are transmitted from one generation to another.
  4. At the same time, it allows creating variations in the species since the individuals are produced who have half the genetic load of their father and half of the genetic load of their mother.
  5. Asexual reproduction allows in creating genetically modified crops and hence has immense importance in the agricultural field. For example, there are special seeds produced by asexual reproduction to resist certain conditions

Higher organisms have resorted to sexual reproduction in spite of its complexity

New variations in progenies are introduced by the mode of sexual reproduction through the combination of the DNA from two (usually) different individuals. These variations aid the individual to cope with various environmental conditions and thus make the organism better suited for the environment. Evolution of better organisms and therefore, provide better chances of survival are also caused by the variation. On the other hand, asexual reproduction is the primitive mode and it does not provide genetic differences in the individuals produced.

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