Reproduction in Organisms

Reproduction is a process in which organisms produce offspring of the same species. The offspring grow,and produce new offspring. Thus, there is a process of birth, growth and death. Genetic variation is occured or is inherited during the process of reproduction.  It’s one of the most important fundamental characteristics of living organisms. It involves the transmission of genetic material (genetic information) from one generation to the another, ensuring that the species survives over long periods of time.

Reproduction 

As stated earlier reproduction is a biological and chemical process in which an organism gives rise to offspring which one similar to itself. It is a very important characteristic for all the living organisms.

Purpose of reproduction

  • Continuity of species : Reproduction maintains the continuity of species for a long term
  • Population organisms : Reproduction maintains population for all the living organisms
  • Variation : Reproduction introduces variation in the organisms due to change in genes

Types of Reproduction 

Two main types of reproduction are found in animals 1.asexual and 2.sexual.

Asexual reproduction

Formation of organisms from parent or without the involved of gamete formation, the reproduction is called asexual. As a result, the offspring that are produced are not only similar to one another but are also exact copies of their parents. Clone is a group of morphologically and genetically similar individuals.

Characteristics of Asexual Reproduction

  • A single parent is involved
  • Gametes are not formed
  • No fertilisation
  • Multiplication occurs rapidly
  • There is only mitotic cell division

Type of Asexual Reproduction

  • Fission: In unicellular organisms such as bacteria or multicellular animals , asexual reproduction occurs by process called fission

Ex :- amoeba, plasmodium etc

  • Strobilation: It is a modified form of transverse fission, in which a series of ring like transverse constructions are developed, so that the organism resembles a pile of minute saucer or discs, placed one above the another. The segment body is called a strobila. Ex :- Aurelia, Taenia (Tapeworm)
  • Budding: In budding ,a daughter individual is formed from a small projection from the parental body (bud) 
  • Fragmentation: The phenomenon of breaking of body into several fragments, and later developed into complete organism
  • Vegetative reproduction : The reproduction present in plants is termed as vegetative reproduction. When new individuals formation takes place without seeds or spores, vegetative reproduction arises
  • Agamogenesis : Reproduction that does not have involvement of male gamete is termed as agamogenesis. Agamogenesis includes parthenogenesis and apomixis

Sexual Reproduction 

It’s the process of production of new individuals (after gamtogenesis) through the formation and fusion of male and female gametes. Sexual reproduction is also called amphimixis or syngenesis, amphigony. 

Characteristics of Sexual reproduction 

  • It’s usually biparental (involving two parents)
  • Gametes are always formed and involved
  • Fertilization takes place after two gametes formation take place
  • It involves both meiosis and mitosis
  • Multiplication is not so rapid
  • Offspring genetically differ from the parents

Type of Sexual reproduction

    • Syngamy : It is the complete and permanent fusion of male and female gametes to form the zygote. Syngamy is of two types:-
      1. Endogamy :- In endogamy, two types of gametes fertilise that are formed by the same parent. Ex :- Taenia 
      2. Exogamy :-  The fusion of gametes from distantly related or unrelated organisms, i.e. Rabbit etc .
    • Conjugation:- The transfer of genes or genetic information from one prokaryotic cell to another by a mechanism . Two individual cells are united by a tube formed by outgrowths from one or both cells.It corresponds to cross fertilisation of higher animal. Ex – Paramecium, Spirogyra, etc.

Fertilisation 

The fertilisation is the complete and permanent fusion of the two gametes from different parents or from the same parents to form a diploid zygote. This process is also called syngamy. Fertilisation occurs two type :- 

      • External fertilisation :-Formation of zygote after fertilisation outside the body of the organism, this type of gametic fusion is called external fertilisation or external syngamy.  It occurs in water for this type of fertilisation . Ex :- bony fish or frog
      • Internal fertilisation :- When egg is formed inside the female body when it’s fuses with the male gamete, the process is called internal fertilisation or internal syngamy.ex :- reptiles, birds , mammals and majority bryophytes, pteridophytes etc.

Conclusion 

Reproduction plays a major role in the production of younger ones with the help of parent, depending upon the phenomenon reproduction can be sexual and asexual also reroduction can arise in both plans and human beings. Various types of asexual reproduction are present. In case of animals they can reproduce sexually as well as asexually.

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