Introduction
Every organism of our biosphere has the most natural and fundamental characteristic to produce like themselves and carry forward the generation of their species continously through a process called reproduction. the organ through which reproductive activities in the living being are performed are called reproductive organ and all the reproductive organs form a reproductive system.
हमारे जीवमंडल के प्रत्येक जीव में सबसे प्राकृतिक और मौलिक विशेषता है कि वह अपनी तरह का उत्पन्न करता है और प्रजनन नामक प्रक्रिया के माध्यम से अपनी प्रजातियों की पीढ़ी को लगातार आगे बढ़ाता है। वह अंग जिसके द्वारा जीवों में जनन क्रियाएँ संपन्न होती हैं, जनन अंग कहलाते हैं और सभी जनन अंग एक जनन तंत्र का निर्माण करते हैं।
- The adult who give rise to young ones are calles parents.
- The young ones are called daughter or offspring ( both singular & plural).
Reproduction ( procreation , breeding)
- Reproduction can be defined as the biological process by which new individual organism (offspring) of the same kind (same characteristics as their parents) are produced from the parents.
- Its aim is that to continued exixtence of the species.
- It helps in maintaining a proper balance among various biotc constituents of the ecosystem.
- The basic event in reproduction is the creation of DNA copy.
- Cells use chemical reactions to build two copies of DNA in a reproducing cells.
- In additional ,DNA copying is accompanied by creation of an additional celluar apparatus.
- Then each DNA copy is separated with its own celluar apparatus.
- Effectively , a cell divides to give rise to two cells.
- प्रजनन को जैविक प्रक्रिया के रूप में परिभाषित किया जा सकता है जिसके द्वारा माता-पिता से एक ही तरह के नए व्यक्तिगत जीव (संतान) (उनके माता-पिता के समान लक्षण) उत्पन्न होते हैं।
- इसका उद्देश्य प्रजातियों के निरंतर अस्तित्व के लिए है।
- यह पारिस्थितिकी तंत्र के विभिन्न बायोटेक घटकों के बीच उचित संतुलन बनाए रखने में मदद करता है।
- प्रजनन में मूल घटना डीएनए कॉपी का निर्माण है।
- कोशिकाएँ एक पुनरुत्पादक कोशिकाओं में डीएनए की दो प्रतियाँ बनाने के लिए रासायनिक प्रतिक्रियाओं का उपयोग करती हैं।
- अतिरिक्त में, डीएनए की प्रतिलिपि के साथ एक अतिरिक्त सेल्युअर उपकरण का निर्माण होता है।
- फिर प्रत्येक डीएनए कॉपी को अपने स्वयं के सेल्युअर उपकरण से अलग किया जाता है।
- प्रभावी रूप से, एक कोशिका विभाजित होकर दो कोशिकाओं को जन्म देती है।
Note - The reproduction cells show mitotic and meiotic division. Each mitotic division result in two daughter cells whereas meiotic division results in four daughter cells that are called gametes. these gametes have only half the number of chromosomes (haploid).
प्रजनन कोशिकाएं समसूत्री विभाजन और अर्धसूत्रीविभाजन दर्शाती हैं। प्रत्येक समसूत्री विभाजन के परिणामस्वरूप दो संतति कोशिकाएं होती हैं जबकि अर्धसूत्रीविभाजन के परिणामस्वरूप चार संतति कोशिकाएं होती हैं जिन्हें युग्मक कहा जाता है। इन युग्मकों में गुणसूत्रों (अगुणित) की संख्या केवल आधी होती है।
Function of reproduction -
1. Continuity of species - A species continues to live indefinitely because of the reproduction of its inviduals.
2. Replacement - It replaces individuals dying due to sentences or ageing, predation and disease.
3. population organisation - It maintains population organisation consisting of young, adults and aged individuals.
4. Life - Life can exist on earth only if there is reproduction of living organism.
5. Variation - Reproduction introduces varition in structure , function and behaviour. They produce individuality of living beings.
6. Useful Variation - Useful Variation persist in the individuals. They are transfered to new generations. Useful Variation help in adaptation and evolution.
Types of Reproduction
Through basic principles of reproduction are similar in all organism, the mechanism to multiply and produce offspring shows large diversity. it is due to difference in their organisation , structure , physiology and habitat.
There are two main metods of reproduction in living organism these are
1. Asexual reproduction ( अलैंगिक प्रजनन )
2. Sexual reproduction ( लैंगिक प्रजनन )
1. Asexual reproduction -
- When the offspring is produced from a single parent by mitotic cell division or no gamete formation takes place and not involves fusion of sex cells the method is called asexual reproduction .
- Meiosis has no role in it.
- All the individual formed through asexual reproduction from a parents are morphologically and genetically similar to one another as ell as their parent they are called clone.
- It is common among lowly organised living being for ex - unicelluar organism, simple plants and simple animals.
- it is absent in higher invertebrates and vertebrates.
Types of Asexual reproduction
Asexual reproduction occurs by fission , budding, fragmentation,regeneration, parthenogenesis, vegetative propagation, propagation by tissue culture.
Fission - ( L. fissus - cleft )-
It is mode of asexual reproduction in which body of a mature individual divides in to two or more similar and equal sized daughters. In unicelluar organism, protists and moneras, cell division results infission.Therefore , it is the mode of asexual reproduction in them . fission can occur by binary , multiple and plasmotomy fission.
Binary Fission :-
It is division of the body of an individual in to two equal halves, each of which functions as an independent daughter individual. In unicelluar organisms , binary fission is accompanied by mitotic karyokinesis (division of nucles ) followed by cytokinesis (division of cytoplasm or cell). In metazoans the multicelluar individual divides in to two daughters by a sort of construction or cleavege. The organism showing binary fission seldom die of sentence or old age because as soon as they mature, they divide in two daughters. They are , therefore , nearly immortal . Depending upon the plane . Binary fission is of the following types
