Reproduction

 

Reproduction is a mechanism in living organisms to perpetuate their species . 

👪Reproduction is production of new beings from existing beings of a species . 

🧑‍🍼Reproduction may or may not be characteristic of all living organisms . For eg. in mules reproduction does not occur as they don't produce gametes . They are hybrid offspring of donkey and horse .

🤱Reproduction may or may not require presence of opposite sexes ( male and female ) . This sounds bizarre as we are ourselves product of both parents . In some animals like honey bee , rotifers , whip-tailed lizard production of male or female does not require fertilisation of sperms and ova . Only one gamete develop further into offspring without undergoing doubling of chromosomes . 

👪This phenomenon of parthenogenesis does not induce variations like sexual reproduction does .

🧑‍🍼Question arises why nature has not selected only one mode of reproduction . Why it has maintained both asexual and sexual modes of reproduction. 

🧑‍🍼If we analyse these modes we find that sexual mode of reproduction has been successfully implemented by higher forms of life with some degree of asexual reproduction in same or different species . For instance honey bee queen can perform both sexual and asexual mode by allowing fertilisation of its gamete to produce female offspring and allowing development of its haploid eggs into haploid drones without fusion with sperms. However ploidy will be different in different castes of bees . Drones will be haploid with 16 chromosomes and females will be diploid with 32 chromosomes. 

🦎In whiptailed lizard story is entirely different. They have no male being only females are produced from haploid eggs which can themselves produce eggs on sexual maturity . These haploid eggs then develop parthenogenetically into female lizards.

🦃Variation in case of asexual reproduction will be far lesser than that in sexual reproduction . Parthenogenesis is also no exception . 

🦇Many organisms are entirely sexually reproducing and lack any of such asexual forms that is seen in rotifers , drones and whiptailed lizards.

🦆Variation in species is beneficial in case current environment changes which may become unfavourable to most of the individual but some of the variants will be successful in tiding over these harsh conditions and propagate the species further. 

🥦Same is true with plants which have evolved along with animals on same planet . I don't need to mention ice ages and great extinction on earth .