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Difference between Asexual Reproduction and Sexual Reproduction

There are two methods of reproduction –
(A) Asexual reproduction
(B) Sexual reproduction

(A) Asexual reproduction

  • It involves only one individual (single parent). It takes place without gametes (sex cells) and fertilization.
  • Cells divide mitotically. It is a simple process of cell division as shown below.

  • Offsprings are genetically identical to the parents.
  • E.g. Spirogyra reproduces by fragmentation, amoeba and bacteria reproduce by binary fission, yeast and hydra reproduce by budding, planaria reproduces by regeneration, flowering plants such as rose reproduce by vegetative propagation, rhizopus fungus reproduces by spore formation.

Advantage

  • It is a simple and a rapid mode of multiplication.

Disadvantage

  • Lack of genetical variations as offsprings are genetically identical to the parent.

(B) Sexual reproduction


  • The male sexual unit is called male gamete.         
  • Male gamete in animals – Sperms
  • Male gamete in flowers – pollen grains    
  • The female sexual unit is called female gamete or ova.

  • It involves the union / fusion of male and female gametes (two parents) to form a zygote.
  • It occurs by two main processes-

(a) Meiosis – It is a type of cell division in which chromosomes divide into half (2n → n ) and further result into formation of haploid gametes.


(b) Fertilization
– It is the fusion of nuclei of male and female gametes to form a zygote (diploid 2n ) from which a new individual can develop.


Advantages

  1. It promotes genetic diversity in a species.
  2. Sexual reproduction improves the chances of survival of the species at times of drastic changes in environmental conditions.
  3. It results in new combination of traits / genes by the gametes and this reshuffling increases genetic variations.
  4. These variations help in the origin of new species (evolution).
  5. Variations induced in a species also help to eliminate unwanted characteristics from the population.

  • If fertilization occurs outside the body of the organism, it is called external fertilization. E.g. Frogs, fishes.
  • If fertilization occurs inside the body of the organism, it is called internal fertilization. E.g. Birds, mammals.
  • In animals, the male and female gametes are generally produced in separate individuals. In certain animals, both sex organs (male and female) occur in a single individual. Such animals are called hermaphrodites. Ex. Snail, tapeworm.
  • In plants, the sexes may or may not be separate. A flower may be –
    unisexual – bearing either male or female gamete e.g. watermelon, papaya.
    bisexual – bearing both gametes e.g. hibiscus, mustard.

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Asexual Reproduction