Reproduction is a process of continuation of a living species. This continuation happens by giving birth to progeny or offspring by the adult animal.
This continuation happens by giving birth to progeny or offspring by the adult animal.
Reproduction is the only way of multiplication of population for all the living organisms.
This phenomenon extends from single cell animal to multi-cellular organisms.
The process of reproduction occurs by two means viz. asexual reproduction & sexual reproduction.
Asexual reproduction is one which occurs when one living organism gives birth to its progeny without the help of another organism of its own kind.
Sexual reproduction is quite different and is one which occurs when one animal (or plant) gives birth to its progeny by the help of another animals of its own kind.
Asexual reproduction occurs by means of either binary fission (bacteria, protozoans), or by segmentation (in fungi, algae) and budding (hydra) etc.
Sexual reproduction occurs by means of exchange of male and female gametes between parent animals. In animals there is specialized male and female organs while in plants there are flower containing stamens (male organ) and stigma (female organ) for the purpose.
Here there is exchange is gametes one from the male counter part and other from the female counter part. So the gametes are termed as male gamete and female gamete.
Both of these gametes have haploid (1x) set of chromosomes. The union of gametes occurs to form a zygote which diploid (2x).This zygote transforms to embryo and then modifies to organism.
As one goes upwards in the evolution tree, there is absence of asexual reproduction in higher plants and animals. While only the lower forms reproduce asexually.The difference between sexual and asexual reproduction is small. But the effect is quite heavy in terms of the characters of the progeny born.
So asexual reproduction is limited to lower forms like bacteria, fungi, algae and protozoans.
Interestingly reproduction phenomenon gives rise to two distinct characters among animals and plants. This character is, an animal can be either male or female.
In plants this is quite uncommon. There can be plants as male plant and female plants and sometimes both male and female gametes are formed in same plant. There can also be differences in the same plant as male and female flowers to indicate differences. Again in the same flower there can be both male and female organs.
Among animals one can see this type of possession of both male and female sex organs is seen in hermaphrodites. Some examples include, earthworms, snails (molluscs) etc. This is absent in vertebrates (animals with vertebral column).
Difference Between Sexual and Asexual reproduction
The key differences are as mentioned in the table below.
|Charector||Asexual reproduction||Sexual reproduction|
|Seen in||Lower forms like bacteria||Seen in all higher plants and animals|
|Gametes||No gametes are formed||Male and female gametes are formed|
|Cell division involved||Only mitosis type of cell division occurs||Meiosis type of cell division is involved, then mitosis continues.|
|Offsprings||Are identical to parents and lack robustness.||Are a bit different to parents but are more healthy and robust.|
|Prevalance||Present in less number of living forms||Present in most number of living organisms.|
|Genetic material||The genes and genetic material are just multiplied and passed on to new organisms from parent.||The genetic material undergoes inter mixing from both parents to form a new set of genetic material.|
|Reproductive organs||Are not present or needed.||Prominent male and female reproductive organs are present.|
Also after reproduction, animals take care of their siblings till they mature and survive on their own. This is not required by organism born by asexual methods.