Reproduction is a process of continuation of a living species. 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 types as 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 set of chromosomes. The union of gametes occurs to form a zygote which transform to embryo and then modifies to organism.
Differences between sexual and asexual reproduction
|Differences||Asexual reproduction||Sexual reproduction|
|Zygote||Is never formed||Formed by union of male & female gamete|
|DNA||Is Diploid (two set of chromosomes)||Haploid gamete unite to form diploid|
|Evolution Significance||Is not advanced type||Advanced phenomenon|
|The progeny||Offspring genetically identical to parent||Different but have better features better and similar to parents|
|Cell division||By mitosis (1=2) type cell division||cells which make gamete under fo division by meiosis (1=4)|
|Occurrence||Common in lower form like bacteria, fungi, protzoan’s etc.and absent in higher organisms in evolution tree||Present in both lower and higher form of organisms.|
|Progeny||Healthy or little healthy||Very healthy|
|Life span||They are considered immortal||They are mortal|
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 forms of progeny among all the animals as male and 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).