Question

The type of asexual reproduction found in hydra is
A) Multiple fission
B) Budding
C) Sporulation
D) Binary fission
E) Gemmule formation

Answer 1

Hint:Hydras are fresh-water animals belonging to the phylum Cnidaria. They are extensively studied for their regenerative potential. Under conditions of abundant food, cells of the existing animals divide to form a bud which develops into a miniature adult and then gets detached from the older parent.

Complete answer:
>When new individuals are produced from an existing individual such that the new ones are genetically identical to the pre-existing organism (except for the somatic mutations) this is called asexual reproduction. Multiple ways in which organisms can reproduce asexually are gemmule formation, budding, and fission both binary and multiple.
>In binary fission one animal gets divided to form two daughters. First the DNA making up the genome of the parent cell is replicated to make two copies of genomes. This is followed by dividing the genomic and cytoplasmic components to produce two daughter cells identical in size to the parent. Most prokaryotes such as bacteria and eukaryotes like tapeworms and syphostome polyps reproduce by this method. In tapeworms depending on the axis of cell separation fission can be transverse or axial.
>Multiple fission is commonly seen in eukaryotes such as protists. Here the nucleus of the parent cell divides many times to form multiple nuclei each of which then accumulates some cytoplasm and gets separated by membranes to form new daughters. Often daughters are not identical to the parent.
>Sporulation is the process by which vulnerable vegetative cells produce resistant cells which can then germinate to new organisms in favourable conditions. Both prokaryotic bacteria and eukaryotic protists can form spore.
>Gemmule formation is the mode of asexual reproduction in sponges. Gemmules are a type of endogenous bud, resistant to hostile conditions of temperature, desiccation, and anoxia. In favourable conditions gemmules can give rise to new organisms.
>Budding is a process in which new organisms are formed from parents as an outgrowth following repeated rounds of cell division. The new bud then gets detached from the parent to form new individuals. Unicellular yeasts and multicellular hydra use this method to divide asexually. Buds can be endogenous or exogenous.

>Besides Hydra, budding is a common mode reproduction in different cnidarians like corals, sea anemones, jellyfishes. Hydra use regenerative cells to form buds under conditions of abundance of food.

Hence the correct answer is option ‘B’.

Note:Asexual reproduction is the mode of reproduction in all prokaryotes and several pathogenic eukaryotes (Plasmodium sp., Giardia sp., Leishmania sp.) as well. In case of hydra asexually reproduction is favoured in low population density and hence abundant resource. In case of crowding or food scarcity hydras reproduce sexually to increase genetic diversity and this in turn help the sexually reproduced progeny to utilise unexplored niches and adapt to newer environments.