Question

Which is the correct example of the type of regeneration out of the two major types?
a. Morphallaxis- Regeneration of two transversely cut equal pieces of one Hydra into two small Hydras
b. Epimorphosis- Replacement of old and dead erythrocytes by the new ones
c. Morphallaxis- Healing of wound in the skin
d. Epimorphosis- Regeneration of crushed and filtered out pieces of Planaria into as many new planarians

Answer 1

The natural phenomenon of replacing or repairing, in plants and animals, damaged or missing cells, tissues, organs and even whole parts of the body to full function. Regeneration research for its future applications in medicine, such as the treatment of a number of injuries and diseases, is being performed.

Complete answer:

Option A is correct. Morphallaxis and Epimorphosis are two forms of regeneration. Any cut part of the organism in Morphallaxis regenerates into the entire organism. Planaria and Hydra, for instance, can regenerate from a cut portion into an entire species. The classical example of morphallaxis is that of the Cnidarian hydra, where the remaining severed parts form two completely functioning and separate hydra when the animal is severed in two (by deliberately cutting it with, for example, a surgical knife).

Option B is incorrect. The cut or wounded part of the organism is healed in Epimorphosis. For instance, Lizard’s repairs itself when cut down. Epimorphosis restores the organism's anatomy and the original polarity that existed prior to the tissue and/or structure of the organism being killed.

Option C is incorrect. Morphallaxis, which is distinguished by a much greater relative degree of cell proliferation, is often contrasted with epimorphosis. While cellular differentiation is active in both processes, the majority of regeneration in morphallaxis is due to reorganisation or exchange, while the majority of regeneration in epimorphosis is due to cellular differentiation.

Option D is incorrect. In a way that includes extensive cell proliferation of somatic stem cells, dedifferentiation, and reformation, as well as blastema formation, epimorphosis is characterised as the regeneration of a specific part of an organism. It can be considered a basic development model, but it only occurs in tissues surrounding the injury site instead of occurring system-wide. For both vertebrates and invertebrates, epimorphosis regeneration may be observed, such as the common examples: salamanders, Annelida, and planarians.

Hence, the correct answer is option (A).

Note: The noteworthy characteristic of morphallaxis is that a vast majority of regenerated tissue originates in the organism from tissue that is already present. That is, the hydra's one severed segment shapes into a smaller version of the original hydra, around the same size as the segment being severed. There is, therefore, a tissue 'exchange' occurs.