Question

Asexual reproduction involves a single parent to produce offspring without the formation of gametes. It occurs by the following ways: Fission, Budding, Fragmentation, Spore formation and Regeneration. In one of the methods like regeneration, Planaria A is cut horizontally into three pieces – L, M and N and Planaria B is cut vertically into two equal halves – O and P.

(a) Which of the cut pieces of the two Planaria could regenerate to form a complete organism?
(b) Give an example of another organism which follows the same mode of reproduction as Planaria.
(c) What is the meaning of ‘development’ in regeneration?
OR
(c) Differentiate between regeneration and fragmentation.

Answer 1

Detailed explanation of Planarian regeneration and its comparison to fragmentation:

Step 1: Understanding Planarian Regeneration
(a) Any section of a Planarian, when cut, can develop into a full organism.
- This capability stems from Planaria's remarkable regenerative capacity.
- Specialized stem cells known as neoblasts are responsible for regrowing lost body parts.

Step 2: Other Regenerative Organisms
(b) Hydra is another organism exhibiting regeneration.
- Similar to Planaria, Hydra can regenerate its entire body from small fragments.
- This is also attributed to the presence of regenerative cells.

Step 3: The Regeneration Process
(c) Regeneration is a biological development process comprising:
- Proliferation: Cell growth and division.
- Differentiation: Cells developing specific functions.
- Organization: Cells arranging to reconstruct the organism's structure and function.

Step 4: Regeneration vs. Fragmentation Comparison

Regeneration	Fragmentation
A portion of an organism regenerates into a whole organism.	The body splits into fragments, each becoming a new individual.
Involves specialized cells (e.g., neoblasts).	Does not require specialized cells.
Example: Planaria	Example: Spirogyra

Concluding Remark:
Regeneration differs from fragmentation. Regeneration is a complex process involving cell specialization and organization, whereas fragmentation is a simpler process where each fragment grows autonomously into a new organism.