Question

Assertion : Due to fragmentation in Planaria, each part develops the remaining body parts and becomes a complete animal.
Reason : Differentiated tissue present in each broken part of Planaria undergoes dedifferentiation and then differentiation in regeneration.
a) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
b) Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
c) Assertion is correct but the Reason is incorrect.
d) Both Assertion and Reason are incorrect.

Answer 1

Hint:Regeneration is the ability of the body to regrow its lost body parts. This regeneration capability is present only in some animals. Some animals use this regenerative ability as a defence mechanism against predators and some use it as a form of asexual reproduction.

Complete Answer:
Planaria has the capability to regenerate itself by the process of regeneration. When the body of Planaria is cut into different segments, the place through which it is cut forms a blastema. This blastema helps in the regeneration of the body of the organism into a whole. From each differentiated segment, the whole body of Planaria is formed. These newly formed Planaria are the daughters. They are identical to their parents and are their exact copies. The formation of planaria by this method is called its asexual mode of reproduction. They usually segment their body in such a way that a greater number of progenies can be formed. In them, the process of regeneration does not involve redifferentiation and dedifferentiation of the cells. The types of regeneration include morphallaxis, epimorphosis, heteromorphosis, super regeneration and wolffian regeneration. In morphallaxis, partial regeneration occurs and the organism is left to grow on its own when it will feed and grow naturally. In this, the lost part gets regenerated in a very slow process. In epimorphosis, the dedifferentiation of the cells occurs to form the mass of the cells which are undifferentiated in nature. They are rudiment and slowly transform into the lost limb.
Thus, the right option is B.

Note: The regeneration capability is seen in some of the amphibians and hydra. Animals such as lizards usually lose their tails when they are in conditions that pose danger to them. The cells present at the point of detachment usually dedifferentiate to form the tail of the organism.