Question

Why are budding, fragmentation and regeneration all considered as asexual types of reproduction? With neat diagrams explain the process of regeneration in Planaria. 

Answer 1

Asexual reproduction is a type of reproduction in which new organisms are formed from a single parent.

In budding, new organism is formed as a bud from the single parent cell. A bud or a protrusion develops as an outgrowth due to repeated cell division at one specific site and develop into tiny individuals. After maturation, it detaches from the parent body and becomes a new independent individual. 

On the contrast, in fragmentation, when an organism attains maturity, the parent body breaks down into a smaller pieces or fragments. Each fragment grows into a new organism.

While, in regeneration, an individual is cut into many pieces accidentally, each piece grows into a new individual.

In all these three modes of reproduction a single parent is involved so these are considered as types of asexual reproduction.

Regeneration in Planaria -

Planaria can be cut into a number of pieces and each piece grows into a complete organism. This is known as regeneration. In the diagram below, the body of the Planaria is cut horizontally into three pieces and each piece regenerates into a new organism.