Science — CBSE Class 10 board question

Not all multicellular organisms can reproduce through fragmentation or regeneration because of their complex body organisation.

In simple multicellular organisms like Spirogyra or Planaria, the body organisation is relatively simple, so each fragment contains enough information and cell types to grow into a complete individual.

However, in complex multicellular organisms, specialised cells are organised into tissues, tissues into organs, and organs are placed at definite positions in the body. Such a carefully organised body cannot simply divide cell-by-cell into fragments, as each fragment would not have all the necessary tissues and organs to develop into a new individual.

Therefore, complex multicellular organisms require more specialised modes of reproduction involving specific reproductive cell types, rather than simple fragmentation or regeneration.

Source: Chapter 7, Sections 7.2.2 (Fragmentation) and 7.2.3 (Regeneration)

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• The examiner expects two key ideas: (1) simple multicellular organisms can do it because of simple organisation; (2) complex ones cannot because cells are specialised into tissues and organs in a definite arrangement.
• Mention Spirogyra/Planaria as examples of those that can, to show contrast.
• The phrase "not simply a random collection of cells" from the textbook is the core reasoning — paraphrase it clearly.
• Avoid writing vague answers like "they are complex"; explain why complexity is the barrier.