How Whittaker classification not based on mode of reproduction ...???

If you notice clearly that the categorization goes only based on the evolutionary perspective.

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Demerits of five- Kingdom Classification:Although this system is considered to be an advanced system stillobjections have been raised against this, which is following.

• It fails to distinguish between archaebacteria and eubacteria.
• The kingdom- Protista is a highlyheterogeneous group of organisms, which seems to be havingpolyphyleticevolution.
• Placement of algae on the basis of the degreeof the cellularorganization into different kingdoms appears to be unrealistic.
• Red and brown algae placed in kingdom – Plantaeisnot related to other members.
• Viruses an important form of life has not been considered in this system of classification.